THEORY OF ELECTRON-MOLECULE COLLISIONS

FOR ASTROPHYSICS, BIOPHYSICS AND LOW TEMPERATURE PLASMAS:

OPPORTUNITIES AND CHALLENGES

December 3-5, 2012

ORGANIZERS: Viatcheslav Kokoouline, University of Central Florida Chris Greene, Purdue University

Sponsored by:

Institute for Theoretical Atomic, Molecular and Optical Physics*

Harvard - Smithsonian Center for Astrophysics

60 Garden St., Cambridge, MA

http://www.cfa.harvard.edu/itamp/Theory-of-Electron-2012.html

Abstract Booklet and Program

*Sponsored by National Science Foundation

Molecular Frame Photoelectron Angular Distribution of Carbon K-shell in C2H4 Courtesy of Douguet, Kokoouline, Fonseca dos Santos, Rescigno and Orel

 

TABLE OF CONTENTS

1

TABLE OF CONTENTS PARTICIPANTS .......................................................................................................................................................... 3

PROGRAM ................................................................................................................................................................... 5

ABSTRACTS

DATA NEEDS OF ELECTRON-MOLECULE COLLISIONS IN FUSION APPLICATIONS ........................................ 7

H.K. CHUNG AND B.J. BRAAMS

TIME-RESOLVED MOLECULAR FRAME PHOTOELECTRON ANGULAR DISTRIBUTION (MFPAD) IN

ACETYLENE AND ETHYLENE ISOMERIZATIONS /SIMPLE MODEL TO DESCRIBE THE DISSOCIATIVE

RECOMBINATION OF POLYATOMIC IONS OF ASTROPHYSICAL INTEREST ................................................. 8 N. DOUGUET, V. KOKOOULINE, S. FONSECA DOS SANTOS, T. N. RESCIGNO, A. E. OREL

THEORY OF DISSOCIATIVE ELECTRON ATTACHMENT: BIOMOLECULES AND CLUSTERS ...................... 10

ILYA I. FABRIKANT

SIMPLIFIED MODEL TO DESCRIBE THE DISSOCIATIVE RECOMBINATION OF POLYATOMIC IONS OF

ASTROPHYSICAL INTEREST ....................................................................................................................... 12 S. FONSECA DOS SANTOS, N. DOUGUET, V. KOKOOULINE, A. E. OREL

THEORETICAL STUDIES OF DISSOCIATIVE RECOMBINATION ................................................................. 13

STEVEN L. GUBERMAN

SUCCESSES AND CHALLENGES OF FRAME TRANSFORMATION THEORY ................................................. 15

CHRIS H. GREENE

THE R-MATRIX METHOD FOR ATTOSECOND SPECTROSCOPY ............................................................... 16 A. G. HARVEY, F. MORALES, O. SMIRNOVA

ANGULAR DEPENDENCE OF DISSOCIATIVE ELECTRON ATTACHMENT TO METHANOL ........................ 18

DANIEL J. HAXTON

DISSOCIATIVE RECOMBINATION AND ELECTRON ATTACHMENT IN THE INTERSTELLAR MEDIUM ..... 19

ERIC HERBST

THEORETICAL METHODS FOR TREATING STABLE ANIONS FOR WHICH THE EXCESS ELECTRON DOES

NOT BIND IN THE HARTREE-FOCK APPROXIMATION ............................................................................. 20 K. D. JORDAN AND V. VOORA

ANALYTIC THREE-CHANNEL MODEL FOR RESONANCE-AVERAGED DIRECT AND INDIRECT

DISSOCIATIVE RECOMBINATION PROCESSES OF MOLECULAR IONS ...................................................... 21 I. F. SCHNEIDER, N. POP, AND CH. JUNGEN

RADIATIVE ELECTRON ATTACHMENT TO MOLECULES OF ASTROPHYSICAL INTEREST. BENCHMARK

STUDY OF CN-……………………………………………………………………………………………………………. 22

KOKOOULINE, N. DOUGUET, S. FONSECA DOS SANTOS, O. DULIEU, M. RAOULT, A. E. OREL

DISSOCIATIVE RECOMBINATION MEASUREMENTS.AT ION STORAGE RINGS: ACHIEVEMENTS AND

PERSPECTIVES ............................................................................................................................................ 24 HOLGER KRECKEL

TABLE OF CONTENTS

2

COMPLEX-SCALED EQUATION-OF-MOTION COUPLED-CLUSTER METHOD WITH SINGLE AND DOUBLE

SUBSTITUTIONS FOR AUTOIONIZING EXCITED STATES: THEORY, IMPLEMENTATION,

AND EXAMPLES ........................................................................................................................................... 25 ANNA KRYLOV

PHOTOIONIZATION IN THE MOLECULAR FRAME ..................................................................................... 26 ROBERT R. LUCCHESE

MOLECULAR ANIONS IN THE LABORATORY AND IN SPACE ..................................................................... 27 MICHAEL C. MCCARTHY

LOW-­ENERGY ELECTRON-­MOLECULE COLLISIONS WITH THE SCHWINGER MULTICHANNEL

METHOD† ................................................................................................................................................... 28 VINCENT MCKOY

VERY LOW-ENERGY ELECTRON-INDUCED DAMAGE OF DNA ................................................................ 29 THOMAS M. ORLANDO

THE DYNAMICS OF RESONANT ELECTRON COLLISIONS WITH CARBON DIOXIDE ................................. 31

T.N. RESCIGNO

COMPLEX GENERALIZED HARTREE-FOCK ............................................................................................... 32 ERIC J. SUNDSTROM, DAVID SMALL, AND MARTIN HEAD-GORDON

R-MATRIX AND VIBRATIONAL FRAME TRANSFORMATION IN STUDIES OF MOLECULAR

PHOTODETACHMENT ................................................................................................................................. 33

MICHAL TARANA AND CHRIS H.GREENE

BOUND AND CONTINUUM STATES IN ELECTRON – MOLECULE COLLISIONS USING THE R-MATRIX

METHOD ..................................................................................................................................................... 34 JONATHAN TENNYSON

DESIREE: A UNIQUE CRYOGENIC ELECTROSTATIC STORAGE RING FOR MERGED ION-BEAMS

STUDIES ...................................................................................................................................................... 36 R. D. THOMAS

PARTICIPANTS

3

H-K. Chung International Atomic Energy Agency Vienna, Austria H.Chung@laea.org

Alex Harvey Max Born Institute Berlin, Germany

alex.harvey@mbi-berlin.de

Alexander Dalgarno Harvard Smithsonian CFA Cambridge, MA adalgarno@Cfa.harvard.edu

Eric Herbst University of Virginia Charlottesville, VA

eh2ef@virginia.edu

Nicholas Douguet University of Central Florida Orlando, Florida

douguet@physics.ucf.edu

Christian Jungen University of Paris XI Paris, France

christian.jungen@lac.u-psud.fr

Ilya Fabrikant University of Nebraska Lincoln, Nebraska

ifabrikant@unl.edu

Kenneth D. Jordan University of Pittsburg Pittsburgh, PA jordan@imap.pitt.edu

Samantha Fonseca Dos Santos University of California Davis, California sfonseca@usdavis.edu

Jobin Jose Texas A&M College Station, TX jlopez@chem.tamu.edu

Tom Gorczyca Western Michigan University Kalamazoo, Michigan Gorczyca@wmich.edu

Viatcheslav Kokoouline University of Central Florida Orlando, Florida Viatcheslav.Kokoouline@ucf.edu

Chris H. Greene Purdue University West Lafayette, Indiana Chris.greene.jila@gmail.com

Holger Kreckel

Max Planck Institute Heidelberg Germany holger.kreckel@mpi-hd.mpg.de

Steven Guberman Institute for Scientific Research Winchester, MA

slg@sci.org

Anna Krylov University of Southern CA, Los Angeles, CA

krylov@usc.edu

Daniel Haxton Lawrence Berkeley Natl. Laboratory Davis, California

danhax@gmail.com

Jesus Lopez-Dominguez Texas A&M College Station, TX jobin.jose@mail.chem.tamu.edu

PARTICIPANTS

4

Robert Lucchese Texas A&M College Station, TX

lucchese@chem.tamu.edu

Hossein Sadeghpour Harvard Smithsonian CFA Cambridge, MA hrs@cfa.harvard.edu

Mike McCarthy Harvard Smithsonian CFA Cambridge, MA

mmcarthy@cfa.harvard.edu

Eric Jon Sundstrom University of California Berkeley, CA

esundstr@gmail.com

Vincent McKoy California Institute of Technology Pasadena, CA

mckoy@caltech.edu

Michal Tarana Purdue University West Lafayette, Indiana michal.tarana@jila.colorado.edu

Ann Orel University of California Davis, CA

aeorel@ucdavis.edu

Jonathan Tennyson University College London London j.tennyson@ucl.ac.uk

Thomas Orlando

Georgia Institute of Technology Atlanta, GA

thomas.orlando@chemistry.gatech.edu

Rich Thomas University of Stockholm Sweden rdt@fysik.su.se

Thomas Rescigno Lawrence Berkeley Natl. Laboratory Berkeley, CA

tnresigno@lbl.gov

Patrick Thaddeus Harvard Smithsonian CFA Cambridge, MA, pthaddeus@cfa.harvard.edu

PROGRAM

5

Theory of Electron-Molecule Collisions

PROGRAM

Monday, December 3, 2012 Phillips Auditorium

8:30 Morning Coffee

Session I Chair: Viatcheslav Kokoouline

8:45–09:00 Introductory Remarks and Welcome

09:00–09:40 Hyun-Kyung Chung, “Data needs of electron-molecule collisions in fusion applications”

09:40–10:20 Thomas M. Orlando, “Very low-energy electron-induced damage of DNA”

10:20–11:50 Coffee Break

10:50–11:30 Richard D. Thomas, “DESIREE: a unique cryogenic electrostatic storage ring for merged ion-beams studies”

11:30–12:15 Holger Kreckel, “Dissociative recombination measurements at ion storage rings: achievements and perspectives”

12:15–2:00 Lunch Break

Session II Chair: Chris Greene

02:00–2:40 Robert R. Lucchese, “Photoionization in the molecular frame”

02:40–3:20 Vincent McKoy, “Low-energy electron-molecule collisions with the Schwinger multichannel method”

03:20–3:50 Coffee Break

03:50–4:30 Tom N. Rescigno, “The dynamics of resonant electron collisions with carbon dioxide”

04:30-5:10 Ilya I. Fabrikant, “Theory of dissociative electron attachment: Biomolecules and clusters”

5:30 Reception

Tuesday, December 4, 2012 Phillips Auditorium

08:30 Morning Coffee

Session III Chair: Tom N. Rescigno

09:00–09:40 Eric Herbst, “Dissociative recombination and electron attachment in the interstellar medium”

09:40–10:20 Michael C. McCarthy, “Molecular anions in the laboratory and in space”

PROGRAM

6

10:20–10:50 Coffee Break

10:50-11:30 Ken D. Jordan, “Theoretical methods for treating stable anions for which the excess electron does not bind in the Hartree-Fock approximation”

11:30-12:15 Jonathan Tennyson, “Bound and continuum states in electron – molecule collisions using the R-matrix method”

12:15-2:00 Lunch Break

Session IV Chair: Ann Orel

2:00:2:40 Chris H. Greene, “Successes and challenges of frame transformation theory”

2:40:3:20 Michal Tarana, “R-matrix and Vibrational Frame Transformation in Studies of Molecular Photodetachment”

3:20-3:50 Coffee Break

3:50-4:30 Anna Krylov, “Complex-scaled equation-of-motion coupled-cluster method with single and double substitutions for autoionizing excited states: Theory, implementation, and examples”

4:30-5:10 Eric J. Sundstrom, “Complex generalized Hartree-Fock”

Wednesday, December 5, 2012 Phillips Auditorium

8:30-9:00 Morning Coffee

Session V Chair: Ilya Fabrikant

9:00-09:40 Christian Jungen, “Analytic three-channel model for resonance-averaged direct and indirect dissociative recombination processes of molecular ions”

09:40–10:20 Steven L. Guberman, “Theoretical studies of dissociative recombination”

10:20-10:50 Coffee Break

10:50- 11:30 Nicolas Douguet “Time-resolved molecular frame photoelectron angular distribution (MFPAD) in acetylene and ethylene isomerizations”

10:30–12:15 Samantha Fonseca dos Santos, “Simplified model to describe the dissociative recombination of polyatomic ions of astrophysical interest”

12:15-2:00 Lunch Break

2:00:2:40 Daniel J.Haxton, “Angular dependence of dissociative electron attachment to methanol”

2:40:3:20 Alex G. Harvey, “The R-matrix method for attosecond spectroscopy”

3:20-4:00 Viatcheslav Kokoouline “Radiative electron attachment to molecules of astrophysical interest. Benchmark study of CN-”

4:00 Meeting Adjourn

ABSTRACTS

7

Data Needs of Electron-Molecule Collisions In Fusion Applications

H. K. Chung and B. J. Braams

International Atomic Energy Agency, Austria

The divertor of a magnetic confinement fusion experiment plays a critical

role in particle control (pumping of impurities and in a reactor also helium ash) and

the control of high heat load. Plasma is relatively cold and dense in this region since

the plasma interacts with a material boundary. In a part of the region, the plasma

makes a transition to a neutral gas or hydrogen molecules are formed on the walls

and under some conditions also by volume recombination. Molecular processes and

interaction of the plasma electrons and ions with molecules and molecular ions are

critical features of the divertor plasma and their correct treatment, together with

plasma-wall interaction, is important in edge and divertor plasma modelling.

Since 1978, the atomic and molecular (A+M) data unit of the International

Atomic Energy Agency (IAEA) has coordinated international activities to review

progress and achievements in the production of atomic, molecular and plasma-

surface interaction (AM/PSI) data for fusion program, and to encourage

international cooperation in measurement, compilation and evaluation of AM/PSI

data for fusion. The unit organizes coordinate research projects (CRPs) to increase

capabilities of Member States to undertake fusion plasma modelling and simulation

of present and future experiments and reactor designs. In this workshop, the critical

needs of electron-molecule collision data required by fusion modeling will be

described and the current and future activities of the unit on compilation,

production and evaluation of those data will be presented.

ABSTRACTS

8

Time-Resolved Molecular Frame Photoelectron Angular Distribution (MFPAD) in Acetylene and

Ethylene Isomerizations /Simple Model to Describe The Dissociative Recombination of Polyatomic Ions

of Astrophysical Interest

N. Douguet1, V. Kokoouline2, S. Fonseca dos Santos1, T. N. Rescigno3,

A. E. Orel1

Department of Chemical Engineering and Materials Science, University of California at Davis, Davis, CA

956162 Department of Physics, University of Central Florida, Orlando, FL 32816

Lawrence Berkeley National Laboratory, Berkeley, CA 94720

In the first part of this talk, I will discuss how chemical reactions can be

imaged by detection of a photoelectron in the molecular fixed body-frame, following

either valence or K-shell photoionization. These two techniques will be contrasted

considering the isomerization of the acetylene monocation (C2H2+) towards its

vinylidene final structure. Several MFPADs at the most important geometries and

for different photon energies will be presented. Another example of K-shell

photoisomerization will be treated, considering neutral ethylene (C2H4).

Corresponding MFPADs at the main geometries of C2H4, as well as comparison with

available experimental data on ethylene ground state will be given .

In the second part of the talk, I will present theoretical results on the

dissociative recombination of many polyatomic ions of astrophysical interest. Using

a simplified treatment, which captures the key ingredients of the indirect

recombination mechanism, we have obtained theoretical cross sections at low

incoming electron energy in good agreement with available experimental data for

large polyatomic ions, such as H3+, CH3

+, H3O+, HCNH+, NH4+

and N2H+. New

perspectives on the very low energy dissociative recombination of HCO+ will also be

discussed, including the possible role of HOC+ in storage ring experimental results .

ABSTRACTS

9

(a)

(b)

The above figure (a) shows the

averaged carbon K-shell MFPAD of

C2H4 at its twisted geometry (b) in

D2d symmetry. The MFPAD seems to

image the molecular geometry.

The upper panel shows the Jahn-Teller splitting

of triply degenerate states of NH4+

by distortion

along one of its triply degenerate normal mode.

This splitting is responsible for the high

calculated DR cross section (lower panel) in

good agreement with experiments.

This work is supported by the DOE Office of Basic Energy Science and the

National Science Foundation, Grant No's PHY-08-55092 and PHY-08-55622.

ABSTRACTS

10

Theory of Dissociative Electron Attachment: Biomolecules and Clusters

Ilya I. Fabrikant

Department of Physics and Astronomy,

University of Nebraska-Lincoln, Lincoln, NE 68588, USA

Recent renewed interest to the dissociative electron attachment (DEA)

processes has been stimulated by the role of low-energy electrons in radiation

damage and ion-beam cancer therapy. In the present paper we discuss electron-

induced hydrogen loss in a few simple biological molecules: formic acid [1], uracil

[2], thymine, and aminobutanoic acid [3]. The DEA process in these systems is

controlled by shape resonances of the A1 symmetry whose width is very large. Due

to the long-range (dipolar and polarization) interaction between the incoming

electron and the molecule sharp vibrational Feshbach resonances and threshold

cusps appear at the vibrational excitation thresholds.

For practical applications to radiation damage it is important to know how

DEA processes are modified in condensed-matter environments. To answer this

question, we use two approaches:

first, we investigate effects of clusterization, in particular how the DEA

process is affected if the attaching molecule is placed in a water cluster environment

[4]. Second, we study how the DEA rate is affected if the molecule is placed on a

surface. The condensed-matter effects can lead to a strong enhancement of the

attachment rates, but, on the other hand, they suppress vibrational Feshbach

resonance effects [5].

This work was done in collaboration with P. D. Burrow and G. A. Gallup

(UNL), V. Vizcaino and S. Denifl (University of Innsbruck), and J. Gorfinkiel (The

Open University, UK), and supporteed by the US National Science Foundation.

ABSTRACTS

11

REFERENCES [1] G. A. GALLUP, P. D. BURROW, I. I. FABRIKANT, PHYS. REV. A 79, 042701 (2009). [2] G. A. GALLUP AND I. I. FABRIKANT, PHYS. REV. A 83, 012706 (2011). [3] V. VIZCAINO, B. PUSCHNIGG, S. E. HUBER, M. PROBST, I. I. FABRIKANT, G. A. GALLUP, E.

ILLENBERGER, P. SCHEIER, S. DENIFL, NEW J. PHYS. 14, 043017 (2012). [4] I. I. FABRIKANT, S. CAPRASECCA, G. A. GALLUP, J. D. GORFINKIEL, J. CHEM. PHYS.136, 184301

(2012). [5] I. I. FABRIKANT, J. PHYS. B 44, 225202 (2011).

ABSTRACTS

12

Simplified Model to Describe the Dissociative Recombination of Polyatomic Ions of

Astrophysical Interest

S. Fonseca dos Santos1, N. Douguet1, V. Kokoouline2, A. E. Orel1

1Department of Chemical Engineering and Materials Science, University of California at Davis, Davis, CA 2Department of Physics, University of Central Florida, Orlando, FL 32816

We present theoretical results on the dissociative recombination (DR) of

many polyatomic ions H3+, CH3

+, H30+, HCNH+, NH4+, HCO+ and N2H+

. Besides their

astrophysical importance, they also share the characteristic that at low electronic

impact energies their DR process happens via the indirect DR mechanism. Applying

a general simplified model based on multichannel quantum defect theory that

accounts for all the main ingredients of indirect DR we calculated cross sections and

DR rates for these ions. Our results, as illustrated in Figs. 1 and 2, are in good

agreement with available experimental data.

Fig.1 – DR cross section of N2H+

Experimental data digitalized from

Geppert et al., Astrophys J 609, 459

(2004)

Fig.2 – DR cross section of H3+ Comparison between

experiments (CRYRING and TSR) and different levels

of theory of our group: a complete treatment (Fonseca

dos Santos et. al.) and the simplified model (Douguet

et.al.).

This work is supported by the DOE Office of Basic Energy Science and the National Science

Foundation, Grant No's PHY-08-55092 and PHY-08-55622 and NSF Grant No. PHY-08-55092.

ABSTRACTS

13

Theoretical Studies of Dissociative Recombination

Steven L. Guberman

Institute for Scientific Research

A long term aim of dissociative recombination research has been to find

agreement between theoretical and experimental total cross sections to at least

better than 20%. This goal has remained elusive and has not been achieved at low

electron energies for any molecular ion, including the simplest, H+2. Both theory and

experiment have made robust contributions to this disagreement. In this talk, I will

discuss recent theoretical calculations of dissociative recombination cross sections

for N+2. I will not show high resolution agreement with experiment because there are

no high resolution experimental cross sections for N+2 . However, I will show that

one must include minor dissociative channels [Guberman, 2012] if one is to obtain

agreement with a future experimental N+2. cross section which has a well

characterized ion electronic and vibrational population. An early storage ring

experiment [Peterson et al., 1998], restricted to “zero” electron energy, found that

the dissociative recombination rate constants for the lowest three ion vibrational

levels are quite similar in magnitude. The theoretical results agree with experiment

at low electron temperature but the theory finds that above room temperature, the

rate constant for v = 0 departs significantly from those for v > 0. The results are

important for ionospheric models at Earth [Fox and Dalgarno, 1985] and Mars [Fox

and Dalgarno, 1983; Fox and Hać, 1997] where the electron temperature is above

300 K and considerable N+2. vibrational excitation is present. Lastly, in a recent

storage ring experiment (Vigren et al., 2012) on HN+2. , an incorrectly derived rate

constant was attributed to contamination of the ion beam with 15N14N+. Did they get

it right?

ABSTRACTS

14

REFERENCES FOX, J. L. AND A. DALGARNO, J. GEOPHYS. RES. 88, 9027 (1983) FOX, J. L. AND A. DALGARNO, J. GEOPHYS. RES. 90, 7557 (1985) FOX, J. L. AND A. HAĆ, J. GEOPHYS. RES. 102, NO. E4, 9191 (1997). GUBERMAN, S. L., J. CHEM. PHYS. 137, 074309 (2012). PETERSEN, J. R., A. LE PADELLEC, H. DANARED, G. H. DUNN, M. LARSSON, Ǻ. LARSON, R. PEVERALL, C. STRÖMHOLM, S. ROSÉN, M. AF UGGLAS AND W. J. VAN DER ZANDE, J. CHEM. PHYS. 108, 1978 (1998). VIGREN, E., V. ZHAUNERCHYK, M. HAMBERG, M. KAMINSKA, J. SEMANIAK, M. AF UGGLAS, M. LARSSON, R. D. THOMAS AND W. D. GEPPERT, AP. J. 757, 34 (2012)

ABSTRACTS

15

Successes and Challenges of Frame Transformation Theory

Chris H. Greene

Purdue University, West Lafayette, IN 47907

This talk will give an overview of frame transformation theory, emphasizing

its application to electron-molecule collisions and especially the coupling between

electronic degrees of freedom with molecular rotation, vibration, and dissociation.

While the theory has had numerous successes, there remain problem areas that are

ripe for improvement and further development. Headway in strengthening ab initio

theoretical treatments of the electronic continuum states of molecules could be

decisive for making progress in this area.

ABSTRACTS

16

The R-Matrix Method for Attosecond Spectroscopy

A. G. Harvey, F. Morales, O. Smirnova

Max-Born-Institut, Max-Born Straße 2A, D-12489 Berlin, Germany

The advent of new XUV light sources such as free electron lasers, and the

development of high harmonic emission both as a light source and as a direct probe,

coupled with advances in detector technology and the laser alignment of molecules,

has opened up the possibility of observation, initiation and control of the fastest

molecular processes. Exposing aligned molecules to these short, femtosecond to

sub-femtosecond pulses leads to ionisation, and the angular distribution of ejected

electrons encodes information about the parent molecule [1,2]. High harmonic

emission from molecules can also encode information abou molecular structure and

dynamics [3,4].

The theoretical descriptions of both of these types of experiment need high

quality dipole matrix elements. They are used to calculate molecular frame

photoelectron angular distributions and in the recombination step of current,

sophisticated, models of HHG [5]. With this in mind we have converted the UK R-

matrix scattering codes [6,7] to treat photoionisation (or recombination) from

aligned molecules.

The molecular R-matrix method is a powerful, multichannel, ab initio

technique for treating electron-molecule interactions. It works by dividing the

configuration space of the molecule into an inner and outer region and making

different levels of approximation in each. The inner region rigorously takes into

account electron-electron effects such as exchange, correlation and polarisation and

in the outer region the electron moves in the long range, multipole potential of the

parent molecule. Matching to known asymptotic boundary conditions gives the

wavefunction representing the ionised molecule plus continuum electron.

Transition dipole matrix elements between this wavefunction and the inital bound

state of the molecule are produced, from which the desired photoionisation

observables may be obtained.

ABSTRACTS

17

We present the first application of our codes and compare with new

experimental data for the CO2 molecule [8,9].

REFERENCES [1] FOR A RECENT REVIEW SEE K. L. RAID, MOLECULAR PHYSICS, 3, 131, (2012).

[2] A. ROUZEE, ET AL., J. PHYS. B, 45, 074016, (2011).

[3] O. SMIRNOVA, ET AL., NATURE 460, 972–977, (2009).

[4] S. HAESSLER, ET AL., NATURE PHYSICS 6, 200 - 206, (2010) .

[5] SEE E.G. A. T. LE, ET AL., PHYS. REV. A 80, 013401, (2009).

[6] J.M. CARR, ET AL., EURO. J. PHYS. D, 66, 58 (2012).

[7] A. G. HARVEY AND J. TENNYSON, IN QUANTUM DYNAMIC IMAGING, A.D. BANDRUK AND M. IVANOV

(EDS.), SPRINGER 55-70 (2011).

[8] H. RUF, R. CIREASA, C. HANDSCHIN, V. BLANCHET, B. FABRE, S. WEBER, D. DESCAMPS, S. PETIT

F. MORALES, A. HARVEY, M. RICHTER, M. IVANOV, O. SMIRNOVA, Y. MAIRESSE (TO BE PUBLISHED).

[9] A. ROUZÉE, A. G. HARVEY, F. KELKENSBERG, W. SIU, G. GADEMANN, O. SMIRNOVA, M. J. J. VRAKKING

(TO BE PUBLISHED).

ABSTRACTS

18

Angular Dependence of Dissociative Electron Attachment to Methanol

Daniel J. Haxton

Lawrence Berkeley National Lab

I will show calculations on the angular dependence of dissociative electron

attachment to methanol, via the lowest, ~6eV A’’ resonance, obtained through fixed

nuclei calculations using the complex Kohn method. I do not consider the dynamics

after attachment and instead use the fixed nuclei attachment probabilities, averaged

over vibrational modes, to obtain the angular dependence prediction as a function of

recoil angles. These calculations are compared with the experiment of Adaniya,

Slaughter, Belkacem et al. at LBNL. The agreement between experiment and theory

is not excellent, but does indicate that the recoil angle of the hydrogen is most likely

about 15 degrees from axial, on average.

ABSTRACTS

19

Dissociative Recombination and Electron Attachment in the Interstellar Medium

Eric Herbst

Departments of Chemistry and Astronomy, University of Virginia Charlottesville, VA 22904, USA

Dissociative recombination and electron attachment are important

processes in the dense interstellar medium, especially in cold regions, where the

gas-phase chemistry is known to be dominated by ionic processes, and star

formation has not yet heated up the gas and dust. Observations from the far-

infrared satellite Herschel towards the star-forming region known as Orion KL

indicate, however, that dissociative recombination plays a key role even in warm

regions. In the hot outflow source in front of Orion KL, the unusual ions OH+ and

H2O+ are both present in high abundance despite the fact that they react with

molecular hydrogen, the most abundant species in the gas. On the other hand the

saturated ion H3O+ is not detected. To understand this unusual phenomenon, a

model with a very high rate of ionization caused mainly by far ultra-violet radiation

is advocated in which dissociative recombination competes with hydrogenation.

Observations from the ground show that molecular anions are present in a number

of different cold and “lukewarm” dense sources, where most of them are likely

formed via two-body radiative attachment, a process that is virtually unstudied both

theoretically and experimentally. With a simple phase-space theory for the process,

we and others have been able to reproduce most but not all of the observations of

molecular anions. More detailed studies of radiative attachment are clearly

required. Finally, the ortho-to-para ratio of assorted gas-phase species in the

interstellar medium is often difficult to understand. Here we consider the case of

the water cation, H2O+, where the measured ortho-to-para ratio in diffuse clouds

along the line of sight toward our galactic center is 4.8. The various processes

involved in determining this ratio are explored.

ABSTRACTS

20

Theoretical Methods for Treating Stable Anions for Which the Excess Electron Does Not Bind in the

Hartree-Fock Approximation

K. D. Jordan and V. Voora

Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260

Molecular anions can exist either as bound states (energy of the anion below

that of the ground state of the neutral) or as resonances (metastable states

embedded in the electron scattering continuum). One of the challenges to theory is

the characterization of those stable anions which, although bound, fail to bind in the

Hartree-Fock approximation. As a consequence, traditional quantum chemistry

methods such as MP2 and CCSD(T) are not applicable to these systems. We examine

two systems of this nature, water clusters with cavity-bound anions and C60, which

possesses a polarization bound s-type anion state. For the model water clusters, we

find that the ADC(2), EOM-MP2, and EOM-CCSD many-body methods all give similar

electron-binding energies. We also show that the orbital-optimized MP2 (OO-MP2)

method succeeds in binding the excess electron in these systems which

demonstrates that it is the orbital relaxation in response to low-order correlation

effects rather than high-order correlation effects that is the key to the electron

binding. We then turn our attention to C60 where we use the EOM-MP2 and EOM-

CCSD methods to demonstrate that it has an s-type polarization bound anion, with

about 10% of the electron density inside the cage and 90% outside.

ABSTRACTS

21

Analytic Three-Channel Model for Resonance-Averaged Direct and Indirect Dissociative

Recombination Processes of Molecular Ions

I. F. Schneider1, N. Pop2, and Ch. Jungen3

1 Laboratoire Ondes et Milieux Complexes UMR-6294 CNRS et Université du Havre, 25, rue Philippe Lebon, BP 540, 76058, Le Havre, France

2 Department of Physical Foundations of Engineering Polytechnical University of Timisoara RO-300223, Timisoara, Romania

3 Laboratoire Aimé Cotton du CNRS, Bâtiment 505 Université de Paris-Sud, F-91405 Orsay, France

An analytic three-channel model is developed for the description of

simultaneous direct and indirect dissociative recombination (DR) cross sections of

molecular ions with electrons. The model is for- mulated in terms of three

parameters describing the interactions between the electron-ion entrance channel,

e, the dissociation channel, d, and an `active' quasibound molecular Rydberg

channel, a, and yields resonance-averaged cross sections for low incident electron

energies. The relative magnitudes of the parameters determine (i) the height of the

downward steps at the ion vibrational thresholds and (ii) the relative contributions

of the direct and indirect processes. The model is intended to serve for the empirical

analysis of observed DR cross sections, and in particular it allows the assessment of

the extent to which re-ionization of the capture complex competes with dissociation.

The model is applied to the DR of H+3. and HCO+.

ABSTRACTS

22

Radiative Electron Attachment to Molecules of

Astrophysical Interest. Benchmark Study of CN-

Kokoouline1, N. Douguet2, S. Fonseca dos Santos2, O. Dulieu3, M. Raoult3, A. E. Orel2

1Department of Physics, University of Central Florida, Orlando, Florida 32816

2Department of CHMS, University of California at Davis, Davis, CA 95616 3Laboratoire Aime Cotton, CNRS, Bat 505, Universite Paris 11, 91405 Orsay Cedex, France

We have developed a first-principles approach to study the process of

radiative electron attachment (REA) to linea molecules of astrophysical interest Mol

+e_→ Mol-+ ħ . (Mol - = CnH- -, CnN- ). The approach is based on accurate ab initio

calculations of electronic bound and continuum states of the negative ion. The

electronic continuum states are obtained with the complex-Kohn variational

method. The benchmark calculation for the formation of the simplest observed ion,

CN-, by REA has produced a low rate coefficient, 5x10 _17 cm3/s at 30 K. We will

present also a preliminary result for the C4H- formation by REA. For this molecule,

the REA rate coefficient is expected to be larger by about a factor of 10 due to a

larger transition dipole moment. This study suggests that the negative molecular

ions, recently observed in the interstellar medium, can hardly be formed by the

process of radiative electron attachment.

The figure to the left shows potential

energy curves of the only electronic state

of CN- and several electronic states of CN.

The shape of the curves of the CN and

CN- ground states is almost the same.

The transition dipole moments are

almost geometryindependent. Thus,

during the REA process, the vibrational

quantum number is approximately

conserved.

ABSTRACTS

23

The figure to the left shows the

transition dipole moments between the

electronic bound state of CN-- and partial-

wave components of the initial CN+e-

states (continuum states). The transition

dipole moments are calculated for the

CN-equilibrium distance, R=2.27ao

The figure to the left shows the REA rate coefficients for the process starting with the ground vibrational level and different initial rotational states j (j=0,1,2,3,15) of CN. For each initial rotational state, the resulting cross-section is summed over all possible final rovibrational states of CN- .

This work is supported by the DOE Office of Basic Energy Science and the National

Science Foundation, Grant No's PHY-08-55092 and PHY-08-55622.

ABSTRACTS

24

Dissociative Recombination Measurements at Ion Storage Rings: Achievements and Perspectives

Holger Kreckel

Max-Planck-Institute for Nuclear Physics (MPIK), Heidelberg, Germany

In the past two decades heavy-ion storage rings have become the work

horses for electron recombination measurements with atomic and molecular ions.

Modern storage ring facilities provide a clean, almost background-free experimental

test bench and in combination with a collinear cold electron beam device, they allow

for precise energy-resolved recombination rate coefficient measurements with

superior resolution.

For atomic ions, the recombination is often dominated by a resonant

process, where the free electron is captured into a discrete state, while exciting one

of the bound electrons (di-electronic recombination). For molecular ions, on the

other hand, the energy gain of the capture process can be transferred into internal

energy of the neutral molecule. This can either lead to a direct non-resonant

recombination into a dissociative state (direct dissociative recombination) or

proceed through intermediate states that eventually couple to a dissociative channel

(indirect dissociative recombination).

We will give some examples that demonstrate the potential of the storage

ring technique and then focus on the dissociative recombination of the triatomic

hydrogen ion H3+. Being the simplest polyatomic molecule and a key species in the

interstellar medium, H3+ has received a lot of attention and the DR rate coefficient of

H3+ has been a controversial topic for years. We will describe the recent efforts for a

detailed comparison between measurement and theory for this benchmark

molecular ion.

Finally, we will give a brief outlook outlining the potential for DR

measurements at the new Cryogenic Storage Ring (CSR) that is currently under

development at MPIK.

ABSTRACTS

25

Complex-Scaled Equation-of-Motion Coupled-Cluster Method with Single and Double

Substitutions for Autoionizing Excited States: Theory, Implementation, and Examples

Anna Krylov

Dept. of Chemistry, University of Southern California Los Angeles, CA 90089-0482

Theory and implementation of complex-scaled variant of equation-of-

motion coupled-cluster method for excitation energies with single and double

substitutions (EOM-EE-CCSD) will be presented. The complex-scaling formalism

extends the EOM- EE-CCSD model to resonance states, i.e., excited states that are

metastable with respect to electron ejection. The method is applied to Feshbach

resonances in two well-studied systems, He and H-, The dependence of the results

on one-electron basis set is quantified and analyzed. Energy decomposition and

wave function analysis reveals that the origin of the dependence is in electron

correlation, which is essential for the lifetime of Feshbach resonances. It is found

that one electron basis should be sufficiently flexible to describe radial and angular

electron correlation in a balanced fashion and at different values of the scaling

parameter, θ. Standard basis sets that are optimized for not-complex-scaled

calculations (θ=0) are not sufficiently flexible to describe the θ-dependence of the

wave functions even when heavily augmented by additional sets.

ABSTRACTS

26

Photoionization in the Molecular Frame

Robert R. Lucchese

Department of Chemistry, Texas A&M University College Station, TX 77843

There has been a resurgence of interest in molecular photoionization and

the corresponding electron-molecular ion scattering dynamics. This interest is in

large part prompted by the development of improved and new light sources which

enable the scattering dynamics to be probed in the molecular frame. A discussion

will be given of recent studies on single photon molecular frame photoelectron

angular distributions (MFPADs) and the related recoil-frame photoelectron angular

distributions (RFPADs), multiphoton RFPADs, high harmonic generation from

impulsively aligned molecules, photoionization of impulsively aligned molecules,

and rescattering spectroscopy. In each case, an understanding of the electron-

molecular ion scattering dynamics is an essential ingredient to understanding the

whole process.

ABSTRACTS

27

Molecular Anions in the Laboratory and in Space

Michael C. McCarthy

Harvard Smithsonian Center for Astrophysics, Cambridge, USA

The importance of negative ions (anions) in astronomy was demonstrated in

1939 by Rupert Wildt who showed that H¯ is the major source of optical opacity in

the solar atmosphere, and therefore the material which one mainly sees when

looking at the sun and similar stars. Despite the detection of many neutral and

positively-charged molecules in space in the intervening 70 years, it was not until

2007 that a molecular anion (C6H¯) was identified for the first time in two rich

astronomical sources on the basis of laboratory measurements of its rotational

spectrum. Since that initial discovery, the closely-related carbon-chain anions, CCH¯,

C4H¯, C8H¯, NCO¯, CN¯, and C3N¯ were subsequently detected in our laboratory; all but

two of them have now been detected in space, and there is strong evidence for C5N¯

there as well, even thought its rotational spectrum has not yet been measured in the

laboratory. The most readily observed anion, C6H¯, has now been detected in at

least six other astronomical sources, suggesting that anions are probably widely

distributed in the interstellar gas, often present at the level of at least of few percent

relative to the neutral parent. The high abundance of CN¯ relative to CN in the

circumstellar shell of the evolved carbon star IRC+10216, and the unexpected

spatial distribution of C6H¯ relative to C6H in this source suggest that formation

routes other than radiative electron attachment may be important.

ABSTRACTS

28

Low-­Energy Electron-­Molecule Collisions with the Schwinger Multichannel Method†

Vincent McKoy

California Institute of Technology Pasadena, California 91125

Collisions of low--‐energy electrons with polyatomic molecules are

important in many contexts, from the astrophysical to the biological. Modelers need

cross sections for a variety of processes, among them elastic scattering, dissociative

attachment, and vibrational and electronic excitation. However, both measurements

and calculations are difficult, and data remain scarce for even the most important

molecules, such as water. In this talk, I will review the formulation we have

developed for ab initio computation of electron--‐molecule collision cross sections,

describe its numerical implementation, and discuss features of the method that are

particularly advantageous for applications to general polyatomics, as well as the

method’s limitations. Recent applications to problems such as resonant collisions

with the constituents of DNA and electronic excitation of water illustrate the

method’s capabilities. In closing, I will comment on the challenges that remain and

the prospects for addressing them.

ABSTRACTS

29

Very Low-Energy Electron-Induced Damage of DNA

Thomas M. Orlando

School of Chemistry and Biochemistry and School of Physics Georgia Institute of Technology Atlanta, GA USA 30318

We have examined theoretically and experimentally the low energy (1-25

eV) electron-induced damage of DNA oligomers. Specifically, we have calculated the

elastic scattering of 5-30 eV electrons within the B-DNA 5'-CCGGCGCCGG-3' and A-

DNA 5'-CGCGAATTCGCG-3' sequences using the separable representation of a free-

space electron propagator and a curved wave multiple scattering formalism. The

disorder brought about by the surrounding water and helical base stacking leads to

featureless amplitude build-up of elastically scattered electrons on the sugars and

phosphate groups for all energies between 5-30 eV. However, some constructive

interference features arising from diffraction were revealed when examining the

structural waters within the major groove. These appear at 5-10, 12-18 and 22-28

eV for the B-DNA target and at 7-11, 12-18 and 18-25 eV for the A-DNA target.

Though the diffraction depends upon the base-pair sequence, the energy dependent

elastic scattering features are primarily associated with the structural water

molecules localized within 8-10 Å spheres surrounding the bases and/or the sugar-

phosphate backbone. The electron density build-up occurs in regions of electron

attachment resonances, direct electronic excitation and dissociative ionization. We

correlated these scattering features with our measured DNA single and double

strand breaks and suggested that states involving major groove waters may be

important in low-energy electron induced damage of DNA. Compound resonance

states involving interfacial water and excitation energies > 5 eV seem to be required

for lethal double strand breaks.

We have also recently extended this work to excitation energies below 5 eV

by examining the damage using Raman-microscopy and scanning electrostatic force

microscopy. Very efficient damage via single strand breaks is observed below 5 eV

excitation energies. This involves π* negative ion resonances that are initially

ABSTRACTS

30

localized on the bases but transferred to the σ* states of the sugar-phosphate bond.

The efficacies of these channels depend upon the base-pair sequences as well as the

presence of water.

ABSTRACTS

31

The Dynamics of Resonant Electron Collisions with Carbon Dioxide

T. N. Rescigno

Lawrence Berkeley National Laboratory

Despite the fact that the principal features of low-energy electron-CO2

collisions have been known and studied for over forty years, there are numerous

misconceptions and significant gaps in the extant literature on the subject. The

scattering is characterized by a rapid rise in the total cross section below 1 eV,

anomalous threshold behavior for excitation of symmetric stretch and bending

vibrational modes, resonant vibrational excitation near 4 eV with weak

``boomerang'' structure in the excitation cross sections and dissociative electron

attachment cross sections leading to ground-state CO + O- which peak near 4 eV and

8 eV and have angular distributions which show large deviations from axial recoil.

The nuclear dynamics associated with all these features is intrinsically polyatomic

in nature and cannot be described with one-dimensional models. The goal of our

current work is to provide a consistent description of all these phenomena and to

resolve a number long-standing paradoxes concerning the dissociation dynamics.

ABSTRACTS

32

Complex Generalized Hartree-Fock

Eric J. Sundstrom1, David Small1, and Martin Head-Gordon1,2

1Department of Chemistry, University of California, Berkeley, California 94720

2Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, 94720

Since the early days of quantum chemistry there has been a great deal of

discussion regarding symmetry breaking of Hartree-Fock (mean-field) wave

functions including a full group theoretical classification of these solutions.[1]

Despite the considerable discourse on this topic, due to computational concerns,

many of these broken symmetry methods (other than simple unrestriction) were

never thoroughly studied within the quantum chemistry community. Recently,

completely broken symmetry wave functions have come back into vogue and there

are many groups working with methods related to these wave functions.[2]

Here we present a fundamental study assessing for which classes of

molecular systems utilizing generalized spin and complex broken symmetry wave

functions may provide more accurate potential energy surfaces. We calculate the

eigenvalues of the Hessian which when negative indicate instability of these wave

functions; this allows us to identify saddle points and locate legitimate local minima.

Exploiting the blocked nature of the Hessian allows us to resolve internal

(symmetry retaining) and external (symmetry breaking) degrees of freedom.[3] We

also compute various spin observables to ascertain the equivalence of these solution

which may become important when using the wave functions with correlation

methods.

REFERENCES [1] HIDEO FUKUTOME, INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY 20(5), PP. 955–

1065 (1981). [2] GUSTAVO E SCUSERIA, CARLOS A JIMÉNEZ-HOYOS, THOMAS M HENDERSON, KOUSIK

SAMANTA, AND JASON K ELLIS, THE JOURNAL OF CHEMICAL PHYSICS 135(12), PP. 124108 (2011). [3] ROLF SEEGER AND JOHN A POPLE, THE JOURNAL OF CHEMICAL PHYSICS 66(7), PP.3045–3050

(1977).

ABSTRACTS

33

R-matrix and Vibrational Frame Transformation in Studies of Molecular Photodetachment

Michal Tarana1, 2 and Chris H. Greene1

1Department of Physics, Purdue University, 525 Northwestern Avenue, West Lafayette, Indiana 47907-2036, USA

2JILA, University of Colorado, Boulder, Colorado 80309-0440, USA

The state of the art in the theoretical treatment of the electron interactions with

small molecules can be topically divided into the ab initio scattering calculations in the fixed-

nuclei approximation based on the methods of quantum chemistry and the scattering

calculations that incorporate nuclear dynamics. Both types of methods have their own set of

issues and are subject of the theoretical research. As to the first subject, the ab initio

molecular R-matrix is a well developed tool that uses molecular electronic structure theory

for calculations of the elastic and electronically inelastic scattering matrices [1]. First, several

aspects of the ab initio R-matrix method will be discussed. The study of the 2Πg continuum

and bound states of O2- in the fixed-nuclei approximation will be presented. Various models

of neutral O2 will be introduced and the question, how well the polarization and correlation

effects can be represented using rather limiting CAS CI approach, will be addressed. An

alternative method of calculation of the R-matrix from the Hamiltonian in the inner region

will be introduced and the test of its numerical performance will be presented. This method

is designed to handle large CAS models, where the usual complete diagonalization of the

Hamiltonian becomes numerically too demanding. It is based on solving the system of linear

equations individually for every scattering energy. The energy-dependent vibrational frame

transformation (VFT) will be discussed as a theoretical tool to study the vibrational

dynamics of the electron collisions with small neutral molecules and photodetachment of

molecular anions [2, 3]. The VFT study of the photodetachment of O2- will be presented in

terms of the photoelectron angular distributions calculated for different vibrational states.

Connection between the ab initio R-matrix calculations and the VFT will be discussed. This

work was supported in part by the Department of Energy, Office of Science.

REFERENCES [1] J. TENNYSON, PHYS. REP. 491, 29 (2010). [2] H. GAO AND C. H. GREENE, J. CHEM. PHYS. 91, 3988 (1989). [3] H. GAO AND C. H. GREENE, PHYS. REV. A 42, 6946 (1990).

ABSTRACTS

34

Bound and Continuum States in Electron – Molecule Collisions Using the R-Matrix Method

Jonathan Tennyson

Physics & Astronomy, University College London, London WC1E 6BT, UK

Use of the R-matrix method to treat the electron-molecule collision problem

has recently been reviewed [1]. Recent work has focused on improving the

description and range of validity of the scattering problem by the use of

pseudostates, detailed calculations of bound and continuum states with a focus on

the avoided crossings and making the UK Molecular R-matrix code widely accessible

to non-experts [2]. This last task has particular importance for providing data for

models of technological plasmas and has led to the implementation of a number of

new procedures to aid this work.

The R-matrix with pseudostates method (RMPS) has been widely used in

atomic physics to extend collision calculations to the energies above the target

ionisation threshold [3]. The molecular RMPS method was originally developed to

allow for the ab initio treatment of electron impact ionisation [4]. However the

ability of the RMPS method to give a converged representation of polarisation [5]

has meant that it has become the method of choice for treating problems where

polarisation effects are important.

RMPS studies of electron collisions with C__2 anions showed that the observed

di anionic resonances are due to strong polarisation effects which overcome the

Coulomb repulsion between the two extra electrons [7]. The method was also able

to recover the background electron-impact detachment cross section due to high

impact parameter collisions which could be represented by high-ℓ transitions to

pseudo-states using the dipole Born approximation. This method has also been

successfully applied to positron –molecule collisions [8]

The RMPS method is computationally expensive and has driven the

development of algorithms which obviate the need to explicitly obtain all the

ABSTRACTS

35

eigenvectors of the inner region Hamiltonian [9]. The largest calculation attempted

so far obtaining 5000 eigenvalues for a 650 000 dimensional matrix [8]. Work on

improved parallel procedures to further extend the scope of RMPS calculations is in

progress. Electron collision calculations are important for characterizing resonances

which, for molecular ions, occur in infinite series. Such calculations can be extended

to negative scattering energies giving results also on infinite bound-state Rydberg

series and, which is of particular importance for studies of dissociative

recombination, how these states interact with dissociative resonance states Results

of a detailed study on the nitrogen molecule will be presented.

REFERENCES 1. J. TENNYSON 2010 PHYS. REP. 491 29 2. J. TENNYSON ET AL 2007 J. PHYS. CONF. SERIES, 86, 012001 3. K BARTSCHAT 1998 COMPUT. PHYS. COMM. 114 168 4. J.D. GORFINKIEL AND J. TENNYSON 2004 J. PHYS. B: AT. MOL. OPT. PHYS. 37 L343; 2005 IBI

38 1607 5. M JONES AND J. TENNYSON 2010 J. PHYS. B: AT. MOL. OPT. PHYS. 43 045101 6. G. HALMOVA AND J. TENNYSON 2008 PHYS. REV. LETT. 100 213202 G. HALMOVA ET AL 2008 J.

PHYS. B: AT. MOL. OPT. PHYS. 41 155201 7. R. ZHANG ET AL 2011 J. PHYS. B: AT. MOL. OPT. PHYS. 44 035203; IBID 44, 195203 (2011). 8. J. TENNYSON 2005 J. PHYS. B: AT. MOL. OPT. PHYS. 37 1061

ABSTRACTS

36

DESIREE: A Unique Cryogenic Electrostatic Storage Ring for Merged Ion-Beams Studies

R. D. Thomas

Department of Physics, Stockholm University, SE-106 91 Stockholm, Sweden

In this presentation I will describe the design and construction of a novel

type of ion storage device currently undergoing commissioning at Stockholm

University, Sweden. This device uses purely electrostatic focusing and deflection

elements and allows ion beams of opposite charge to be confined under extreme

high vacuum and cryogenic conditions in separate “rings” and then merged over a

common straight section. The unique construction of this Double ElectroStatic Ion

Ring ExpEriment (DESIREE) apparatus allows for studies of interactions between

cations and anions at low and well-defined centre-of-mass energies down to 10 meV

as was achieved in magnetic storage rings between ions and electrons (see e.g. ref.

1). The heart of DESIREE is shown schematically in Fig. 1.

Figure 1: A schematic of DESIREE’s heart: the cooled rings and merging region.

ABSTRACTS

37

The technical advantages of using purely electrostatic over magnetic

elements are many, but the most relevant are: electrostatic elements are more

compact and easier to construct; remanent fields, hysteresis and eddy-currents,

highly problematic in magnetic devices, are no longer relevant, and for low energy

ion beams (keV vs MeV) electrostatic elements are more efficient to use. I will

present the current state of the DESIREE facility: the system is now under vacuum at

cryogenic temperatures & results from the first injection show storage of low

energy ions up to 30 minutes, and highlight some of the technical issues that have

arisen during its development and construction [2].

Finally, the advantages of this design are a boon to fundamental

experimental studies, not only in atomic and molecular physics but also in the

boundaries of these fields with chemistry and biology, and I will finish by discussing

several examples of such potential research.

REFERENCES [1] R. D. THOMAS, MASS SPECTROM. REV., 77, 485 (2008) [1] R. D. THOMAS ET AL., REV. SCI. INSTRUM. 82, 065112 (2011)

 

DIRECTIONS

TAXI  CABS  

If  you  need  to  take  a  taxi,  there  is  a  taxi  stand  in  Harvard  Square  directly  across  the    street  from  the  subway  station.  In  the  unlikely  event  that  there  are  no  cabs  available  at  the  stand  here  are  two  local  phone  numbers.    Ambassador:  1-­‐617-­‐492-­‐1100  Yellow:    1-­‐617-­‐547-­‐3000  

 

IF  YOU  ARE  WALKING:  

ITAMP  is  located  at  the  Harvard-­‐Smithsonian  Center  for  Astrophysics  located  at  60  Garden  Street,  Cambridge  Ma  (marked  with  the  red  arrow  above)  and  is  a  20  min  walk  from  Harvard  Square  subway  station.  

From  the  T,  walk  down  Massachusetts  Ave  until  it  intersects  with  Garden  Street.  Continue  down  Garden  Street  until  you  come  to  a  set  of  lights  at  Linnean  St.  and  Garden  St.  Linnean  will  be  on  your  right  The  “driveway”  looking  road  directly  across  from  Linnaean  Street  is  the  60  Garden  St.    

 The  easiest  way  to  get  to  Phillips  Auditorium  is  to  continue  up  the  driveway  away  from  Garden  Street.    You  will  pass  the  tennis  courts,  a  sports  facility  on  your  left  and  another  grey  building.  Continue  up  the  incline  until  you  come  to  the  brick  building  on  your  left.  Walk  to  the  end  of  the  red  brick  building  on  your  left,  turn  left.  You  will  see  stairs  that  lead  to  the  white  doors  of  the  Auditorium  directly  in  front  of  you.  This  is  Phillips  Auditorium