A3: DESIREE
-
Upload
kane-hebert -
Category
Documents
-
view
51 -
download
1
description
Transcript of A3: DESIREE
A3: DESIREE
Designand examples of planned experiments
Belfast, July 1, 2003
Henning Schmidt, Stockholm University
(Double ElectroStatic Ion Ring ExpEriment)
Stockholm Low-Energy facilities:
DESIREEDouble ElectroStatic Ion Ring ExpEriment.
CRYSIS (EBIS source for very high charge states e.g. U70+)
ECR ion source for intense beams of moderately high charge states.
Outline
The DESIREE project Motivation: Mutual Neutralization Brief technical description Planned experiments
AMO Physics• Example: Diffuse interstellar absorption
bandsBiomolecules
• Example: ‘Electron Capture Dissociation’
Summary
Plasma environments:Plasma environments:The degree of ionization is a The degree of ionization is a
determining factor for the ongoing determining factor for the ongoing chemistry. chemistry. Processes that affect this parameter Processes that affect this parameter are therefore crucial.are therefore crucial.
Electron-Ion recombination:Electron-Ion recombination: XX+ + + e+ e- - X + h X + h (atomic recombination) (atomic recombination)
ABAB+ + + e+ e- - A + B (dissociative A + B (dissociative recombination)recombination)
Mutual Neutralization :Mutual Neutralization : XX++ + Y + Y-- X + Y X + Y
AA-- + BC + BC++ A + BC or A + B + C A + BC or A + B + C
DESIREEDESIREEDDouble ouble EElectro-lectro-SStatic tatic IIon on RRing ing EExpxpEErimentriment
1 m
Double-walled vacuum vesselDouble-walled vacuum vessel Outer tank 300K - Inner tank 15KOuter tank 300K - Inner tank 15K Cooling by cryogeneratorsCooling by cryogenerators
Expected vacuum in inner Expected vacuum in inner partpart 300 K: <10300 K: <10-11-11 mbar mbar 15 K: Density reduced by order(s) 15 K: Density reduced by order(s)
of magnitudeof magnitude
Ion sources:Plasma Ion SourcesSputter Source (Negative Ions)ESI Source (Biomolecules)ECRIS (Highly Charged Ions)
1 m
Position-sensitive detector
ELISA
DESIREE
Merged-beams experiments
Longitudinally: Kinematical compression Transversely: Ion optics determines: < 1 eV seems feasible. Can beam cooling be developed?
Relative velocity definition:
Example: MN H-+H2+
E=10 keV/amu, Erel=1 eV, Amax=1 cm2,=1.6.10-14cm2 (COB), I+=I-=100 nA, L=80 cm: 44 s-1
Background rate is similar - The key point is that in MN there are (at least) two neutrals in coincidence!!
How about experiments with Biomolecules?
Count Rate estimates:
RN: In above example N=4.106. Feasible for ESI with trap
Three special features of DESIREE:
Double-ring structure: Merged beams positive/negative ion collisions.
Cryogenic system: Extremely good vacuum Long storage
lifetime. Internally cold molecular ions.
Electrostatic confinement: High mass-to-charge ratios (i.e. Biomolecules). Absence of magnetic-field mixing in lifetime
measurements
Examples of proposed experiments at the DESIREE facility:
Atoms and ‘Small’ Molecules: Single-Ring Experiments
Lifetime measurements of metastable ions (He-, C60q+,…)
LASER spectroscopy of atomic/molecular ions (e.g. Cn-)
Merged-Beams ExperimentsMutual Neutralization Collisions
• Fundamental systems (e.g. H-+H2+ …..)
• Astrophysical plasmas (e.g. Cn-+H3
+, H3O+,….)
• Atmospherical ion chemistry.
Collisions involving fullerenes(C60
q++C60-, Ar8++C60
-,….)
Biomolecules: Single-Ring Experiments (already pursued at ELISA)
Lifetime and stability(J.U.Andersen et al, to be published)
LASER spectroscopy(e.g. GFP: S.B.Nielsen et al PRL 87, 228102 (2001))
Merged-Beams ExperimentsElectron Capture Dissociation in Negative/Positive ion
collisionsCoulombic explosions induced by highly charged ions
Biomolecules:
Examples of proposed experiments at the DESIREE facility:
Biomolecules: Single-Ring Experiments (already pursued at
ELISA)Lifetime and stability
(J.U.Andersen et al, to be published)LASER spectroscopy
(e.g. GFP: S.B.Nielsen et al PRL 87, 228102 (2001))
Electron Capture Dissociation
ECD is important in protein sequencing because it breaks other bonds than those accessed in collision-induced dissociation.
ECD is studied by introducing electrons in the plasma of FT-ICR mass spectrometer. No control of electron impact energy.
Using simple negative ion to carry the electron, low (even below zero) and well-controlled relative energy is obtained.
Electron-transfer
10 a0
10 a0
Area of impact for ’distant’ collisions.
Experimental indication of distant collision: Detection of neutral
at proper time in relation to the arrival of the biomolecule(ar fragments)
Summary:
DESIREE can be built!We can do new AMO physics in single-ring
and particularly in merged-beams configuration (Mutual Neutralization)
Spectroscopy and lifetime measurements for biomolecular ions - ELISA
’ECD’ like processes and HCI-biomolecular ion interaction in merged-beams - DESIREE unique
The End!
DESIREE People:
Primary investigator: Ö. SkeppstedtDesign group:
K-G Rensfelt, M. Andersson, L. Bagge,H. Danared, J. Jensen, L. Liljeby, H.T. Schmidt, K. Schmidt, A. Simonsson
Contributors to the Scientific Programme:H. T. Schmidt, H. Cederquist, T. Hansson,J. Jensen, M. Larsson, S. Mannervik,P. vd Meulen, J. Pettersson. P. Royen,E. Uggerud, R. A. Zubarev
New Leif?New Life!