Interrogating hydrocarbon radicals Interrogating hydrocarbon radicals

Timothy SchmidtTimothy SchmidtUniversity of SydneyUniversity of Sydney

New South Wales, AustraliaNew South Wales, Australia

Basel, Switzerland. 2001-2003

Maier Group

Where is Basel?

Here

More specifically…

Basel

The locals…

Interstellar carbon

Sun’s carbon abundance : 370 C atoms per 106 H atoms

Recommended galactic value : 225±50 C atoms per 106 H atoms

In the lines of sight towards many stars, carbon is depleted:

Sco – 26-126 C atoms per 106 H atoms

Oph – 41-141 C per 106 H atoms

…available for molecules and dust grains!(Dude, where’s my carbon)? htt

p://

ww

w.n

e.jp

/asa

hi/s

tella

r/sc

enes

/obj

ect/

zeta

_oph

.jpg

ISM – Diffuse interstellar bands, DIBs (optical)

Dense clouds and nebulae – Unidentified infrared bands, UIRs (3.3 mm, 6.7 mm)

Comets – small molecules

Red Rectangle – extended red emission and Red Rectangle Bands (optical)2005 FA13MOLECULAR EMISSION STRUCTURE IN THE RED RECTANGLE - SEQUENCE BANDS?

Looking for the carbon

Properties of the DIBs

appropriated from Ben McCall (www)

Series of absorption features between about 400 nm and 900 nm (+ a few more)Thought to be due to carbonaceous molecules (cations probable)

Carbon chains and polycyclic aromatic hydrocarbons among leading candidates

DIBs Hobbs et al a catalog of diffuse interstellar bands in the

spectrum of HD 20482710% of light missingat this wavelength

due to gas phase molecules… what are they?

Carbon Chains

HC2nH HC2n+1HLargest identified interstellar molecules are carbon chains.Oscillator strengths can be huge… less material required.

x xy y

Electrical Discharge Source

HV

HCCH

HCCH

HCCCCCCCCCCCH

HCCCCCCCCCCCCCCCH

C 6Hn

C 9HnC 8H

n C 10H

nC 11

Hn

C 12H

nC 13

Hn

C 14H

nC 15

Hn

C 16H

nC 17

Hn

13

Detector

Source

Extractionof ions

TOF MS

Resonance 2-Colour 2-Photon Ionization (R2C2PI)

Ionization continuum

+e-

Chamber in Sydney

HC2nH B1u+ ← X1g

+

Pino et al., JCP 114, 2208

HC2nH A1u/u- ← X1g

+

HC2nH A1u/u- ← X1g

+

Ding et al., PCCP 5, 4772 (2003)

HC2n+1H A3u- ← X3g

-

B ← X transitions carry theoscillator strength

+

±

HOMO

SOMO

LUMO

No matches to DIBs for carbon chains

HCC

CCCC

CH

HCC

CCCC

CCCH

HCC

CCCC

CCCC

CH

HCC

CCCC

CCCC

CCCH

HCC

CCCC

CCCC

CCCC

CH

HCC

CCCC

CCCC

CCCC

CCH

HCC

CCCC

S

HCC

CCS

HCC

CCCC

CCS

HCC

CCCC

CCCC

S

Longer chains must be measured

HC19H in UV, HC26H in UV

C2n+1H3H

-C☰C-C ☰

C-

H|C-C☰C-C ☰ C-H

H-C☰

C-C ☰

C-C-C ☰ C-H

H-C☰C-C ☰

C-

H-C

☰C-

C ☰

C-C-C ☰ C-C ☰ C-HH-C☰C-C ☰ C-

Some more new molecules

CH3CCCCCCCH

HCCCCCCCH

Some more new molecules

H-C☰C-C ☰ C-

H|C-C☰C-C ☰ C-H

H-C☰

C-C

☰ C

-CH 3

|C-C☰C-C ☰ C-H

Still no match to DIBs

H-C☰C-C ☰ C-

H|

C -C☰C-C ☰

C-H

HCC

CCCC

CH

HCC

CCCC

CCCH

HCC

CCCC

CCCC

CH

HCC

CCCC

CCCC

CCCH

HCC

CCCC

CCCC

CCCC

CH

HCC

CCCC

CCCC

CCCC

CCH

HCC

CCCC

S

HCC

CCS

HCC

CCCC

CCS

HCC

CCCC

CCCC

S

H-C☰

C-C

☰ C

-

CH 3

|C-C☰C-C ☰ C-H

H-C☰

C-C

☰ C

-C-C ☰

C-C

☰ C

-H

H-C☰C-C ☰ C-

H-C☰

C-C

☰ C

-C-C ☰ C-H

H-C☰C-C ☰

C-

CH3C

CCCC

CCH

2004 MJ132004 WA03

Sydney, Australia. 2004-2010

Laser spectroscopy supergroup 2009

DIB spectrum

RRB spectrum - fluorescence

Sarre et al., Science 269 (1995)

5799Å

Red Rectangle and DIBs

The “Unidentified Infrared Bands” - believed due to aromatic material in

Interstellar medium.

The Red Rectangle

Aromatic material?

Kwok

, Nature

430,

895

(200

4)

C2 Swan bands in Red Rectangle

Rob Sharp AAO

v=0

v=1v=2

v=0

v=1v=2

a3u

d3g

Swan system,Wollaston 1802

C6H6 discharge

Unidentified CRDS laboratory spectrum from Thaddeus/McCarthy labJet-cooled CRDS spectrum obtained in Basel

Can fluorescence spectroscopy help?

4429Å DIBHV

C6 H

6

C 6H 6

? ?

C6H6 discharge – laser induced fluorescence

C3?

?

??

?

?

Dr Neil James Reilly(sold to McCarthy)

Benzene discharge(normal fluorescence excitation spectrum)

C2

Not C2 !!

Fluorescence of a benzene discharge

Some electronic states of C2

v=0

v=1v=2

v=0

v=1v=2

a3u

d3g

v=0

v=1v=2

X1g+

v=0

v=1v=2

A1u

Swan system1802Phillips system

1948

v=0

v=1v=2

b3g-

Ballik-Ramsay system1958

v=0

v=1v=2

c3u+

d-c systemNot seen until 2006

c3u+ state of C2

g

g

u

u

g

Swan d-c

d-c system observed!

d-c system observed

2006 RC07; 2007 RD03

Named band systems

Kokkin-Reilly-Morris-Nakajima-Nauta-Kable-Schmidt?

Inspiration

Kokkin, Reilly, Morris, Nakajima, Nauta, Kable and Schmidt, JCP 231101 (2006)

Back to the C6H6 discharge..

C2

?

? ?

?

??

?

?

origin DF

C2C2

Dispersed fluorescence

C2

?

? ?

?

??

?

?

? = same molecule!

2DF spectrum of benzene discharge

C2

I2

C3

CH

2DF spectrum of CH

P-P

P-Q

P-RR-R

R-P

R-Q Q-Q

Q-R

Q-P

C3

476 nm

2DF spectrum of benzene discharge

Set detection window over molecule X

1000 cm-1 = ring breathe? = aromatic?

Single species spectrum

Measure the mass…

Damian Kokkin

Dr Damian Leigh Kokkin(sold to McCarthy)

Measure the mass…

S0

S1

1+1’ REMPI

Damian Kokkin

R2C2PI spectrum @ mass 115

mass (X) = 115

X = C9H7

LIF

R2C2PI m/z=115

Possible isomers of C9H7 (that are aromatic)

IP too high Maybe Maybe

Indenyl radical

1-phenylpropargyl3-phenylpropargyl

Some ground state frequencies (cm-1)

Experiment B3LYP/6-311G**×0.97

29 121 120

28 319 320

27 422 422

26 620 609

25 630 620

24 674 652

23 823 810

Resonance-stabilized radicals

3PPR

1PPR

+ CH4

+ CH4

1P1P + •CH3

3P1P + •CH3

H = 60kJ/mol

H = 100kJ/mol

Data from Prof. Leo Radom (USyd)

Hobbs et al a catalog of diffuse interstellar bands in the

spectrum of HD 204827

1PPR not a DIB carrier

1PPR also produced from 1-hexyne…

↓471nm↓462nm

this is not noise, it is fluorescence from multiple species

emis

sion

excitation

2dF…

dispersed fluorescence of a1

0 1000 2000 3000

most intense emission feature seen in 2d

trans 1-VP 3-VPsym Mode Exp. (cm⁻¹) Calculated (cm⁻¹)

a' 17 169 165 138a' 16 390 386 322a' 15 540 540 523a' 13 910 900 1010a' 12 1064 1067 1041a' 11 1127 1153 1247a' 10 1265 1261 1278a' 9 1304 1302 1400a' 7 1496 1504 1526a' 6 2024 2044 1985

171

161151

131

121

111 10171

6191 trans 1-vinylpropargyl

two conformers

=168 cm⁻¹

3463 cm⁻¹ 3634 cm⁻¹

(G3B3 level of theory)

0 1000 2000 3000

dispersed fluorescence of b1origin transition of cis 1-vinylpropargyl

cis 1-VP 3-VPsym Mode Exp. (cm⁻¹) Calculated (cm⁻¹)

a' 17 155 153 138a' 16 373 373 322a' 15 642 620 523a' 13 932 914 1010a' 12 1019 1011 1041a' 11 1111 1122 1247a' 10 1217 1223 1278a' 9 1396 1371 1400a' 7 1503 1508 1526a' 6 2032 2058 1985

171 161 151 131

121

111

101

91

71

61

also not DIB carrierHobbs et al a catalog of

diffuse interstellar bands in the spectrum of HD 204827

not DIB carrierHobbs et al a catalog of

diffuse interstellar bands in the spectrum of HD 204827

Of course, no match to DIBs

H-C☰C-C ☰ C-

H|

C -C☰C-C ☰

C-H

HCC

CCCC

CH

HCC

CCCC

CCCH

HCC

CCCC

CCCC

CH

HCC

CCCC

CCCC

CCCH

HCC

CCCC

CCCC

CCCC

CH

HCC

CCCC

CCCC

CCCC

CCH

HCC

CCCC

S

HCC

CCS

HCC

CCCC

CCS

HCC

CCCC

CCCC

S

H-C☰

C-C

☰ C

-

CH 3

|C-C☰C-C ☰ C-H

H-C☰

C-C

☰ C

-C-C ☰

C-C

☰ C

-H

H-C☰C-C ☰ C-

H-C☰

C-C

☰ C

-C-C ☰ C-H

H-C☰C-C ☰

C-

CH3C

CCCC

CCH

2006 WH07 (not) IDENTIFYING FLUORESCENT HYDROCARBON RADICALS FROM A BENZENE DISCHARGE.

Resonance-Stabilized Hydrocarbon Radicals

Resonance-Stabilized CnHm Radicals

?-H

Indene adds H barrierlessly to afford the 1-indanyl radical

+H

Indanyl radicals

2009 TJ09

Free to a good home in 2011

2010 WG09 - Chalyavi

Red rectanglenebula

1-naphthylmethyl

Hexabenzocoronene, C42H18

D6h Symmetry– Forbidden Origin

B2u A1g

– Modes induced by e2g vibrations

a and b false origins

f = 1.4 x 10-3

Upper limit of 4x1012cm-2

2x10-4 fraction of carbon

Benzene-like orbitals

HOMOs

LUMOs

Is the transition B2u – A1g, like benzene?

A D3h jewel

00

0

E”

A2”

Jahn-Teller…

Herzberg-Teller?

Jahn-Herzberg-Teller2 ?

(sigh)

H-C☰C-C ☰ C-

H|

C -C☰C-C ☰

C-H

HCC

CCCC

CH

HCC

CCCC

CCCH

HCC

CCCC

CCCC

CH

HCC

CCCC

CCCC

CCCH

HCC

CCCC

CCCC

CCCC

CH

HCC

CCCC

CCCC

CCCC

CCH

HCC

CCCC

S

HCC

CCS

HCC

CCCC

CCS

HCC

CCCC

CCCC

S

H-C☰

C-C

☰ C

-

CH 3

|C-C☰C-C ☰ C-H

H-C☰

C-C

☰ C

-C-C ☰

C-C

☰ C

-H

H-C☰C-C ☰ C-H-

C☰C-

C ☰

C-C-C

☰ C-H

H-C☰C-C ☰ C-

CH3C

CCCC

CCH

Acknowledgmentsfrom Basel. 2001-2003

Prof. John P. MaierProf. John P. MaierDr Thomas PinoDr Thomas Pino

Dr Andrey BoguslavskiyDr Andrey BoguslavskiyDr Hongbin DingDr Hongbin Ding

Hons. StudentsHons. StudentsChris MorrisChris Morris

Jenna JoesterJenna JoesterGerry O’ConnorGerry O’ConnorHoi-Ming ChanHoi-Ming Chan

PostdocPostdocDr Masakazu NakajimaDr Masakazu Nakajima

ColleaguesColleaguesProf. Scott KableProf. Scott KableDr Klaas NautaDr Klaas Nauta

Thanks toThanks toCoblentz SocietyCoblentz Society

$ARC funding$$ARC funding$

PhD StudentsPhD Students(Dr) Damian Kokkin(Dr) Damian Kokkin

(Dr) Neil Reilly(Dr) Neil ReillyTyler TroyTyler Troy

Nahid ChalyaviNahid Chalyavi

Cation spectroscopy – e.g. C4H2+

Spectra of Arn-C4H2+

Schmidt et al., J. Molec. Spectrosc.

Spectra are too perturbed for our purposesHave to break covalent bonds… hard!

C=C

Stre

tch

C≡C

Stre

tch

conformer specific DF

Fingerprint region

Prop

argy

l/Vi

nyl-w

ag

A chemical test…

3-phenylprop-1-yne 1-phenylprop-1-yne

Huge signal (50x greater than benzene)

About same signal as benzene