Post on 14-Jan-2016
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