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Interrogating hydrocarbon radicals
Timothy Schmidt University of Sydney New South Wales, Australia
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Basel, Switzerland Maier Group
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Where is Basel? Here
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More specifically… Basel
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The locals…
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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: d Sco – C atoms per 106 H atoms z Oph – C per 106 H atoms …available for molecules and dust grains! (Dude, where’s my carbon)?
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Looking for the carbon 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 FA13 MOLECULAR EMISSION STRUCTURE IN THE RED RECTANGLE - SEQUENCE BANDS?
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Thought to be due to carbonaceous molecules (cations probable)
Properties of the DIBs 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 appropriated from Ben McCall (www)
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DIBs 10% of light missing at this wavelength
Hobbs et al a catalog of diffuse interstellar bands in the spectrum of HD due to gas phase molecules… what are they? 10
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Carbon Chains HC2nH HC2n+1H px py px py
Largest identified interstellar molecules are carbon chains. Oscillator strengths can be huge… less material required. 11
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Electrical Discharge Source
High pressure gas (Ar) Vacuum Pulsed nozzle C16Hn C14Hn C12Hn C17Hn HCCH C15Hn C10Hn C13Hn HCCH C8Hn C11Hn C6Hn C9Hn HV HCCCCCCCCCCCH HCCCCCCCCCCCCCCCH cold molecules in centre of beam
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Resonance 2-Colour 2-Photon Ionization (R2C2PI)
Detector Source Extraction of ions TOF MS Ionization continuum +e- l2 l1 Chamber in Sydney 13
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HC2nH B1Su+ ← X1Sg+ Pino et al., JCP 114, 2208
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HC2nH A1Du/Su- ← X1Sg+
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HC2nH A1Du/Su- ← X1Sg+ Ding et al., PCCP 5, 4772 (2003)
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HC2n+1H A3Su- ← X3Sg-
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B ← X transitions carry the oscillator strength
LUMO SOMO + HOMO
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No matches to DIBs for carbon chains
Longer chains must be measured HC19H in UV, HC26H in UV HCCCCCCCCCCCCCCCCH HCCCCCCCCCCCCCCCH HCCCCCCCCCCCCCH HCCCCCCCCCCCH HCCCCCCCCCH HCCCCCCCCCCS HCCCCCCCH HCCCCCCCCS HCCCCCCS HCCCCS
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C2n+1H3 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-H
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Some more new molecules
CH3CCCCCCCH HCCCCCCCH
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Some more new molecules
H-C☰C-C ☰ C- CH3 | C -C☰C-C ☰ C-H H-C☰C-C ☰ C- H | C -C☰C-C ☰ C-H
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Still no match to DIBs 2004 MJ13 2004 WA03 H-C☰C-C ☰ C-
C-C ☰ C-C ☰ C-H H-C☰C-C ☰ C- C-C ☰ C-H CH3CCCCCCCH H-C☰C-C ☰ C- H | C -C☰C-C ☰ C-H HCCCCCCCCCCCCCCCCH H-C☰C-C ☰ C- CH3 | C -C☰C-C ☰ C-H HCCCCCCCCCCCCCCCH HCCCCCCCCCCCCCH HCCCCCCCCCCCH 2004 MJ13 2004 WA03 HCCCCCCCCCH HCCCCCCCCCCS HCCCCCCCH HCCCCCCCCS HCCCCCCS HCCCCS
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Sydney, Australia
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Laser spectroscopy supergroup 2009
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RRB spectrum - fluorescence
Red Rectangle and DIBs DIB spectrum 5799Å RRB spectrum - fluorescence Sarre et al., Science 269 (1995)
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The Red Rectangle Aromatic material? The “Unidentified Infrared Bands”
- believed due to aromatic material in Interstellar medium. Aromatic material?
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Kwok, Nature 430, 895 (2004)
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C2 Swan bands in Red Rectangle
d3Pg v=2 v=1 v=0 Swan system, Wollaston 1802 v=2 v=1 v=0 a3Pu Rob Sharp AAO
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C6H6 discharge High pressure gas (Ar) Vacuum Pulsed nozzle C6H6 C6H6 ? 4429Å DIB HV ? cold molecules in centre of beam Unidentified CRDS laboratory spectrum from Thaddeus/McCarthy lab Jet-cooled CRDS spectrum obtained in Basel Can fluorescence spectroscopy help?
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C6H6 discharge – laser induced fluorescence
? C3 ? ? ? ? ? Dr Neil James Reilly (sold to McCarthy)
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Benzene discharge Fluorescence of a benzene discharge C2
(normal fluorescence excitation spectrum) Fluorescence of a benzene discharge C2 Not C2 !!
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Some electronic states of C2
d3Pg v=2 A1Pu v=1 c3Su+ v=0 v=2 v=2 d-c system Not seen until 2006 v=1 v=1 v=0 v=0 b3Sg- Swan system 1802 Phillips system 1948 v=2 v=1 v=0 Ballik-Ramsay system 1958 v=2 v=2 v=1 v=1 v=0 v=0 a3Pu X1Sg+
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c3Su+ state of C2 pg d-c Swan sg pu su sg
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d-c system observed!
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d-c system observed 2006 RC07; 2007 RD03
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Kokkin-Reilly-Morris-Nakajima-Nauta-Kable-Schmidt?
Named band systems Kokkin-Reilly-Morris-Nakajima-Nauta-Kable-Schmidt?
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Inspiration Kokkin, Reilly, Morris, Nakajima, Nauta, Kable and Schmidt, JCP (2006)
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Back to the C6H6 discharge..
? ? ? ? C2 ? ? ? ?
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Dispersed fluorescence
origin DF
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? = same molecule! ? ? ? ? ? ? C2 ? ?
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2DF spectrum of benzene discharge
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2DF spectrum of CH R-R R-P R-Q Q-Q Q-R Q-P C3 P-P P-Q P-R
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2DF spectrum of benzene discharge
476 nm
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Set detection window over molecule X
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Single species spectrum
1000 cm-1 = ring breathe? = aromatic?
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Measure the mass… Damian Kokkin Dr Damian Leigh Kokkin
(sold to McCarthy) Damian Kokkin
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Measure the mass… S0 S1 l l/2 1+1’ REMPI Damian Kokkin
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R2C2PI mass 115 mass (X) = 115 X = C9H7 LIF R2C2PI m/z=115
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Possible isomers of C9H7 (that are aromatic)
3-phenylpropargyl 1-phenylpropargyl Indenyl radical IP too high Maybe Maybe
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Some ground state frequencies (cm-1)
Experiment B3LYP/ 6-311G**×0.97 n29 121 120 n28 319 320 n27 422 422 n26 620 609 n25 630 620 n24 674 652 n23 823 810
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Resonance-stabilized radicals
+ CH4 1P1P + •CH3 DH = 60kJ/mol 3PPR I think I mentioned to you that the RSE of 3VP from experiment is ~60kJ/mol, that of 1VP is ~110kJ/mol. + CH4 3P1P + •CH3 DH = 100kJ/mol 1PPR Data from Prof. Leo Radom (USyd)
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1PPR not a DIB carrier Hobbs et al a catalog of diffuse interstellar bands in the spectrum of HD 55
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1PPR also produced from 1-hexyne…
462nm 471nm this is not noise, it is fluorescence from multiple species LIF with small mono, asterisked peaks were dispersed
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2dF… emission excitation
LIF with small mono, asterisked peaks were dispersed excitation
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dispersed fluorescence of a1
most intense emission feature seen in 2d trans 1-VP 3-VP sym Mode Exp. (cm⁻¹) Calculated (cm⁻¹) a' 17 169 165 138 16 390 386 322 15 540 523 13 910 900 1010 12 1064 1067 1041 11 1127 1153 1247 10 1265 1261 1278 9 1304 1302 1400 7 1496 1504 1526 6 2024 2044 1985 111 101 71 151 121 61 161 91 131 trans 1-vinylpropargyl 171 1000 2000 3000
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two conformers 3463 cm⁻¹ 3634 cm⁻¹ D=168 cm⁻¹ (G3B3 level of theory)
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dispersed fluorescence of b1
origin transition of cis 1-vinylpropargyl cis 1-VP 3-VP sym Mode Exp. (cm⁻¹) Calculated (cm⁻¹) a' 17 155 153 138 16 373 322 15 642 620 523 13 932 914 1010 12 1019 1011 1041 11 1111 1122 1247 10 1217 1223 1278 9 1396 1371 1400 7 1503 1508 1526 6 2032 2058 1985 101 111 171 121 61 161 71 151 131 91 1000 2000 3000
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also not DIB carrier Hobbs et al a catalog of diffuse interstellar bands in the spectrum of HD 61
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not DIB carrier Hobbs et al a catalog of diffuse interstellar bands in the spectrum of HD 62
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Of course, no match to DIBs
2006 WH07 (not) IDENTIFYING FLUORESCENT HYDROCARBON RADICALS FROM A BENZENE DISCHARGE. H-C☰C-C ☰ C- C-C ☰ C-H H-C☰C-C ☰ C- C-C ☰ C-C ☰ C-H CH3CCCCCCCH H-C☰C-C ☰ C- H | C -C☰C-C ☰ C-H HCCCCCCCCCCCCCCCCH H-C☰C-C ☰ C- CH3 | C -C☰C-C ☰ C-H HCCCCCCCCCCCCCCCH HCCCCCCCCCCCCCH HCCCCCCCCCCCH HCCCCCCCCCH HCCCCCCCCCCS HCCCCCCCH HCCCCCCCCS HCCCCCCS HCCCCS
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Resonance-Stabilized Hydrocarbon Radicals
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Resonance-Stabilized CnHm Radicals
? Indene adds H barrierlessly to afford the 1-indanyl radical
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Indanyl radicals 2009 TJ09 Free to a good home in 2011
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2010 WG09 - Chalyavi Red rectangle nebula 1-naphthylmethyl
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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 69
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Benzene-like orbitals
LUMOs HOMOs Is the transition B2u – A1g, like benzene? 70
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A D3h jewel Jahn-Herzberg-Teller2 ? Jahn-Teller… E” Herzberg-Teller?
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(sigh) H-C☰C-C ☰ C- C-C ☰ C-H H-C☰C-C ☰ C- CH3 | C -C☰C-C ☰ C-H
CH3CCCCCCCH H-C☰C-C ☰ C- C-C ☰ C-C ☰ C-H H-C☰C-C ☰ C- H | C -C☰C-C ☰ C-H HCCCCCCCCCCCCCCCCH HCCCCCCCCCCCCCCCH HCCCCCCCCCCCCCH HCCCCCCCCCCCH HCCCCCCCCCH HCCCCCCCCCCS HCCCCCCCH HCCCCCCCCS HCCCCCCS HCCCCS
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Acknowledgments from Basel. 2001-2003
Prof. John P. Maier Dr Thomas Pino Dr Andrey Boguslavskiy Dr Hongbin Ding
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Colleagues Thanks to Coblentz Society Postdoc $ARC funding$
Prof. Scott Kable Dr Klaas Nauta Thanks to Coblentz Society Postdoc Dr Masakazu Nakajima $ARC funding$ PhD Students (Dr) Damian Kokkin (Dr) Neil Reilly Tyler Troy Nahid Chalyavi Hons. Students Chris Morris Jenna Joester Gerry O’Connor Hoi-Ming Chan
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Cation spectroscopy – e.g. C4H2+
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Spectra of Arn-C4H2+ Spectra are too perturbed for our purposes
Have to break covalent bonds… hard! Schmidt et al., J. Molec. Spectrosc.
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conformer specific DF Fingerprint region Propargyl/ C=C Stretch
Vinyl-wag C=C Stretch C≡C Stretch
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(50x greater than benzene)
A chemical test… 3-phenylprop-1-yne 1-phenylprop-1-yne About same signal as benzene Huge signal (50x greater than benzene)
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