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Rotational spectroscopy of thioformaldehyde, H2CS,in its four lowest excited vibrational, Coriolis-coupled states
Holger S. P. Müller, C. P. Endres, S. SchlemmerA. Maeda, I. Medvedev, E. Herbst, M. Winnewisser, F. C. De Lucia
62nd International Symposium on Molecular Spectroscopy; WG04
Motivation
• important molecule in interstellar medium
• textbook example for Coriolis interaction
v = 0
v3 = δs(CH2)
v2 = v(CS)
v1 = vs(CH2) v5 = vas(CH2)
v6 = ρ(CH2)v4 = oop1455.496
1059.205990.185 991.019
2971.03 3024.62
A1 B1 B2
Previous Work
• v = 0: presentation TI08 by Atsuko Maeda et al.
• v3, v4, v6 laser Stark spectroscopy: Bedwell & Duxbury, JMSp 84 (1980) 531 est. err.: 0.001 cm−1, some larger residuals
• v3, v4, v6 FTIR spectroscopy: P. H. Turner et al., JMSp 88 (1981) 402 est. err.: 0.010 cm−1, some larger residuals
• v2 FTIR spectroscopy: McNaughton & Bruget, JMSp 159 (1993) 340 est. err.: 0.0005 cm−1, 84 lines with larger residuals omitted
• also: v3, v4, v6 FTIR spectroscopy by W. J. Lafferty et al. (TC07)
Current Work
pyrolysis of c-C3H6S (trimethylene sulfide) → H2CS
OSU: FASSST (BWOs) 120 − 380 GHz ≡ J” = 3 – 9• complete & fast coverage• typical uncertainty: 100 kHz (used throughout)
Uni Köln: Cologne THz Spectrometer 574 − 670 GHz ≡ J” = 17, 18• phase-locked BWOs
• typical uncertainty: ~ 10 kHz (here: 5 − 50 kHz)
• selected transitions (~ 2J complete)• slower; high sensitivity
J = Ka energy levels I
E (cm−1)
2000
1500
1000
5
10
v4 = 1
5
10
v6 = 1
no Coriolis interaction
10
v6 = 1v4 = 1
5
with Coriolis interaction
intensity effects
asymmetry splitting in Ka = 4 I
1.31 MHz
asymmetry splitting in Ka = 4 II
anomalousK-splitting
−1.29 MHz
J = Ka energy levels II
E (cm−1)
2000
1500
1000
10
v6 = 1v4 = 1
55
2
8
5
10
v3 = 1
a weak line
J = Ka energy levels III
E (cm−1)
2000
1500
1000
10
v6 = 1v4 = 1
55
2
8
5
10
v3 = 1 v2 = 1
5
10
asymmetry splitting in Ka = 4 III
1.79 MHz
The Current Dataset*
• 27 misc. v = 0 MW and mmW lines
• 358 FIR v = 0 lines (McNaughton & Bruget)
• 372 (sub-) mmW lines from OSU
• 144 sub-mmW lines from Köln
• 76 − 10 ν3, ν4, ν6 lines from Bedwell & Duxbury
• 127 − 10 ν3, ν4, ν6 lines from Turner et al.
• 436 − 6 ν2 lines from McNaughton & Bruget
*) unresolved asymmetry splitting counted only once
Interaction Terms
iGaJa + iGaJ{Ja, J2} + iGaKJa3 + iG2a{Ja, J+
2 + J−2} + . . .
+Fbc{Jb,Jc} + . . .
A Satifactory Model
• S-reduction; 17 parameter for v = 0 (B, D, H + 2; 2 fixed)
• E + 4 to 6 × ΔX for each vi = 1
• 5 Gijg from own ab initio calc. (MP2/cc-pCVQZ); 3 released
• 0 – 7 distortion terms for each Gijg
rms error of 1.0
Spectroscopic Parameters (cm−1, MHz) of H2CS(or Differences)
v = 0 v4 = 1 v6 = 1 v3 = 1 v2 = 1
E 990.183 991.021 1059.205 1455.496
(Δ) A − (B + C)/2l 274439. − 476. −221. 2510.
(Δ) (B + C)/2 17175.747 −2.92 −11.70 −107.19 −27.39
(Δ) (B − C)/4 261.6240 −5.32 12.46 −1.26 6.73
(Δ) DK 23.7 − − − 2.05
(Δ) DJK × 10−3 522.3 −0.04 1.5 18.1
(Δ) DJ × 10−3 19.02 0.16 0.13 0.17 −0.10
+ 1 × Δd1 + 2 × ΔHKJ
Interaction Parameters (MHz)
X46a X24
b X34b X36
c
Gi 300219. 30846. 2032. 9140. GiK −59.3 7.1 0.109 −1.3 GiJ −0.819 −0.06 − −0.044 G2i 1.02 0.040 − 0.015