Rotational spectroscopy of thioformaldehyde, H 2 CS, in its four lowest excited vibrational, Coriolis-coupled states Holger S. P. Müller, C. P. Endres, S. Schlemmer A. 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 v 3 = δ s (CH 2 ) v 2 = v(CS) v 1 = v s (CH 2 ) v 5 = v as (CH 2 ) v 6 = ρ(CH 2 ) v 4 = oop A1A1 B1B1 B2B2

Previous Work v = 0: presentation TI08 by Atsuko Maeda et al. v 3, v 4, v 6 laser Stark spectroscopy: Bedwell & Duxbury, JMSp 84 (1980) 531 est. err.: cm −1, some larger residuals v 3, v 4, v 6 FTIR spectroscopy: P. H. Turner et al., JMSp 88 (1981) 402 est. err.: cm −1, some larger residuals v 2 FTIR spectroscopy: McNaughton & Bruget, JMSp 159 (1993) 340 est. err.: cm −1, 84 lines with larger residuals omitted also: v 3, v 4, v 6 FTIR spectroscopy by W. J. Lafferty et al. (TC07)

Current Work  pyrolysis of c-C 3 H 6 S (trimethylene sulfide) → H 2 CS  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 = K a energy levels I E (cm −1 ) v 4 = v 6 = 1 no Coriolis interaction 10 v 6 = 1 v 4 = 1 5 with Coriolis interaction

intensity effects

asymmetry splitting in K a = 4 I 1.31 MHz

asymmetry splitting in K a = 4 II anomalous K-splitting −1.29 MHz

J = K a energy levels II E (cm −1 ) v 6 = 1 v 4 = v 3 = 1

a weak line

J = K a energy levels III E (cm −1 ) v 6 = 1 v 4 = v 3 = 1 v 2 =

asymmetry splitting in K a = 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 ν 3, ν 4, ν 6 lines from Bedwell & Duxbury 127 − 10 ν 3, ν 4, ν 6 lines from Turner et al. 436 − 6 ν 2 lines from McNaughton & Bruget *) unresolved asymmetry splitting counted only once

Interaction Terms iG a J a + iG a J{J a, J 2 } + iG aK J a 3 + iG 2a {J a, J J − 2 } F bc {J b,J c } +...

A Satifactory Model S-reduction; 17 parameter for v = 0 (B, D, H + 2; 2 fixed) E + 4 to 6 × Δ X for each v i = 1 5 G ij g from own ab initio calc. (MP2/cc-pCVQZ); 3 released 0 – 7 distortion terms for each G ij g  rms error of 1.0

Spectroscopic Parameters (cm −1, MHz) of H 2 CS (or Differences)

Interaction Parameters (MHz)