1. The far infrared spectrum of thiophosgene Analysis of the 2 and 4 fundamental bands at 500 cm-1 A.R.W. McKellar National Research Council of Canada, Ottawa B.E. Billinghurst Canadian Light Source, University of Saskatchewan, Saskatoon

2. Cl S Cl Thiophosgene is a formaldehyde analog Planar, C2v symmetry
Near-oblate ‘accidental’ symmetric top
A ~ 3557 MHz
B ~ 3464 MHz
C ~ 1753 MHz
The axes ‘switch’ with isotopic substitution:
For 35Cl2CS, the S-C symmetry axis is the a-inertial axis
For 37Cl2CS, the S-C symmetry axis is the b-inertial axis S Cl

3. Thiophosgene is very popular for studying IVR, intersystem crossing, etc. It’s one of the best-characterized of all molecules in terms of vibrational level structure.
But there are no previous systematic high-resolution IR studies.

4. Why no previous IR studies? Congested spectra!
35Cl35Cl12C32S
v = 0
0.337
35Cl37Cl12C32S
0.220
v3 = 1
0.074
v6 = 1
0.068
0.048
0.044
37Cl37Cl12C32S
0.036
v4 = 1
0.030
v2 = 1
0.026
0.020
0.017
35Cl35Cl12C34S
0.015
35Cl37Cl12C34S
0.010
0.008
0.007
Etcetera!!!
Relatively heavy molecule
Isotopic dilution
Hot band dilution
The ground state of the principal isotope has only about one third of the total population at room temperature!

5. 3 6 4 2 5 1 Microwave study
C-Cl bend
295 cm-1 6
C-Cl rock
312(?) 4
out of plane bend
471 2
C-Cl sym stretch
504 5
C-Cl asym stretch
813 1
C-S stretch
1135
Microwave study
Carpenter, Rimmer, Smith, & Whiffen J. Chem. Soc. Faraday Trans , (1975)
First complete vibrational assignment
Frenzel, Blick, Bennett, & Niedenzu J. Chem. Phys. 53, (1969)

6. 2001 survey spectrum from NRC: Bomem DA8 spectrometer, resolution 0
2001 survey spectrum from NRC: Bomem DA8 spectrometer, resolution cm-1

7. CLS Parameters Energy: 2.9 GeV Current: 200 mA Circumference: 171 m
12 straight sections, 5.2 m long
RF: 500 MHz, 2.4 MV, supercon
Injection: 250 MeV LINAC full energy booster ring
Main building: ~ 85 x 85 m

9. Nominal resolution = 0. 00096 cm-1 Unapodized instrumental width = 0
Nominal resolution = cm-1 Unapodized instrumental width = cm-1 Cl2CS Doppler width = cm-1
Pressure = Torr Path = 40 m

10. resolution matters!

14. 2 band
35Cl35ClCS: lines assigned ~3500; rms error ~ cm-1 (2 MHz)
35Cl37ClCS: lines assigned ~1330; rms error ~ cm 0 = cm-1
A' - A" = -8.3 MHz
B' - B" = -2.3 MHz [for 35Cl35ClCS]
C' - C" = -3.0 MHz
4 band
a few hundred lines assigned 0 = cm-1
A' - A" = MHz
B' - B" = +0.6 MHz [for 35Cl35ClCS]
C' - C" = +1.9 MHz

15. Thiophosgene -- Future Work
Extend & complete analysis of the 4 band
Coriolis interaction between 2 and 4 ?
Can hot bands or isotope be assigned ??
Study 3 band ~292 cm-1
Study 6 band ~312 cm-1 (?!?)