1. Laboratory rotational spectrum and astronomical search of S-methyl thioformate
A. Jabri, I. Kleiner, L. Margulès, R. Motyenko, J-C. Guillemin, E. A. Alekseev, B. Tercero and J. Cernicharo

2. S-methyl thioformate : O-methyl thioformate :
Methyl formate: many lines detected in the interstellar medium
E. Chruchwell and G. Winnewisser, Astron. Astrophys., 45, (1975).
S-methyl thioformate :
MSCHO
O-methyl thioformate :
MOCHS

3. Astrophysical interest for sulfur bearing molecules
Important for understanding the chemical evolution of hot cores; molecular ratios used as chemical clocks to get information about the age of hot cores (Charnley et al 1997, Wakelam et al 2004, 2011)
BUT the chemistry of interstellar sulfur still undertermined:
Much less sulfur found in the dense regions of ISM than in diffuse regions (Anderson et al 2013)
Mystery about this missing sulfur, what are the reservoir(s) ?
About 20 sulfur-containing molecules identified so far but very few with internal rotors :
-CH3SH with observable A-E splittings (Linke et al 1979, Müller et al 2016)
-Ethyl mercaptan CH3CH2SH in Orion (Kolesnikova et al 2014), no A-E splittings

4. DMS ? Dimethyl ether: detected in the interstellar medium
Snyder et al., Astrophys. J. 191, L79-L82 (1974).
Search for dimethyl sulfur? So far without success in orion
Jabri et al., Astonom. And Astrophys.589, A127 (2016)
DMS ?

5. S- Methyl thiodformate CH3SCHO: Previous works
1) Ab initio calculations
Senent, Puzzarini, Hochlaf, Dominguez-Gomez, Carvajal, J. Chem. Phys 141, (2014)

6. q (degrees)
q (degrees)
a (degrees)
Senent, Puzzarini, Hochlaf, Dominguez-Gomez, Carvajal, J. Chem. Phys 2014

7. Chemical synthesis of S-methyl thioformate
Methyl mercaptan
(or methanethiol)
Formic-acetic
Anhydride
Chemical synthesis of S-methyl thioformate
J-C Guillemin (Rennes) and A. Jabri

8. S- Methyl thiodformate CH3SCHO: Previous works
2) Microwave measurements
a) Jones et al 1976, J. Mol. Spectrosc. 60, 348 b)
22 A type lines and 15 E type lines fit to a few MHz
10 – 41 GHz

9. New millimeter measurements in Lille

10. Analysis of the spectrum of S-methyl thioformate
Previous experimental data measured by Jones et al. and by Caminati et al. was fit between 10 GHz and 41 GHz. We used the BELGI-Cs program in order to optimize different rotational constants.,
2256 new millimeter lines assigned with J and Ka values
up to 70 and 30, vt = 0

11. Microwave data from Caminati et al (1981)
Results: fits for the S-methyl thioformate vt=0 (BELGI-Cs)
Microwave data from Caminati et al (1981)
Millimeter data
New measurements
Number of lines 51
2137/ 117 /2
Weight (in kHz)
 150
 45/100/150
rms (in kHz)
 91
 27.8/84.6/90.6
Total: 2307 lines fit to 35.6 kHz
J and Ka values up to 70 and 30
34 parameters

13. Conclusion
2307 lines of the ground torsional state vt = 0-0-methyl thioformate fit to 35.6 kHz, J and Ka values up to 70 and 30 
A prediction of line positions and intensites is ready for astrophyscical search

14. Marion Kirmann Stage filé février-mai 2016 25/05/2016
Work in progress: Experimental spectrum recorded for the O-methyl thioformate
Millimeter spectrum(Lille) between 150 and 330 GHz: 849 lines assigned,
Preliminary fit
Molécule synthétisée & analysée au laboratoire PhLAM de Lille (Laboratoire de Physique des Lasers, Atomes et Molécules)
Complexité du spectre 1 pic : 1 transition entre niveaux d’énergie : attribuer chaque pic en théorie
(Règles de sélection ? Détailler JKaKc ?)
Marion Kirmann Stage filé février-mai /05/2016

15. Aknowledgments:
Jabri would like to thank the french groupe de recherche
SPECMO for travel grant to Lille
We thank the french Programme de Physique et Chimie du
Milieu Interstellaire (PCMI) for funding