1. The Microwave Spectrum of the Mono Deuterated Species of Methyl Formate HCOOCH 2 D L. H. Coudert, a L. Margulès, b G. Wlodarczak, b and J. Demaison b a LISA, CNRS/Paris 12 University, Créteil, France b PhLAM, CNRS/Lille I University, Villeneuve d’Ascq, France

2. Overview The normal species The data Mono deuterated species PEF Energy level calculation Analysis results

3. The normal species It is a molecule of astrophysical interest which has been the subject of many investigations. Non-rigid molecule displaying internal rotation of the methyl group. 4270 transitions measured for the A and E-species up to J  62 and within v t  0 and 1. The barrier to internal rotation is V 3 = 370 cm 

4. PEF of the mono deuterated species HCOOCH 3

5. HCOOCH 2 D 10 cm 

6. Tunneling sublevels HCOOCH 3 405 MHz HCOOCH 2 D 81.8 MHz ~10 cm  For J  0, the rotational dependence of the tunneling splitting must be taken into account. The IAM water dimer 1 formalism will be used. 1. Hougen, J. Mol. Spec. 114, 395 (1985) & Coudert and Hougen, J. Mol. Spec. 130, 86 (1988)

7.  eq   eq   eq  h 2,  2,  2,  2 h 0,  0,  0,  0

8. ParametersNumberRelation h 2,  2,  2,  2 3  2   2   h 0,  0,  0,  0 0not used A, B, C3D in plane A, B, C3D out of plane Spectroscopic parameters 9 zeroth order parameters

9. Rotational dependence of the tunneling J 0,J J 2,J  2 J 4,J  4 J 6,J  6 J 8,J  8 J 10,J  10 J 12,J  12

10. Rotational dependence of the tunneling J 1,J J 3,J  2 J 5,J  4 J 7,J  6 J 9,J  8 J 11,J  10 J 13,J  12

11. Rotational dependence of the tunneling High K c -values, tunneling depends on K c only

12. The data RangeUncertainty NTechnique 7 to 70 GHz150 kHz 352Stark 150 to 650 GHz 30 kHz1126BWO Max J is 61, max K a is 42 1042 a-type and 435 b-type with  v  0

13. Analysis results Data NRMS 7 to 70 GHz 3520.232 MHz 150 to 650 GHz11260.189 MHz All14780.200 MHz Unitless standard deviation is 4.3

14. Spectroscopic parameters D out of plane configurations

15.  2 and  2 calculation 1. Hougen, J. Mol. Spec. 114, 395 (1985) & Coudert and Hougen, J. Mol. Spec. 130, 86 (1988) Values for  2 and  2 can be calculated from the geometry of the molecule along the tunneling path. 1

16. Tunneling splitting rotational dependence Using the structure of Curl: 1 1. Curl, J. Chem. Phys. 30, 1529 (1959)