1. MICROWAVE SPECTRA FOR THE THREE 13C1 ISOTOPOLOGUES OF PROPENE AND NEW ROTATIONAL CONSTANTS FOR PROPENE AND ITS 13C1 ISOTOPOLOGUES
NORMAN C. CRAIG, Department of Chemistry and Biochemistry, Oberlin College, Oberlin, OH, USA
PETER GRONER, Department of Chemistry, University of Missouri–Kansas City, Kansas City, MO, USA
ANDREW R. CONRAD, RANIL GURUSINGHE, MICHAEL J. TUBERGEN, Kent State University, Kent, OH, USA

2. Goals for this work
Measure new MW spectra in the GHz region for propene and its three 13C1 isotopologues.
Improved fit of the rotational constants for propene with the ERHAM internal rotor program.
Improved fits of the rotational constants for the three 13C1 isotopologues of propene with ERHAM.
Rotational constants for use in determining an improved semiexperimental equilibrium structure of propene.
Prior work: J. Demaison and H. D. Rudolph, J. Mol. Spectrosc. 2008, 248,

3. Normal Propene

4. MW Spectroscopy at Kent State
Mini Balle-Flygare jet-beam, FT instrument, as developed by R. D. Suenram et al. at NIST.
10-22 GHz region.
Doppler doublets with pulsed valve in the middle of the fixed mirror.
Dipole moments of propene: a 0.360±0.001 D; b 0.05±0.02 D. D. R. Lide, Jr. and D. E. Mann, J. Chem. Phys. 1957, 27,
A and E components due to the CH3 internal rotor.

6. Rotational Constants for Propene
27-parameters fitted: 14 rotational and centrifugal distortion constants. Others related to internal rotation. Insufficient rotational data for vibrational excitation to determine a value for the rotational barrier.

7. MW Spectra of Three 13C1 Species
Pure sample of 3-13C1 species ($$); other two in natural abundance.
J = 1-2 a-type transitions from cw measurements used in fitting with reduced weight.
D. R. Lide, Jr.; D. E. Mann, J. Chem. Phys. 1957, 27,
D. R. Lide, Jr.; D. Christensen, J. Chem. Phys. 1961, 35,
All but four rotational constants (ΔJK, δJ, β, ε1) in addition to A0, B0, and C0 transferred from the normal species.

11. Conclusions
Improved rotational constants for propene fitted with ERHAM to 890 lines; 27 parameters.
Good agreement of observed centrifugal distortion constants with ones computed with the B3LYP/cc-pVTZ model.
Improved rotational constants for the three 13C1 isotopologues fitted with ERHAM.
Determining a semiexperimental equilibrium structure for propene is underway.

12. Acknowledgments Dreyfus Foundation (Senior Scholar Mentor
Grant to N.C.C.)
Department of Chemistry, Kent State University
Department of Chemistry and Biochemistry, Oberlin College