THE MILLIMETER-WAVE AND SUBMILLIMETER-WAVE SPECTRUM OF PROPYLENE (CH3CHCH2)

The rotational-torsional spectrum of the internal rotor propylene (CH3CHCH2) has been extended into the millimeter-wave and submillimeter-wave regions of the electromagnetic spectrum. Approximately 760 lines belonging to the A and E torsional substates of the ground (upsilon(t) = 0) torsional state have been measured through rotational quantum number J = 30 and up to a frequency of 412 GHz. These lines have been added to approximately 40 previously measured rotational transitions in the microwave region to make up a data set which has been fit to 90 kHz using our internal axis method. The threefold potential barrier for torsional motion that we determine agrees well with previous values. The spectra reported here should be useful for interstellar searches for propylene, which should be directed toward high-mass star-forming regions, where the degree of saturation is higher than in quiescent sources. (C) 1994 Academic Press, Inc.