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

The rotational-torsional spectrum of the internal rotor propylene (CH3 CHCH2) has been extended into the millimeter-wave and submillimeter-wa ve regions of the electromagnetic spectrum. Approximately 760 lines be longing to the A and E torsional substates of the ground (upsilon(t) = 0) torsional state have been measured through rotational quantum numb er J = 30 and up to a frequency of 412 GHz. These lines have been adde d to approximately 40 previously measured rotational transitions in th e 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 to rsional 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 regi ons, where the degree of saturation is higher than in quiescent source s. (C) 1994 Academic Press, Inc.