THE MM-WAVE ROTATIONAL SPECTRUM OF CBRCLF2 (HALON BCF) - OBSERVATION OF A NEW R-TYPE BAND AND GENERALIZATION OF CONDITIONS FOR OBLATE-TYPE BAND FORMATION

The rotational spectrum of the best known halon molecule, CBrClF2, was measured in the region 160-320 GHz. The data set was extended to J '' = 110 and the weak (b)Q and (a)R rotational transitions were also ass igned and measured. Accurate spectroscopic constants are reported for the ground state in the four most abundant isotopic species of the mol ecule, and for the lowest vibrational satellite in the (BrCl)-Br-79-Cl -35 and (BrCl)-Br-81-Cl-35 isotopic species. Broadband rotational spec tra showed an unusual diffuse R-type band characterized by quantum num ber changes Delta J = -1, Delta K--1 = 2, and Delta K-+1 = -3 between successive lines down the band. It is shown that this band is a varian t of the so-called type II bands, which will form under the most gener al oblate limit condition (A + B) = (l/m)2C, where m and l are integer s. Such bands are expected to be common in high-J rotational spectra a nd their key properties are given. (C) 1996 Academic Press, Inc.