MICROWAVE, MILLIMETER-WAVE, AND SUBMILLIMETER-WAVE SPECTRA OF 1,1,1-TRIFLUOROPROPYNE - ANALYSIS OF THE GROUND AND UPSILON(10)=1 VIBRATIONAL-STATES AND OBSERVATION OF DIRECT L-TYPE RESONANCE TRANSITIONS

The rotational spectrum of CF3C=CH was measured up to 650 GHz in the g round state (about 220 transitions up to J = 112). A centrifugal disto rtion analysis was performed and all the sextic constants were accurat ely determined. The failure to observe the splitting of the K = 3 line s indicates that the splitting constant h3 is smaller than 10(-5) Hz. In the lowest bending vibrational state upsilon10 = 1, the rotational spectrum was measured up to 470 470 (289 transitions up to J = 78). Fu rthermore, 344 direct l-type resonance transitions were observed betwe en 2 and 23 GHz up to J = 84 by microwave Fourier-transform spectrosco py. Two sets of parameters were used to fit the data. In addition to a strong ''2, 2'' l-type interaction, it was necessary to take into acc ount a ''2, -4'' interaction, which explains the splitting of the kl = -2 levels. A third interaction also had to be included in the fit: ei ther the ''0, +/-3'' interaction or the ''2, -1'' l-type one. Both set s result in the same superb standard deviation of the fit. This is due to an ambiguity of the effective Hamiltonian which may be reduced in an infinite number of different manners. The unitary equivalence of bo th sets of parameters is verified experimentally. It must also be note d that the axial rotational constant A10 could be determined accuratel y. (C) 1994 Academic Press, Inc.