VIBRATION-ROTATION SPECTRA OF C-13 CONTAINING ACETYLENE .1. THE BENDING STATES UP TO UPSILON(4)+UPSILON(5)=2

Vibration-rotation spectra of 13C2H2 and 12C13CH2 have been recorded in absorption in selected regions between 50 and 1450 cm-1 at resolutions varying from 0.002 to 0.006 cm-1, with two different FT spectrometers. Many bands involving the bending modes ν4 and ν5 are present in this wavenumber range. Those with v4 + v5 = 2 have been analyzed by adopting a model Hamiltonian which accounts for the l-type resonances. All the relevant vibrational and rotational constants have been fitted for 13C2H2 whereas the anharmonic constant x044 could not be determined for 12C13CH2 because of the lack of observation of transitions involving the 2ν4 levels. The spectrum of 13C2H2 consisted of 1203 measured lines which required 38 molecular paramelers in order to obtain a good fit. The weaker spectrum of 12C13CH2 contained only 519 lines and 28 parameters were found to be sufficient. © 1993 Academic Press, Inc.