ETHYLENE HOT BANDS FROM MOLECULAR JET DOUBLE-RESONANCE SPECTROSCOPY

Part of the ν10 + ν9 ← ν10 hot-band spectrum, as well as a few lines of the ν7 + ν9 ← ν7 hot band of ethylene, C2H4, have been recorded in a free molecular jet using a double-resonance technique. The identification of the hot-band transitions starting from ν7 has been confirmed in a separate experiment on a (collision-free) molecular beam. Experimentally determined wave-numbers and intensities are given for 169 hot-band lines, 124 of which have been identified. Additional information on symmetry species and rotational energy of the lower levels of a number of as yet unidentified hot-band lines has been obtained from their relaxation behavior. The double-resonance spectra have been confirmed and completed at higher J and Ka values by spectra recorded with a difference frequency spectrometer. The analysis of the ν9 + ν10 state, based on 153 experimentally determined levels, takes into account b-type Coriolis interactions with ν7 + ν11 and ν1 + ν8 states and an anharmonic resonance with the 2ν4 + 2ν8 state, yielding a 0.003 cm-1 standard deviation. © 1990.