FAR-INFRARED SPECTRUM OF N-2 AND N-2-NOBLE GAS-MIXTURES NEAR 80 K

The far-infrared absorption spectra of gaseous nitrogen, and mixtures of nitrogen with the foreign gases argon and neon, have been measured at pressures near 1 atm. and at temperatures near 78 and 89 K. Spectra were obtained over the wave number range 20-100 cm(-1) using a Fourie r transform spectrometer and a multiple reflection absorption cell of 52 m path length. They show a broad continuum associated with the pure rotational collision-induced S branch of the N-2 molecule plus struct ure attributed to transitions in dimers, not previously observed in th is spectral region. In the case of N-2-Ar, there are strong similariti es with the fundamental vibrational band under similar conditions of p ressure and temperature as reported by McKellar [J. Chem. Phys. 88, 41 90 (1988)]. The integrated absorption coefficient has been evaluated f or the N-2-N-2 rotational band; at 78 K it equals 3.1 x 10(-31) cm(5) sec(-1), a factor of 2 greater than typical values at temperatures abo ve 100 K. (C) 1996 American Institute of Physics.