Gas phase molecular relaxation at very low temperatures.: A comparative study of N2 and its mixtures with He and Ne

The low temperature (< 100 K) relaxation of N-2 in self-collisions and in collisions with He and Ne has been experimentally studied with resonance-enhanced-multiphoton-ionization and time-of-flight techniques. The following average values of the rotational relaxation cross sections, a,, have been derived from the measurements: sigma(r2)(N2-N2) (T = 5 60 K) approximate to 35 Angstrom(2); sigma(r)(N2-He) (T=5-80K) approximate to 15 Angstrom(2) and sigma(r)(N2-Ne) (T=5-60K) approximate to 40 Angstrom(2). The cross section trend sigma(r)(N2-N2) approximate to sigma(r)(N2-Ne) > sigma(r)(N2-He) reported in the literature for T = 300 K is confirmed below 100 K, but the absolute values are larger in the low temperature range. (C) 2002 Elsevier Science Ltd. All rights reserved.