Variations in the strength of the infrared forbidden 2328.2 cm(-1) fundamental of solid N-2 in binary mixtures

We present the 2335-2325 cm(-1) infrared spectra and band positions, profil es and strengths (A values) of solid nitrogen and binary mixtures of N-2 wi th other molecules at 12 K. The data demonstrate that the strength of the i nfrared forbidden N-2 fundamental near 2328 cm(-1) is moderately enhanced i n the presence of NH3, strongly enhanced in the presence of H2O and very st rongly enhanced (by over a factor of 1000) in the presence of CO2, but is n ot significantly affected by CO, CH4, or O-2. The mechanisms for the enhanc ements in N-2-NH3 and N-2-H2O mixtures are fundamentally different from tho se proposed for N-2-CO2 mixtures. In the first case, interactions involving hydrogen-bonding are likely the cause. In the latter, a resonant exchange between the N-2 stretching fundamental and the O-18 = C-12 asymmetric stret ch of (OCO)-O-18-C-12-O-16 is indicated. The implications of these results for several astrophysical issues are briefly discussed. (C) 1999 Elsevier S cience B.V. All rights reserved.