Collision-induced spectra of double vibrational transitions of H₂ (V = 1 ← 0) + N₂ (V = 1 ← 0) AT 201 K AND 298 K

Abstract

In the present research project a systematic experimental study of the collision-induced absorption (CIA) spectra of the double fundamental vibrational transitions H₂ (v = 1 ← 0 + N₂ (v = 1 ← 0) was undertaken for the first time in the spectral region 5600 – 7600 cm -1. The experiments were carried out with a 2.0 m high-pressure, low-temperature transmission cell in binary mixtures of H₂ and N₂ at 201 K and 298 K for partial densities of H₂ and N₂ in the ranges 60 to 400 and 100 to 350 amagat, respectively. -- The observed spectra are interpreted in terms of the double transitions: O₁(3) + Q₁(J ) • O₁(2) + Q₁(J ) • Q₁(J ) + O₁(J ) • Q₁(J ) + Q₁(J ) • Q₁(J ) + S₁( J ) • S₁(0) + Q₁(J ) • S₁(1) + Q₁(J ) • S₁(2) + Q₁(J ) • and S₁(3) + Q₁(J ) • in which the first component is from H2 and the second component is from N₂. These transitions occur on the high wavenumber wing of the enhancement of the CIA fundamental band of H₂ in H₂-N₂ mixtures. Various semi-empirical line shapes were attempted in the analysis of the observed spectra. Lewis-Birnbaum-Cohen (LBC) lineshape function is found to give the best fit of the calculated profiles to the experimental profiles. The lineshape parameters τ₁, and τ₂ are found to have a linear dependence on the partial density of ρΝ₂ of nitrogen. In particular, τ₁ increases with ρΝ₂, thus showing pressure-narrowing of the linewidth parameter δ₁ (=1/2πστ₁ ) as the density increases. Finally the binary and ternary absorption coefficients of the double vibrational transitions of H₂+N₂ were calculated.