Collision-induced absorption of the first overtone bands of H₂ and D₂

Enhancement spectra of the collision-induced absorption (CIA) of H₂ in its first overtone region 7500- 9500 cm⁻¹ in binary mixtures H₂ - N₂ and H₂ - CO were studied at 298 K for base densities of H₂ in the range 89 - 145 amagat and for partial densities of N₂ and CO in the range 19 - 392 amagat. The observed spectra consist of the quadrupolar double transitions: Q₂(J) (H₂) + S₀(J), O₀(J) and Q₀(J) (N2/CO), O₂(J) (H₂) + Q₀(J) (N₂/CO) and S₂(J) (H₂) + Q₀(J) (N₂/CO) with J = 0 to 4 for H₂ and J = 1 to 25 for N₂/CO. Enhancement absorption profiles of H₂-N₂ and H₂-CO were modelled by a total of 434 components of quadrupolar double transitions. The observed spectra agree with theoretical spectra and confirm that the isotropic overlap induction is absent in the 2 - 0 band of H₂ unlike in the CIA spectra of the fundamental band of H₂. The present analysis also confirms that there is no contribution from the electric dipole of CO to the induction mechanism in H₂ - CO mixtures. -- CIA spectra in the first overtone region from 5250 to 7250 cm⁻¹ of pure D₂ were studied at 77, 201 and 298 K. The observed spectra were modelled by a total of 92, 214 and 267 components of double vibrational transitions respectively. Enhancement spectra of the CIA in the first overtone region 5000 to 7000 cm⁻¹ of D₂ in D₂ - N₂ were studied at 298 K for a base density of D₂ of 73 amagat and for partial densities of N₂ in the range 150 - 370 amagat. The observed spectra were modelled with a total of 1176 components of double vibrational transitions. Enhancement spectra of the CIA in the first overtone region 5500 to 6750 cm⁻¹ of D₂ in the D₂-Ar, D₂-Kr and D₂-Xe binary mixtures were studied at room temperature for base densities of D₂ in the range 55 to 251 amagat and for partial densities of Ar, Kr and Xe in the range 46 to 384 amagat. The observed spectra consist of the following quadrupolar transitions: O₂(3), O₂(2), Q₂(J), J = 1 to 5 and S₂ (J), J = 0 to 5 of D₂. -- The observed spectra confirm that the isotropic overlap interaction does not contribute to the absorption of the first overtone band, unlike in the CIA spectra of the fundamental band. The binary and ternary absorption coefficients were determined from the integrated absorption coefficients of the band. Profile analysis of the observed spectra was carried out using the Birnbaum-Cohen line shape function for each component of the band and the characteristic half-width parameters δ₁ and δ₂ for the transitions were determined