Collision-induced absorption spectra of binary mixtures of H₂ with D₂ and Ar and of pure HD

Hsieh, Chang-Tsang William (1992) Collision-induced absorption spectra of binary mixtures of H₂ with D₂ and Ar and of pure HD. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

In the present research project a systematic study of the collision-induced infrared absorption (CIA) spectra of the binary mixtures of H₂ - D₂ in the region of the double fundamental vibrations of H₂ and D₂ and H₂ - Aγ in the fundamental band of H₂, and of pure HD in its fundamental and first overtone regions was undertaken. The experiments were carried out with a 2.0 m high-pressure low-temperature transmission-type absorption cell at 77, 201 and 296 K at total gas densities up to 550 amagat. Infrared prism and grating spectrometers equipped with a microprocessor-controlled stepping motor were used to record the spectra. All the experimental results obtained represent first-time observations in collision-induced absorption. -- Collision-induced infrared absorption spectra of the double transitions of H₂(ν = 1 ← 0) and D₂(ν = 1 ← 0) have been observed at 77 and 201 K in the spectral region 7000-8000 cm⁻¹ for total gas densities up to 550 amagat with a partial gas density ratio of 1:1 of H₂ and D₂. The observed spectra are interpreted in terms of the transitions, Q₁(J) of H₂ + Q₁(J) of D₂, Q₁(J) of H₂ + S₁(J) of D₂, S₁(J) of H₂ - Q₁(J) of D₂, and S₁(J) of H₂ + S₁(J) of D₂ for J=0 and 1 for H₂ and J=0, 1, and 2 for D₂. Analysis of the experimental absorption profiles was carried out using appropriate lineshape functions. The absorption coefficients, lineshape parameters, etc., are obtained from the analysis. -- Collision-induced enhancement absorption spectra of the fundamental band of H₂ in H₂ - Aγ mixtures were recorded at room temperature for a base density of 72 amagat of H₂ for several partial densities of Aγ up to 440 amagat. Hexadecapole-induced U transitions, U₁(1), U₁(2), Q₁(0) + U⁰(1), and Q₁(1) + U₀(1) have been identified in the spectral region 5400-6200 cm⁻¹. A “cage” model has been proposed to account for the double transitions of H₂ – H₂ in the H₂ - Aγ enhancement spectra. From the analysis of the absorption profiles, the lineshape parameters and the absorption coefficients have been determined. -- The collision-induced absorption spectrum of the first overtone band of HD in the pure gas was observed at 77 K for gas densities up to 320 amagat. In addition to the allowed transitions P₂(1), R₂(0), and R₂(1), the CIA transitions Q₂(J) + Q₀(J), Q₁(J) + Q₁(J) + Q₂(J) + S₀(J), S₂(J) + Q₀(J), Q₁(J) + S₁(J), S₂(J) + S₀ (J), and S₁(J) + S₁(J) have been observed. An analysis of the observed absorption profiles has been completed. It is found that the isotropic overlap induction mechanism does not contribute to the intensity of the band and that negative contribution to the intensity of the band comes from the mixed term (2√3λ₃₂exp[-(R -σ)/ρ₃₂] << νJ | α | ν’J’ >< νJ | Q | ν’J’ > (R/α₀)⁻⁴. The fundamental band of HD has been investigated at 77 K for gas densities in the range 40-310 amagat. For the first time the collision-induced transitions of the type T₁(1) + Q₀(J), Q₁(J)+T₀ (1), U₁(0) + Q₀(J), Q₁(J) + U₀(0), V₁(0) + Q₀(J), and Q₁(J) +V₀(0) for HD have been identified. Here T, U, and V transitions correspond to ΔJ=3, 4, and 5, respectively.

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