Aspects of collision-induced absorption of hydrogen and deuterium

Gillard, Paul G. (1983) Aspects of collision-induced absorption of hydrogen and deuterium. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Induced infrared absorption spectra of hydrogen in the fundamental and second overtone regions and of deuterium in the fundamental and first and second overtone regions were investigated over a wide range of gas densities. The spectra were recorded using a 2 m high-pressure low-temperature absorption cell which was modified by the addition of a vacuum jacket to allow the cell to be cooled by immersion in liquid nitrogen. Many of the spectra were recorded with a microprocessor-controlled data acquisition system designed specifically for this purpose. This device transmitted the data to one of the larger computers on campus for further analysis. -- The hexadecapole-induced U-transitions corresponding to a change of 4 in the rotational quantum number which occur in the high wavenumber wing of the hydrogen fundamental band were studied at a temperature of 77K over a density range 500-900 amagat and an analysis of the absorption profiles was carried out. -- In the fundamental band of deuterium, the weak S+S type double transitions arising from the anisotropy of the polarizability were studied at 77K. Induced spectra of deuterium in the first overtone region were studied at 77, 201 and 295K at gas densities in the range 100-450 amagat. The spectrum appears to have no contribution from the short-range electron overlap interaction, and the observed and theoretically predicted intensities for the individual components of the spectrum are not in good agreement. However, an “improvement factor” proposed for the available theoretical matrix elements of the quadrupole moment of deuterium produces good agreement between the observed and calculated profiles. The anisotropic S+S type transitions in the first overtone region were also studied at 77K for densities in the range 500-850 amagat. A distinct narrowing of the halfwidth of the spectral lines as a function of density was greater than 300 amagat at 77K. -- Induced spectra of both hydrogen and deuterium in the second overtone regions were recorded at 77K at densities in the range 500-930 amagat. In these spectra there is clear evidence of the contribution from the short-range overlap interaction. Transitions of the S+S type were also observed in the region of the 3-0 band of hydrogen. In the spectral region of the 3-0 bands the agreement between the observed intensities and the corresponding theoretically calculated values was rather poor.

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