Hydrogen vibration-rotation

Hydrogen is the most abundant chemical element in the universe, and in its various atomic and molecular forms furnishes a sensitive test of all of experimental, theoretical and computational methods. Vibration-rotational spectra of dihydrogen in six isotopic variants constituting all binary combinations of H, D and T have nevertheless been recorded in Raman scattering, in either spontaneous or coherent processes, and spectra of HD have been recorded in absorption. Despite the widely variable precision of these measurements, the quality of some data for small values of vibrational quantum number is still superior to that of data from electronic spectra [106], almost necessarily measured in the ultraviolet region with its concomitant large widths of spectral lines. After collecting 420... 

L. Wolniewicz. Vibrational-rotational study of the electronic ground state of the hydrogen molecule. J. Chem. Phys., 45 515, 1966. 

Most known chemical lasers oscillate on vibration-rotation transitions of a hydrogen halide. The first such laser was driven by the flash initiated explosion of H2 + C12 mixtures287. Here the flash dissociates the Cl2 to start the chain decomposition, and the population inversion is due to the subsequent reactions... 

In this section we have concentrated on calculations for H-T only, which have particular relevance to the fine and hyperfine constants determined from Jefferts experiments. Many other papers deal with calculations of the vibration-rotation level energies, for which there is much less experimental data. There are also many papers dealing with the heteronuclear molecule, HD+, which is really a special case because the Bom Oppenheimer approximation collapses, particularly for the highest vibrational levels of the ground electronic state. Even the homonuclear species H and D exhibit some fascinating and unusual effects in their near-dissociation vibration rotation levels. Finally we note that in order to match the accuracy of the experimental measurements for all the hydrogen molecular ion isotopomers, it is necessary to include radiative and relativistic effects. 

For those cases in which one of the colliding partners is molecular hydrogen or deuterium, the classical rotator approximation is particularly poor. One then anticipates efficient vibration-rotation exchange only when the rotational level spacings are such that the energy defects are relatively small. For such a gas at temperature T, it is also necessary to consider the population of the particular initial rotational state that can participate efficiently in the energy... 

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