In the Big Bang, hydrogen and helium were produced, with very small quantities of deuterium, tritium, and lithium. Due to gravitational attraction, the gases began to congregate. The conversion of gravitational potential energy to kinetic energy raised the temperature. For the gas clouds to continue to contract for form stars, some cooling mechanism was needed. In this thesis, ab initio calculations of collision-induced dipoles are reported, for use in evaluating collision-induced emission as a potential cooling mechanism during the formation of the first stars. In nonequilibrium conditions, molecular hydrogen and atomic hydrogen can coexist, so transient dipoles formed during collisions of molecular hydrogen with either molecular hydrogen or atomic hydrogen may contribute to cooling. The first stars that were formed in the universe are called Population III stars. This thesis includes calculations that are relevant to the observed radiative profiles of very old, very cool white dwarf stars. The detected radiation from the stars is a combination of the radiation from both the core and the stellar atmosphere. Radiation coming from the core may be absorbed by the atmosphere and then reemitted at a lower frequency. The core temperature and the radiative spectrum from the core can be evaluated by fitting the high-energy end of the spectrum with a black-body radiative profile. Often the radiative profile at lower energy does not fit the predicted profile, based on the core temperature. This is attributed to absorption in the stellar atmosphere, due to transient dipoles formed during collisions of hydrogen molecules with hydrogen atoms, helium atoms, or other hydrogen molecules.Due to the harsh conditions that are required for the existence of atomic hydrogen, experimental data collision-induced absorption involving atomic hydrogen is not available from experiment. Also, results at very high temperatures are not available from experiment. The collision-induced dipoles and collision-induced absorption spectra must be determined through computational work. The interest in atomic hydrogen for the astrophysical applications leads to the three research projects that are described in this thesis: 1) the dipole moment of the H2-H system in various configurations, 2) the energy and dipole moment of equilateral/isosceles triangular H3, and 3) the correlation energy and dipole of He-H.This thesis contains high-level ab initio computational results for all three projects, obtained with comparatively large basis sets. The results for H2-H are the best available. The collision-induced dipole has been expressed as a series in the spherical harmonics of the H2 bond vector and the intermolecular vector for various bond lengths and intermolecular separations. The calculated coefficients in this series are reported, and it is shown that the coefficients converge to the known analytical forms at long range. For H3, the energies of the three lowest states are reported as functions of the H-H separation and vertex angle in equilateral and isosceles triangular configurations. The conical intersection is located. For He-H, the calculated correlation energies and the correlation contribution to the dipole are shown to match the known long-range forms very accurately. The leading sp-charge density matrix on H shows the predicted R7 behavior. It appears that larger basis sets are required to show the same behavior at the He center.
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