Author: Paul G. GillardPublisher:
ISBN:
Category : Deuterium
Languages : en
Pages : 290
Book Description
Aspects of Collision-induced Absorption of Hydrogen and Deuterium
Author: Paul G. GillardPublisher:
ISBN:
Category : Deuterium
Languages : en
Pages : 290
Book Description
Aspects of Collision-induced Absorption of Hydrogen and Deuterium
Author: Paul G. GillardPublisher:
ISBN:
Category : Deuterium
Languages : en
Pages : 0
Book Description
Collision-induced Absorption of Hydrogen Containing Systems
Author: Hua-Kuang LeePublisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 99
Book Description
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.
Collision-induced Absorption of the First Overtone Bands of H2 and
Author: Mahmoud Hasan Abu-KharmaPublisher:
ISBN:
Category : Absorption spectra
Languages : en
Pages : 238
Book Description
Collision-induced Absorption by Molecular Deuterium (D2) in the Rototranslational Band, the Fundamental Band, and the First Overtone Band of
Author: Martin Andreas AbelPublisher:
ISBN:
Category :
Languages : en
Pages : 264
Book Description
The electric charge distribution of molecules such as H2 and D2 is inversion-symmetric so that permanent dipole moments do not exist: such molecules are infrared-inactive. It is therefore interesting that gaseous, liquid, and solid hydrogen and its isotopes actually absorb infrared radiation, for example if gas densities are sufficiently high. The observed absorption arises from electric dipole moments induced by intermolecular interactions. It is of a supermolecular origin, due to binary (or higher-order) molecular complexes that may be transient (i.e., in a collisional encounter) or relatively stable (van-der-Waals molecule). Interaction-induced electric dipoles arise from the same mechanisms that generate the intermolecular forces: exchange forces, dispersion forces, and multipolar induction. Recently the induced dipole and potential energy surfaces of H2 pairs have been obtained by advanced quantum-chemical calculations. Interaction-induced absorption, more commonly called collision-induced absorption (CIA), by H2 pairs is an important opacity source in the atmospheres of various types of planets and cool stars, such as late stars, low-mass stars, brown dwarfs, certain white dwarfs, etc., and therefore of special astronomical interest. The emission spectra of cool white dwarf stars differ significantly from the expected blackbody spectra of their cores, mainly due to collision-induced absorption by collisional complexes of hydrogen and helium in the stellar atmospheres. Before proceeding to the frequencies and temperatures of interest it is good to check the new potential energy surface and induced dipole surface in all possible ways by comparison with existing isotopic laboratory measurements. Furthermore, the new potential energy surface is directly compared with previously available, well established intermolecular potential energy surfaces. The electric charge distributions of deuterium and hydrogen are very similar. The new potential energy and induced dipole surfaces were originally obtained to facilitate the computation of the collision-induced absorption of hydrogen. However, by replacing the rotovibrational wavefunctions of H2 with those of D2 the surfaces can also be used to calculate the collision-induced absorption of deuterium pairs, thereby probing them further. At the temperature of 298K existing measurements of the collision-induced absorption of D2--D2 gas are compared with our quantum scattering calculations in the D2 fundamental band (approximately 2,500cm−1 to 4,500cm−1). Furthermore, measurements of the collision-induced absorption of deuterium (D2) in the D2 first overtone band (about 5,250cm−1 to 7,250cm−1) at 201K are reported. These measurements are compared with ab initio calculations of the absorption spectra. Close agreement of measured and calculated spectra is seen.
Collision-induced Absorption in Gases
Author: Lothar FrommholdPublisher:
ISBN: 9780521393454
Category : Science
Languages : en
Pages : 410
Book Description
This book reviews the theory and experiment of collision-induced absorption of infrared radiation in dense gases.
Collision-induced absorption of nitrogen-methane and hydrogen-methane pairs
Author: Michael BuserDensity Effects in the Collision-induced Absorption Spectra of Molecular Hydrogen
Author: James P. A. YoudenPublisher:
ISBN:
Category : Hydrogen
Languages : en
Pages : 43
Book Description
NASA Technical Note
Author: Calculated Pressure-induced Vibrational Absorption in H2 - H2 Collisions in Hydrogen Gas
Author: R. W. PatchPublisher:
ISBN:
Category : Absorption
Languages : en
Pages : 52
Book Description