Collision-induced hyper-Rayleigh spectrum of H2–Ar gas mixture

The collision-induced hyper-Rayleigh (CIHR) spectra of the gaseous H 2 – Ar mixture are discussed in the binary regime on the basis of our ab initio computed H 2 – Ar collision-induced (CI) first dipole hyperpolarizability tensor Δ β ( R ) . A method for the computation of the spherical, rotationally adapted components Δ β λ L ( s , K ) ( R ) of Δ β ( R ) needed for spectroscopic line shape analysis is proposed. Both the vector and the septor parts of the H 2 – Ar CIHR spectrum are evaluated at room ( T = 295 K ) temperature. The spectra are calculated assuming the full quantum computations based on the Schrödinger equation of the relative translational motion of H 2 – Ar as well as semiclassical methods (classical trajectory approach and Birnbaum–Cohen model translational profiles). The H 2 – Ar pair CIHR septor spectrum has been found stronger than the vector one

Ambient Atmospheric Hydrocarbon Content as Determined by Gas Chromatographic Techniques from Rural Tidewater Virginia in Late Spring 1974

In an attempt to ascertain the naturally generated hydrocarbon contribution to the air quality of the Hampton Roads region of Tidewater Virginia, a series of 27 air samples was obtained in two rural locations during late spring of 1974. These samples were analyzed for their hydrocarbon content (carbon number range C5 to C10) using gas chromatographic techniques. The thirty different hydrocarbon species were identified and monitored in the experiment. Preliminary analysis of the data indicates an average concentration of 397 parts per billion by weight (carbon) for the total non-methane hydrocarbon loading for C5 to C10 during the experiment. This value exceeds the National Primary Air Quality Standards as set by the Environmental Protection Agency

Multi-property isotropic intermolecular potentials and predicted spectral lineshapes of collision-induced absorption (CIA), collision-induced light scattering (CILS) and collision-induced hyper-Rayleigh scattering (CIHR) for H2 –Ne, −Kr and −Xe

Quantum mechanical lineshapes of collision-induced absorption (CIA), collision-induced light scattering (CILS) and collision-induced hyper-Rayleigh scattering (CIHR) at room temperature (295 K) are computed for gaseous mixtures of molecular hydrogen with neon, krypton and xenon. The induced spectra are detected using theoretical values for induced dipole moment, pair-polarizability trace and anisotropy, hyper-polarizability and updated intermolecular potentials. Good agreement is observed for all spectra when the literature and the present potentials which are constructed from the transport and thermo-physical properties are used

Collision-induced hyperpolarizability and hyper-Rayleigh spectra in the He–Ar heterodiatom

The ab initio interatomic distance dependent collision induced dipole moment, polarizability and the vector b1 (R) and an irreducible 3rd rank tensor b3 (R) components of the first hyperpolarizability tensor b of He–Ar pair are obtained. The hyperpolarizability data are applied in order to calculate the collision induced He–Ar hyper-Rayleigh spectra both quantum-mechanically and semiclassically for the frequency shifts up to 1200 cm-1. Computations were carried out for two temperature values – T = 295 K and T = 95 K. Spectral features of both vector and the irreducible 3rd rank tensor parts of CIHR spectra are analyzed. The frequency dependent behavior of the HR depolarization ratio is discussed

Modeling of Hydrogen Storage Materials: A Reactive Force Field for NaH

Parameterization of a reactive force field for NaH is done using ab initio derived data. The parameterized force field(ReaxFFNaH) is used to study the dynamics governing hydrogen desorption in NaH. During the abstraction process of surface molecular hydrogen charge transfer is found to be well described by the parameterized force field. To gain more insight into the mechanism governing structural transformation of NaH during thermal decomposition a heating run in a molecular dynamics simulation is done. The result shows that a clear signature of hydrogen desorption is the fall in potential energy surface during heating

Second Harmonic Elastic Light Scattering by Gases Composed of Centrosymmetric Molecules. The Case of H2‐Ar.

A numerical and theoretical study of nonlinear collisional electrical and/or optical properties of near van der Waals weakly bound complexes is presented. The molecular systems considered are composed of a linear nonpolar molecule ( H 2 taken as an example) and a spherical atomic entity (Ar)—a supermolecule of symmetry of one step lower than that considered before. The basic stage of the procedure developed consists of computational quantum chemistry efforts of determining values of the first hyperpolarizability tensor for several intermolecular configuration arrangements. Subsequent theoretical discussion includes these quantities within a routine developed in order to produce symmetry adapted (SA) components of the hyperpolarizability tensor, which are finally used so that the spectral distributions of the collision‐induced hyper‐Rayleigh (CIHR) light scattering could be determined. Translational parts of these functions have served as an assessment tool to judge about the role played by a particular SA contribution in the overall tensorial property. In particular, the convergence of the series expansion of the hyperpolarizability dependence on intermolecular distances has been investigated. Three computational methods based on quantum and semiclassical approach have been compared

Morphology of collisional nonlinear spectra in H2-Kr and H2-Xe mixtures

This article reports new results of theoretical and numerical studies of spectral features of the collision-induced hyper-Rayleigh light scattered in dihydrogen-noble gas (H2 -Rg) mixtures. The most massive and polarizable scattering supermolecules with Rg = Kr and Xe have been added to the previously considered systems in order to gain a more complete insight into the evolution of the spectral properties. The symmetry adapted components of the first collisional hyperpolarizabilities are obtained by means of the quantum chemistry numerical routines supplemented with appropriate theoretical methods. Roto-translational spectral lines are calculated on the grounds of the quantum-mechanical as well as semi-classical approach. The role of particular hyperpolarizability components in forming the line shapes is discussed. The intensities of the lines are compared with those obtained for less massive scatterers. Advantages of prospective application of the new scattering systems for experimental detection of the nonlinear collisional effects are indicated

Hyper-Rayleigh light-scattering spectra determined by ab initio collisional hyperpolarizabilities of He-Ne atomic pairs

The collision-induced CI first hyperpolarizability tensor for the He-Ne pair composed of the lightest noble gas elements has been obtained on the grounds of an ab initio method as a function of the interatomic distance R. Collision-induced hyper-Rayleigh CIHR spectra scattered in mixtures of such atoms at temperatures of 95 and 295 K are computed in absolute units both quantum mechanically and classically for the frequency shifts up to 1000 cm−1. The spectral features of the CIHR profiles due to the vector b1 and septor b3 parts of the hyperpolarizability tensor are discussed. The quantum character of computed spectra, especially significant at lower temperatures, has been found out. The integrated intensities of the spectra have been evaluated and used as a criterion of the reliability of the computed profiles. The frequency-dependent depolarization ratio of the CIHR spectra was evaluated and discussed. The properties of the resulting HR profiles have been compared with the depolarized CI Rayleigh spectrum of the He-Ne pair