Waldemar Głaz

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 Deltabeta(R). A method for the computation of the spherical, rotationally adapted components Deltabeta(lambdaL) ((s,K))(R) of Deltabeta(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 Schrodinger 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.

The hyper-Rayleigh light scattering spectrum of gaseous Ne–Ar mixture

Hyper-Rayleigh binary collisional spectra for a Ne–Ar gaseous system are computed within the frequency range up to 500 cm−1 with four new ab initio hyperpolarizability models used. The properties of the profiles as well as the depolarization ratio frequency dependence are discussed. The contributions to the spectra given by the dipolar b1(r) and the octopolar b3(r) components of the hyperpolarizability tensor and the multipolar model HR spectrum are compared.

Binary rototranslational hyper-Rayleigh spectra of H2–He gas mixture

The collision-induced rototranslational hyper-Rayleigh spectra of gaseous H(2)-He mixture are computed and discussed in the binary regime. As the input data we use our ab initio computed H(2)-He collision-induced first dipole hyperpolarizability tensor Deltabeta(R). Both the vector and the septor part of the H(2)-He hyper-Rayleigh spectra are evaluated at room temperature (T=295 K). The spectra are calculated assuming the full quantum computations based on the Schrödinger equation of the relative translational motion in the isotropic H(2)-He potential as well as using semiclassical methods.

Hyper-Rayleigh spectral intensities of gaseous Kr-Xe mixture.

Binary collision-induced hyper-Rayleigh (CIHR) spectra of Kr-Xe gaseous system are computed quantum mechanically and classically within the frequency range up to 380 cm(-1). The intensities are expressed in absolute units. The details of the theory developed for the CIHR spectra are given and the properties of the profiles as well as the depolarization ratio frequency dependence are discussed. The contributions to the spectra related to the vector b10(r) and the septor b30(r) components of the hyperpolarizability tensor are evaluated.

Intermolecular polarizabilities in H2-rare-gas mixtures (H2–He, Ne, Ar, Kr, Xe): Insight from collisional isotropic spectral properties

The report presents results of theoretical and numerical analysis of the electrical properties related to the isotropic part of the polarizability induced by interactions within compounds built up of a hydrogen H2 molecule and a set of noble gas atoms, Rg, ranging from the least massive helium up to the heaviest xenon perturber. The Cartesian components of the collisional polarizabilities of the H2-Rg systems are found by means of the quantum chemistry methods and their dependence on the intermolecular distance is determined. On the basis of these data, the spherical, symmetry adapted components of the trace polarizability are derived in order to provide data sets that are convenient for evaluating collisional spectral profiles of the isotropic polarized part of light scattered by the H2-Rg mixtures. Three independent methods of numerical computing of the spectral intensities are applied at room temperature (295 K). The properties of the roto-translational profiles obtained are discussed in order to determine the role played by contributions corresponding to each of the symmetry adapted parts of the trace polarizability. By spreading the analysis over the collection of the H2-Rg systems, evolution of the spectral properties with the growing masses of the supermolecular compounds can be observed.

Moments of hyper-Rayleigh spectra of selected rare gas mixtures

In this work we have analyzed spectral moments characterizing properties of the collisionally hyper-Rayleigh scattered light. This is a supplementary study undertaken in order to complete the series of our previously published papers on the collisional hyper-Rayleigh scattering spectral profiles. In order to evaluate the moments we have extended the theory so that it could embrace the (hyper)polarizabilities of higher rank. Using the expressions developed on the grounds of the theoretical principles and applying appropriate computational methods with ab initio hyperpolarizability values as an input, we have obtained desirable moment values for three diatomic noble gas systems: HeNe, HeAr, and NeAr, at several temperature points. The semiclassical and the quantum treatments have been taken into account, and the moments were calculated both from the sum rule method as well as from the spectral profiles. The results were compared and discussed.

Effects of anisotropic interaction-induced properties of hydrogen-rare gas compounds on rototranslational Raman scattering spectra: Comprehensive theoretical and numerical analysis

A comprehensive study is presented of many aspects of the depolarized anisotropic collision induced (CI) component of light scattered by weakly bound compounds composed of a dihydrogen molecule and a rare gas (Rg) atom, H2-Rg. The work continues a series of earlier projects marking the revival of interest in linear light scattering following the development of new highly advanced tools of quantum chemistry and other theoretical, computational, and experimental means of spectral analyses. Sophisticated ab initio computing procedures are applied in order to obtain the anisotropic polarizability components dependence on the H2-Rg geometry. These data are then used to evaluate the CI spectral lines for all types of Rg atoms ranging from He to Xe (Rn excluded). Evolution of the properties of CI spectra with growing polarizability/masses of the complexes studied is observed. Special attention is given to the heaviest, Kr and Xe based, scatterers. The influence of specific factors shaping the spectral lines (e.g., bound and metastable contribution, potential anisotropy) is discussed. Also the share of pressure broadened allowed rotational transitions in the overall spectral profile is taken into account and the extent to which it is separable from the pure CI contribution is discussed. We finish with a brief comparison between the obtained results and available experimental data.

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 collisional light scattering. Theoretical versus ab initio hyperpolarizability models.

Collision-Induced hyper-Rayleigh light scattering (CIHRS) on super-molecular compounds composed of lighter noble gas atoms (He, Ne and Ar) and linear hydrogen molecules has been recently discussed within theoretical as well as numerical comparative spectral studies. The aim of the present report is to analyze updated results in this field of inter est generalized over the case of two heavier units of H2Kr and H2Xe. The roto-translational collisional profiles are obtained by means of quantum mechanical and semi-classical calculations. Tensorial symmetry adapted components of the first hyperpolarizability, Δβ – responsible for occurrence of the CIHRS processes – are applied on the grounds of previously calculated Cartesian quantities, found by means of the quantum chemistry (ab initio) methods. The spectral lines evaluated are partially treated as a benchmarking device to estimate the importance of the long-distance Δβ(R) dependence determined on the basis of the theoretical multipole-induced-multipole analytical model. Moreover, the magnitude of the CIHRS effect is discussed in regard to the experimental feasibility of CIHRS detection.

Spatial dependence of hyperpoarizabilty of van der Waals supermolecule H_2-Ne. Its influence on spectral properties of hyper-Rayleigh collisionally scattered light

A series of reports has been published previously for several last years on the nonlinear hyper-Rayleigh (HR) collisional light scattering in molecular media composed of interacting atomic and atomic-diatomic compounds. The presented study continues and extends these theoretical and numerical analyses. Especially, a careful insight into the spectral properties of the most recent case considered - the HR scattering in H2-Ne gas mixtures -is given by calculating and examining a complete set of spectral line contributions related to symmetry adapted (SA) components of the collisional first hyperpolarizability tensor ΔβΛL(K). The influence of the ΔβΛL(K)(R) functional behavior on the HR spectral line shapes is found and characterized in details. A possibility of estimating numerical values of the SA contributions is discussed. Moreover, the long distance functional dependencies of Δβ(R), obtained by means of the numerical quantum chemistry methods, are confronted with those derived on the basis of an analytical approach within the molecular interaction models proposed at the early stage of development of the collisional nonlinear spectroscopy by Kielich and coworkers.