Anastasios Haskopoulos

Interaction induced (hyper)polarizability in Ne Ar

Abstract We report interaction dipole moment and (hyper)polarizability calculations for the NeAr diatom. Our values are extracted from finite-field Moller–Plesset, coupled cluster and density functional theory calculations. At an internuclear separation of 6.5 a 0 , very near the equilibrium of this system, CCSD(T) calculations with a [7s5p4d1f/8s6p5d3f] basis set yield the following interaction properties: dipole moment, μ int =0.0022 ea 0 , mean and anisotropy of the dipole polarizability, α int =−0.02 and Δα int =0.59 e 2 a 0 2 E h −1 , mean and anisotropy of the first dipole hyperpolarizability, β int =2.0 and Δβ int =0.1 e 3 a 0 3 E h −2 . The B3LYP method provides a reasonable description of the interaction properties of NeAr.

Interaction induced dipole moment and polarizability in CO2⋯Rg, Rg=He, Ne, Ar, Kr and Xe

Abstract We have obtained interaction induced dipole moments and polarizabilities for CO2⋯Rg, Rg=He, Ne, Ar, Kr and Xe. Relying on Moller–Plesset perturbation theory and coupled cluster calculations with large, especially designed basis sets we have collected pertinent observations on various computational aspects characteristic of these systems. For the most stable T-shaped configuration of CO2⋯Rg the interaction dipole moment μint/ea0 evolves as 0.0063 (He), 0.0107 (Ne), 0.0281 (Ar), 0.0345 (Kr), 0.0398 (Xe) and the mean polarizability α int /e 2 a 0 2 E h −1 as −0.0494 (He), −0.0897 (Ne), −0.2752 (Ar), −0.3744 (Kr), −0.5111 (Xe).

Interaction Electric Hyperpolarizability Effects in Weakly Bound H2O···Rg (Rg = He, Ne, Ar, Kr and Xe) Complexes†

We report an extensive high-level ab initio theoretical investigation of the interaction electric properties of the weakly bound complexes of water with rare gases, H(2)O...Rg (Rg = He, Ne, Ar, Kr and Xe). Our approach relies on finite-field many-body perturbation theory (MP) and coupled-cluster (CC) calculations with flexible, carefully designed basis sets of Gaussian-type functions (GTFs). We have obtained estimates of the electron correlation effects on the reference self-consistent field (SCF) values at all levels of theory employed in this work. For the planar equilibrium configuration (C(s) symmetry) of the complexes, at the CCSD(T) level of theory, the interaction mean first hyperpolarizability is positive (SCF values in parentheses): beta(int)/e(3)a(0)(3)E(h)(-2)(H(2)O-Rg) = 0.72 (0.56), 1.20 (0.79), 7.04 (4.28), 9.88 (5.34), and 15.52 (6.68) for Rg = He, Ne, Ar, Kr, and Xe, respectively. For the interaction mean second hyperpolarizability, we have obtained (SCF values in parentheses): gamma(int)/e(4)a(0)(4)E(h)(-3)(H(2)O-Rg) = -18.93 (-14.19), -37.78 (-24.35), -83.16 (-72.42), -102.92 (-125.70), and -206.45 (-286.83) for Rg = He, Ne, Ar, Kr, and Xe. In addition to the equilibrium values of the interaction electric properties, we have also extracted information for their dependence on the variation of the distance of the rare gas atom from the center of mass of the water molecule (without changing direction). The gradient of the interaction mean second hyperpolarizability at the equilibrium configuration is determined as (dgamma(int)/dR)(e)/e(4)a(0)(3)E(h)(-3)(H(2)O-Rg) = 9.89 (He), 25.42 (Ne), 73.71 (Ar), 144.71 (Kr), and 324.68 (Xe).

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.

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.

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.

Nonlinear properties and collisional spectra in hydrogen-(heavy) noble-gas-atom mixtures

In a series of previously published works the phenomenon of collision induced nonlinear hyper-Rayleigh scattering of light (CIHRS) was studied on the basis of the numerical quantum chemistry (QC) methods confronted with a theoretical approach. A class of super-molecular systems composed of hydrogen (H2) and lighter inert gas atoms (Rg) was considered. In this report a development of this research work is presented with more massive and highly polarizable, Kr and Xe, perturbers involved. The collision-induced hyperpolarizability tensorial values, Δβ obtained by means of the QC ab initio methods are applied in order to produce the CIHRS spectral distributions; the influence of Δβ features on the line shapes is compared with the earlier theoretical predictions. Namely, the validity of the multipole-induced-multipole (MIM) mechanism is assessed. In particular, its relevance to reproduce long-range functional behavior of the so-called symmetry adapted (SA) components of the hyperpolarizability tensor Δβ(R) is discussed. A thorough analysis of the translational CIHRS spectra is then performed to identify the role of the hyperpolarizability spatial distribution in forming particular sections of the line shapes. An extension of the dipole-induced-quadrupole analytical model is suggested and tested with regard to its ability to reproduce more accurate profiles.

Collision-induced hyper-Rayleigh light scattering in gaseous dihydrogen-neon mixtures

Cartesian components of the collision-induced (CI) hyperpolarizability {Delta}{beta} tensor are computed for the linear, T-shaped, and 45 deg. configurations of the H{sub 2}-Ne pair in the intermolecular range 3 to 14 bohr. Symmetry-adapted components {Delta}{beta}{sub {lambda}L}{sup (K)}(R) of the vector (K=1) part, as well as the septor (K=3) part, of the H{sub 2}-Ne CI hyperpolarizability are calculated starting from the ab initio Cartesian hyperpolarizability tensor values transformed into their spherical counterparts. By applying these quantities, the vector together with the septor collision-induced hyper-Rayleigh (CIHR) spectra for the H{sub 2}-Ne binary gas mixture are determined in the frequency range from -1250 to 2500 cm{sup -1}. The profiles are partially employed as a benchmarking device to estimate the importance of the short intermolecular distance part of the {Delta}{beta}(R) dependence. The depolarization ratio of the CIHR spectra in the whole frequency range is also calculated. The nature of the CIHR signal and the feasibility of the related experiments are discussed and analyzed.