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

Collisional ab initio hyperpolarizabilities in computing hyper-Rayleigh spectra of noble gas heterodiatomics

We review some recent studies on the theoretical and computational aspects of collision-induced nonlinear properties and phenomena, such as: the first hyperpolarizability of inert gas heteroatomic pairs (He-Ne, He-Ar, N-Ar and Kr-Xe) and spectral properties of hyper-Rayleigh scattered light in such systems. The hyperpolarizability data obtained by means of a variety of methods of quantum chemistry were applied to calculate spectral HR profiles. Computations are performed both quantum-mechanically and classically for two temperature values T=95 K and T:295 K. Resulting tensorial properties and spectra are presented and discussed

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 Δ β ( 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

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 (H 2 ) 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

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

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

Cartesian components of the collision-induced (CI) hyperpolarizability Δβ tensor are computed for the linear, T-shaped, and 45∘ configurations of the H2-Ne pair in the intermolecular range 3 to 14 bohr. Symmetry-adapted components Δβ(K)λ L(R) of the vector (K=1) part, as well as the septor (K=3) part, of the H2-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 H2-Ne binary gas mixture are determined in the frequency range from −1250 to 2500 cm−1. The profiles are partially employed as a benchmarking device to estimate the importance of the short intermolecular distance part of the Δβ(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

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

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 component’s 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

On the potential application of DFT methods in predicting the interaction-induced electric properties of molecular complexes. Molecular H-bonded chains as a case of study

A detailed analysis of the selected DFT functionals for the calculations of interaction-induced dipole moment, polarizability and first-order hyperpolarizability has been carried out. The hydrogen-bonded model chains consisting of HF, H2CO and H3N molecules have been chosen as a case study. The calculations of the components of the static electric properties using the diffuse Dunning’s basis set (aug-cc-pVDZ) have been performed employing different types of density functionals (B3LYP, LC-BLYP, PBE0, M06-2X and CAM-B3LYP). Obtained results have been compared with those gained at the CCSD(T) level of theory. The counterpoise correction scheme, namely site-site function counterpoise, has been applied in order to eliminate basis set superposition error. The performed tests allow to conclude that the DFT functionals can provide a useful tool for prediction of the interaction-induced electric properties, however a caution has to be urged to their decomposition to the two- and many-body terms