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

Hyper-Rayleigh spectral intensities of gaseous Kr–Xe mixture

Binary collision-induced hyper-Rayleigh s CIHR d 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

Endoscopic Appearance of the Gastroesophageal Valve and Competence of the Cardia

The endoscopic appearance of the gastroesophageal valve, viewed by the retroflexed gastroscope, has been studied in 51 patients with and without reflux esophagitis. Esophagitis was graded according to its severity, and the yield pressure (YP) was measured in all patients to assess the competence of the cardia. There was a close relationship between the YP and the grades of the gastroesophageal valve. YP was significantly lower in patients with endoscopic oesophagitis than in patients with no evidence of reflux esophagitis (p <0.0001). An increased abnormality of the gastroesophageal valve was associated with all grades of esophagitis and with a low YP. The valve mechanism at the cardia has an important role in determining its competence. YP is possibly a measure of the flap valve component of the gastroesophageal junction

High order polarizabilities from optical interaction-induced Spectroscopy

Multipolar polarizability contributions to the collision-induced light scattering spectra of optically isotropic molecules may be put in evidence in the Rayleigh wings and in the vicinities of the v1 Raman vibrational lines. Experiments on CH4 or CF4 (tetrahedral symmetry) and SF6 (octahedral symmetry) make possible evaluations of the multipolar polarizabilities provided that isotropic Rayleigh spectra and anisotropic Raman bands are obtained in some relatively large frequency ranges. These evaluations — in particular those based on set inversion analysis — constitute experimental references for quantum chemistry computations of the multipolar polarizabilities. In the case of CH4, CF4 and SF6, the agreement between experimental and ab initio values is quite good

Multipolar polarizabilities from interaction-induced Raman scattering

In this chapter the authors first give a general presentation of collision-induced scattering (CIS), also named interaction induced scattering. The different types of molecular interaction are mentioned, with a special emphasis on the multipolar polarizabilities contributions studied in the authors\u27 laboratories since the beginning of 1990s. The authors describe the setup and the experimental procedure used for the measurement of the scattering on an absolute scale. They also discuss the multipolar contributions to depolarized and isotropic CIS for specific molecular symmetries. Studies in the Rayleigh wings of isotropic molecules such as CF4 and SF6 and of linear molecules such as N2 and CO2 are presented. The authors also report on observations made in the wings of vibrational Raman bands of CF4 and SF6

Collision-induced scattering in CO2 gas

Carbon‐dioxide gas rototranslational scattering has been measured at 294.5 K in the frequency range 10–1000 cm−1 at 23 amagat. The depolarization ratio of scattered intensities in the frequency range 10–1000 cm−1 is recorded. The theoretical and experimental spectra in the frequency range 10–470 cm−1 are compared. The anisotropic double differential cross section for scattered light is calculated theoretically considering first‐ and second‐order dipole‐induced dipole, first‐order dipole–induced octopole, and first‐order dipole–dipole–quadrupole light scattering mechanisms as well as their cross contributions

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