Showing papers on "Hyperpolarizability published in 1984"

Chirality and hydrogen bonding in molecular crystals for phase‐matched second‐harmonic generation: N‐(4‐nitrophenyl)‐(L)‐prolinol (NPP)

Abstract: The higher second‐harmonic efficiency, in powder, of a new organic molecular crystal N‐(4‐nitrophenyl)‐(L)‐prolinol (NPP) is reported. Electronic polarizability of NPP molecules relates to that of other para‐nitroaniline‐like structures such as that of previously reported N‐(2,4‐dinitrophenyl) methyl alaninate (MAP), and the increase in crystalline nonlinear efficiency by one order of magnitude above the latter is ascribed to an ‘‘optimized’’ crystalline structure rather than to minor changes of the molecular hyperpolarizability. The simultaneous chiral and hydrogen‐bonding character of the prolinol electron‐donating group leads to a quasioptimal angle, with respect to quadratic phase‐matched nonlinear interactions, between the molecular transition dipole moments and the twofold axis of the monoclinic P21 crystal structure. Based on a simple oriented gas description of the quasiplanar structure of the crystal, two possible mutually exclusive second‐harmonic phase‐matched configurations are evidenced and s...

An ab initio study of the non-linear optical properties of the He atom and the H2 molecule

Abstract: Using the steady state formulation of the time-dependent Schrodinger equation a systematic examination has been undertaken of the frequency dependent dipole polarizabilities and third order susceptibilities for the helium atom and the hydrogen molecule. Full configuration interaction wavefunctions determined using large basis sets were employed. For both systems the calculated dipole polarizabilities are in excellent agreement with the best known results. For the calculated non-linear susceptibilities-the frequency dependent hyperpolarizability and the coefficient of the third harmonic generation-the results are estimated to be accurate to within a few per cent.

Higher order collision induced Raman scattering from the dipole forbidden v 9 mode of ethane

Abstract: The interaction induced v 9 signal from ethane has been observed by conventional Raman techniques. This mode is formally forbidden by the dipole-polarizability selection rules, but can be activated by higher order hyperpolarizability and/or quadrupole polarizability mechanism. Ethane was studied under four temperature and seven reduced density conditions. From these experimental results the specific multipole mechanism giving rise to v 9s activity has been determined. The appearance of a three body, R 3, term has been observed and its spherical tensor rank has been determined. The data have been interpreted by means of Buckingham's multipole expansion model.

Intensities in vibrational hyper-Raman spectra. A bond hyperpolarizability theory

Abstract: On presente une theorie de l'hyperpolarisabilite de liaison qui permet d'exprimer le tenseur d'hyperpolarisabilite moleculaire en fonction de l'hyperpolarisabilite des liaisons et des coefficients definissant les coordonnees normales de vibration

Theory and computational methods for studies of nonlinear phenomena in laser spectroscopy. II. Calculations of steady‐state wave functions

Abstract: Methods will be developed for variational calculations of steady-state wave functions and the corresponding quasienergies. These functions appear as solutions to the time-dependent Schrodinger equation for a molecule interacting with an oscillating electromagnetic field. A variation principle is used to obtain coupled equations for each Fourier component (FC) of the steady-state wave function. The FCs are expanded in configuration state functions using the structure of the complete active space (CAS) SCF approach. Two methods are outlined, one which is based on a common set of molecular orbitals for all FCs and one based on an individual optimization of both CI coefficients and molecular orbitals for each FC. The latter method leads to molecular orbital sets for the different FCs which are mutually nonorthogonal. Formulas are derived for the calculation of higher-order dynamic susceptibilities for steady states. An application is made to the H2 molecule, and results are presented for the frequency-dependent polarizability and hyperpolarizability along the molecular axis. The static values obtained are α = 6.413 (6.387) and γ = 676 (674) atomic units, with exact numbers within parentheses.

Surface polarization induced by an adatom in a dielectric

Abstract: The electric polarization induced inside a solid and close to its surface by the presence of an adatom is studied in the absence of electron overlap. It varies as the inverse fourth power of the distance between the atom and the surface and depends on the linear polarizability of the atom and on the quadratic (electro‐optical) hyperpolarizability for a unit volume of the solid. The result is shown to be consistent with the formulation of other, related van der Waals polarization effects presently available in the literature.