Radiative quenching and excitation of metastable states upon differential scattering of atoms: II. The He(1<Superscript>1</Superscript><Emphasis Type="Italic">S</Emphasis>–2<Superscript>1</Superscript><Emphasis Type="Italic">S</Emphasis>)-Ne molecule

The differential cross sections of radiative-collisional quenching (absorption) of a metastable state of a colliding atom are calculated for the first time. As a particular example, the reaction of quenching (excitation) of the metastable state He(2¹S) in collisions with Ne atoms in the ground state is considered. The calculations are performed for the thermal collisional energy E = 10^?3 au for a wide range of radiation frequencies, including both wings and the center of the line of a forbidden atomic transition, and are based on the uniform quasi-classical approximation, which generalizes the Franck-Condon approximation to the case of an exponential dependence of the transition dipole moment on the internuclear distance, as well as to the case of nonintersecting terms. The calculated differential cross sections have an oscillating structure, which, for the blue wing of the forbidden spectral line, is interpreted as Stückelberg oscillations. At a radiation frequency close to the frequency of the forbidden atomic transition, a sharp maximum in the differential cross section—the giant glory effect—is observed in the range of small scattering angles. This effect is shown to occur as a result of superimposition of the rainbowlike feature of the differential cross section on the glory feature.     

Collision of Rydberg atom A** with atom B in the ground electronic state. Optical potential

A method for calculating the complex optical potential of slowly colliding Rydberg atom A^** and neutral atom B in the ground electronic state is suggested. The method is based on the asymptotic approach and the theory of multichannel quantum defects, which uses the formalism of renormalized Lippmann-Schwinger equations. The potential is introduced as the 〈q|V _opt|q〉 matrix element of the optical interaction operator, for which the integral equation is derived, and is calculated in the basis set of free particle wave functions |q〉. Fairly simple equations for the shift and broadening of the ionic term are obtained, and the principal characteristics of these equations are analyzed. By way of illustration, the optical potential of the Na^**(nl)+B systems, where B is a rare gas atom, is calculated.     

A program set for finding structure-property correlations using topological indices

Moscow State University. Translated from Zhurnal Strukturnoi Khimii, Vol. 30, No. 6, pp. 145–147, November–December, 1989.     

Discontinuity of dipole-moment matrix elements in ellipsoidally shaped nanoparticles and profiles of spectral lines

The behaviour of energy levels and optical spectra of a charged particle (electron or hole) confined within a potential well of ellipsoidal shape is investigated as a function of the shape-anisotropy parameter. If two energy levels of the same symmetry intersect in a perturbation-theory approximation, they move apart on direct diagonalization of the appropriate Hamiltonian. The intersection of the energy levels leads to a discontinuity of the corresponding dipole-moment matrix element. The discontinuity of matrix elements is not reflected in the behaviour of transition probabilities which are continuous functions of the shape-anisotropy parameter. The profiles of a spectral line emitted or absorbed by an ensemble of ellipsoidally shaped nanoparticles with a Gaussian distribution of size are calculated and discussed.     

Radiative quenching and excitation of metastable states upon differential scattering of atoms: I. Uniform quasi-classical theory

A theory of radiative-collisional transitions between the ground and metastable ¹S states of a colliding atom is proposed. The theory uses the uniform quasi-classical approximation generalized to the case of spherically asymmetric interactions. The theory takes into account the angular momentum of an emitted (absorbed) photon and allows one to calculate the total and differential scattering cross sections in a wide range of radiation frequencies including both wings and the center of the line of a forbidden atomic transition. The range of admissible collision energies and intensities of an external radiation field is restricted by the use of the adiabatic approximation, as well as the approximation of a weak coupling between the ground and excited states of a quasi-molecule, the potentials of which are assumed to be monotonically repulsive.     

A study of the transannular interaction of some amino acids and of glycylglycine with 3,3,7,7-tetramethyl-1,2:5,6-dibenzocyclooctane-4,8-dione

Summary It has been shown that the transannular interaction in a weakly alkaline medium of 3,3,7,7-tetramethyl-1,2:5,6-dibenzocyclooctane-4,8-dione with glycine, -D,L-alanine, -alanine, -butyric acid, and glycylglycine forms the corresponding aza adducts of the type of derivatives 4,4,8,8-tetramethyl-2,3:6,7-dibenzo-9-azabicyclo[3,3,1]nonane-1,5-diol derivatives with good yields.Institute of Experimental and Clinical Surgery, Tbilisi. M. M. Shemyakin Institute of Bioorganic Chemistry, Academy of Sciences of the USSR, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 43–48, January–February, 1979.     

Influence of the Density of Buffer Gas Atoms on the Shape of the HgXe(A30+) → HgXe(X10+) Excimer Band

Optics and Spectroscopy - The reasons for the discrepancies between the experimental data on the shape of long-wavelength continua near the 63P1 → 61S0 resonance line of a mercury atom in a...     

Collision of Rydberg atom A** with ground-state atom B: Optical potential

The method of optical potential was used to calculate the slow collision of Rydberg atom A** with ground-state atom B. As an example, calculations were carried out for the Na**(nl)+He system.