[en] A model for ion-atom collisions at intermediate energies is proposed in which the conventional close-coupled approach and the eikonal theory of Glauber are unified. The results are presented for direct H(1s) → H(2s) excitation by proton impact in a two-channel formalism. The conditions under which the model becomes applicable to electron-atom scattering are also examined. (author)

[en] Conditions of the experiments are considered for observation of parity nonconservation in radiative atomic transitions in the case of hydrogen - like atoms and two-electron ions. Calculations are carried out for H, He C⁺³ and Cu ⁺²⁷ limitations on a beam and residual gass density, external magnetic and electric fields are calculated. The time of the experiment is also estimated. The conditions appear to be really practible only in the case of Cu⁺²⁷

[en] Shanks' (J. Math. Phys.; 34:1 (1955)) generalisation of Aitken's delta² transformation is presented as a ratio of persymmetric determinants, and an algorithm for calculating these is given. The superiority of the generalised transformation over repeated delta² transformations for summing perturbation series is shown. (author)

[en] Simple expressions are given relating linear and circular polarization of radiation, emitted following collisions of electrons with atoms, to Fano-Macek orientation and alignment parameters (Rev. Mod. Phys. 45: 553 (1973)). The p→s and d→p cases are considered explicitly, with and without unresolved fine structure. Several errors in the literature are corrected. Results are given for Lyα at 100 eV. (14 references) (author)

[en] The lifetimes of some levels of the 4d⁵5p and 4d⁴5s5p configurations have been determined by zero-field level-crossing technique. The results are: 4d⁵5p: tau(⁷P₄) = 14.4(8) ns; tau(⁷P₃) = 15.8(8) ns; tau(⁷P₂) = 13.6(7) ns. 4d⁴5s5p: tau(⁷P₄) = 5.7(6) ns; tau(⁷P₃) = 10.2(5) ns; tau(⁷P₂) = 6.0(5) ns; tau(⁷D₃) = 12.1(10) ns; tau(⁷D₂) = 8.2(8) ns. (Auth.)

[en] Ionisation of atomic systems by fast ions is considered. A second-order quantum theory is derived which correctly accounts for all distortions of the initial- and final-state wavefunctions arising from Coulomb interactions between three charged particles. The present transition amplitude is the rigorous first order (or lowest order) approximation to the exact scattering amplitude for ionisation treated by the Faddeev equations in the distorted wave formalism. The problem is briefly studied by the impact parameter method as well, and its equivalence with the full quantal treatment is proved (for projectiles mainly scattered forward) in the limit of very large valUes of the reduced mass. As an illustration of the present theory, ionisation of atomic hydrogen by proton impact is examined at incident energies between 25 and 200 keV. Comprehensive comparisons of available experimental data with singly differential as well as total cross sections for electron ejection are made and the validity of the present method is assessed. (author)

[en] The energies and widths of the lowest ¹P⁰ and the second ¹S resonance below the n=2 threshold in H^- have been determined by a scattering calculation employing the algebraic variational method. (Auth.)

No abstract available

[en] As part of a kinetic study of XeF laser media, we have followed the time evolution of the Ne*, F*, and F*₂ densities in e-beam excited Ne/Xe/NF₃(F₂) mixtures. The Ne* and F* densities were monitored by laser absorption while the F₂* was observed in emission at 158 nm. Rate coefficients for the quenching of these excited states by Ne, Xe, NF₃, and F₂ have been determined. The radiative lifetime of the F₂* was measured to be 41 +- 4 x 10^-9 sec

[en] The recent discovery by Khare that choosing the CS partial wave parameter l-bar to be the initial orbital angular momentum, l/sub i/, leads to a simple differential scattering amplitude for definite polarization transitions is examined in detail. It is found that the resulting scattering amplitude formula, which is a rotation of the usual McGuire--Kouri formula, predicts nonzero magnetic transitions in all frames except that whose Z axis always points in the final observation direction R. A detailed comparison of l/sub i/ and l/sub f/ labeling is made and it is shown that both lead to nondiagonal approximations to the p-helicity amplitude, T/sup J/(jlambdavertical-barj₀m₀), and to differential scattering amplitudes which have the proper limiting behavior at small and large scattering angles. In addition it is shown that both l/sub i/ and l/sub f/ labeling yield identical results for all degeneracy averaged cross sections, including the general relaxation cross sections. Further, we show rigorously that if the quantization axis is along a direction perpendicular to the plane of the incident and final momenta, then the l/sub i/ and l/sub f/ labeled cross sections are identical. It is argued on the basis of available numerical results and on physical grounds that the l/sub i/-labeled CS is preferred over the l/sub f/ CS for calculating magnetic transitions quantized along the incident momentum. We further expect the l/sub f/ CS to be preferred for calculating magnetic transitions quantized along the final momentum. However, other l-bar choices may be better yet for magnetic transitions in general