Table of contents

For pt. I see ibid., vol. 6, 1435 (1973). Coupling terms which were previously omitted are retained in a distorted wave polarized orbital calculation of electron impact excitation of the 1s to 2s transition in H and He⁺. The results for H are in very good agreement with the best close coupling results are low energies. For He⁺ the previous results are reduced by 18% at threshold, and fall 50% below experiment there.

The spectrum of resonantly scattered light at right angles to a sodium atomic beam is reported. The light source was a CW dye laser tuned to resonance with a hyperfine component of the D₂ line, and incident at right angles to the atomic beam. The spectrum, with the Stark effect sidebands, was recorded as a function of both the laser intensity and its detuning from resonance. The overall resolution is better than 20 MHz.

It is shown that the orthogonality condition referring to total scattering states with identical boundary conditions is satisfied in the random phase approximation. This orthogonality condition is also discussed for elastic scattering.

The KLL Auger electron production cross section has been measured for collisions between Na⁺, Na²⁺, Ne⁺, Ne²⁺, and N⁺ ions and Ne and N₂ targets. Over a narrow velocity range (0.3-0.9au), the data reveal a dramatic dynamic effect in the 2p pi vacancy occupation probability factor N_pi . This is in contrast to current available theories which invoke a static factor N_pi .

The relative error in a lower bound formula given previously by the authors is shown to approach zero more rapidly than the corresponding error of the Rayleigh upper bound.

It is shown that the eikonal-Born series method agrees well with the recent experimental data of Teubner et al (1973) for elastic scattering of electrons by atomic hydrogen. The method is compared with other theoretical results (Born, Glauber, static potential) and a wavenumber and the momentum transfer dependence of the successive terms in the Born and Glauber series is analysed.

The problem of singlet-triplet mixing in helium is discussed. Some obscurities in the existing formalism are removed and a new parameter-the mixing factor-is introduced, which is more convenient in the analysis of experimental work.

A general formula for the T-matrix in the resonant scattering of electrons by molecules is given and an expression deduced for the total cross section out of a given initial state which differs from the simple 'golden rule' formula. It is pointed out that the S- matrix is not exactly unitary if a local approximation is used for the imaginary part of the complex potential energy.

The basic equation for the scattering amplitude as determined from a multistate eikonal description of electron-atom collisions is presented. The relationship with other semiclassical treatments is examined. Four-state eikonal calculations of the cross sections for elastic and the 2s and 2p excitations of H(1s) by electrons with incident energy E in the range 13.6 eV<or=200 eV are carried out, and are compared with other refined theoretical treatments and with experiment.

Multiphoton ionization rates for circular and linear polarization are calculated at threshold for various hydrogenic s states in the framework of ordinary perturbation theory. Circularly polarized light turns out to be more efficient in many cases.

It is shown that for transitions 2s to np in lithium-like ions the Born and Coulomb-Born approximations differ by less than 10% for incident energies greater than about 8 times threshold. This contradicts the results obtained by Kastner et al (1972) for excitation of Si¹¹⁺.

Bands assigned to two systems of the HoF molecule have been observed in absorption in the region 4500 to 5650 AA. Analysis shows that they have a common lower state which is probably a component of a multiplet ground state with Lambda >2.

A two-dimensional model of three-body breakup with short range forces is described. The variational principle of Bryce and Mandl (1972) is applied to this model and reduced to a set of linear equations. Nonlinear parameters are determined by minimizing the deviation from unitarity. As the number of parameters in the trial wavefunction increases, the scattering amplitudes are shown to converge. For a complete solution of the problem the variational calculation is supplemented by the Born approximation. It is concluded that more complicated variational calculations are feasible.

A variational method, analogous to that of the Kohn method in potential scattering, is derived which solves integro-differential equations with asymmetric kernels. The method is applied to S-wave elastic scattering of electrons from hydrogen atoms in the polarized-orbital approximation.

The second order potential approximation of Bransden and Coleman (1972) is applied in a partial wave formalism to the elastic scattering of electrons from hydrogen and helium atoms. Differential, integrated, and total cross sections are presented for hydrogen in the energy range 100-200 eV and for helium in the range 50-500 eV. A one-channel approximation is used and the effect of exchange is included to first order in the potential. Conclusions are drawn as to the validity of the impact parameter approximation used in previous applications of the method.

Various magnetic resonances appearing in optical pumping experiments have been analysed theoretically and experimentally. However, there is little work on the saturation effects caused by strong RF fields. Recently, The saturation effects of the multiple quantum resonances and of the Haroche resonances have been investigated by Stenholm (1972) and by Tsukada and Ogawa (1973). The saturation effects are treated for the more general case of a static magnetic field in an arbitrary direction with respect to the oscillating RF field. The experimental results are compared with the exact solutions computed by the numerical integration of the Bloch equation. It is shown experimentally and theoretically that the resonances similar to the Haroche resonance appear at omega /sub ///=n omega , where omega /sub ///= gamma H/sub ///, n is an integer, H/sub /// is the parallel component of the static magnetic field with respect to the oscillating RF field, and gamma is the gyromagnetic ratio.

The cross section sigma for dissociative attachment is calculated as a function of electron energy E, in the framework of a theory given by Bardsley (1968). The cross section sigma (E) exhibits vertical breaks at the position of the vibrational levels of the target molecule; the shape of the curve sigma (E) and the isotope effect are in reasonable agreement with experiment. An attempt is made to fit the potential curve of the compound state HCl^-, and to obtain a set of possible potential curves, all of them lying above the potential curve of HCl in the Franck-Condon region.

For pt. I see abstr. A33050 of 1973. The Eikonal distorted wave method is used to analyse the inelastic scattering of electrons and protons by helium atoms at intermediate energies. Detailed calculations are performed for the excitation of the 2¹S and 2¹P states.

For pt.III see abstr. A24407 of 1972. The triple differential cross section for the electron impact ionization of hydrogen atoms is calculated in the Coulomb-projected Born approximation, including exchange, and detailed comparison is made with the ordinary Born result. The calculations are done for a variety of energies and angles of the two secondary electrons in coplanar and non-coplanar geometries. Appreciable differences occur in the results predicted by the various approximations.

The elastic and the 2s and 2p inelastic scattering of ground-state hydrogen atoms by helium is examined in the Born, unitarized-Born and multistate impact-parameter formulation of heavy-particle collisions, with incident energies E in the range 6.25<or=E<or=225 keV. The failure of Born's approximation to provide an adequate description of both small angle elastic and inelastic scattering and large-angle inelastic scattering is graphically displayed.

The decay of the 1s₅ metastable state of xenon has been measured by means of an absorption technique in the afterglow of a pulsed DC discharge. At the same time the decay of excited Xe₂* molecules has been measured by monitoring the ultraviolet continuum radiation. It is shown that these excited molecules are formed in two-body and three-body collisions between metastable 1s₅ atoms and ground state atoms. The rate coefficient for de-excitation of 1s₅ state by two-body collisions is determined as 35*10^-16 cm³ s^-1 and and the rate coefficient for de-excitation by three-body collisions as 8.55*10^-32 cm⁶ s^-1. The diffusion coefficient of Xe(1s₅) in Xe is D_M=52*10¹⁶ cm^-1 s^-1.

Eight members of the He II resonance series have been studied photographically at electron densities around 1.4*10¹⁷ cm ^-3 in a reproducible Z-pinch plasma. The results show that small shifts to shorter wavelength occur although the magnitudes are smaller than 0.03 AA even for the 9s-1p transition (for which the largest shift is expected theoretically). The measured shifts are compared with several theories proposed previously.

As a preliminary study of level crossing experiments, the problem of absorption sidebands of a gas submitted to a radiofrequency (RF) Stark field has been reinvestigated. Particular attention is paid to the case of quadratic Stark effect when a static electric field is added to the RF one. The main features are; the absorption spectrum becomes asymmetrical, and besides the usual even sidebands, odd ones appear. Calculations are made quantizing the RF field and using the resolvant formalism.