Table of contents

A statistical weighting procedure is used to calculate the fluorescence yields omega _K and omega _L23 for various defect atomic configurations of the argon atom. The changes in fluorescence yield which accompany atoms with multiple vacancies in various shells should be included when determining inner shell ionization cross sections from X-ray data in heavy ion-atom collision studies. The general features discussed may be important for solid as well as gaseous targets.

A modified Doppler shift technique has been applied to the beam-foil light source to determine unambiguously and correctly the charge of nitrogen ions from which spectral lines are emitted.

The spectral profile of an isolated absorption line is related to the plasma dispersion function and/or the complex error function. A simple method for computing such profiles is given. The results can also be applied to calculation of the spectral profile emitted by a lamp.

The authors describe the numerical methods used in two independent general computer programmes for the solution of the relativistic forms of the Hartree-Fock equations for atomic configurations. Results are given for a few representative cases.

A new variational method is suggested for elastic scattering problems which involve long range polarization forces. Through a more appropriate choice of trial function, the method requires fewer variational parameters than the usual Hulthen-Kohn procedure and provides a variational bound on the phase shift. Sample results are obtained for electron and positron scattering from hydrogen.

Solutions of the coupled equations for e-He⁺ scattering are used as final states in the matrix element for photoionization of metastable He. Results are given for both the elastic and inelastic scattering regions of He⁺, including oscillator strengths for photoexcitation of the lowest few resonance states of He.

The use of the polarized orbital method in the case of alkali atoms is thoroughly discussed. It is shown that if the POM method is applied in a consistent manner, the results for elastic scattering are as accurate as the close-coupling calculations in the energy range up to the first threshold.

For Pt. I, see ibid., vol.4, 658 (1971). A modified close coupling method is proposed using an expansion of the total wavefunction in the polarized target orbitals in order to take fully into account the polarizabilities of all the states which are retained in the expansion, and consequently of the long range electron interaction. This multichannel polarized orbital theory is a way to improve the results for elastic and inelastic scattering at low energies and is particularly appropriate to the study of excited states near threshold.

The absorption oscillator strength of the (0,0) band of the CO Cameron system has been determined as 1.62*10^-7+or-5%.

Studies of generalized oscillator strengths as a function of incident electron kinetic energy in the range 60-150 eV have been made for cadmium using a crossed beam high resolution electron energy loss spectrometer. Absolute generalized oscillator strengths have been derived by normalizing the resonance transition, 5¹S to 5¹P, to the optical oscillator strength at zero momentum change. The reduced matrix elements (5¹S//r²//6¹S) and (5¹S//r²//7¹S) were found to be 6.6 au+or-25% and 2.3 au+or-50% respectively, and the electric quadrupole transition probabilities A(5¹S to 5¹D) and A(5¹S to 6¹D) calculated as 2588 s^-1+or-30% and 572 s^-1+or-40% respectively.

Differential and integrated cross sections for 3s-4s excitation of sodium by electrons are given in an energy range from 25-500 eV, using third order approximations. The 3s, 3p and 4s intermediate states are included in the calculation. Large deviations from the first Born approximation are found, caused mainly by the 3p state (polarization). Above 500 eV first Born and third order results are in fair agreement. Third order results compare well with some experimental data, while first Born results are much too low.

Using atomic structure and atomic collision programs developed, respectively, by Eissner and Nussbaumer (1969, 1970) and Eissner (1970), collision strengths have been computed for transitions, produced by electron impact, between terms of the following configurations of the following ions: N V, Si XII: 1s²2s, 2p, 3s, 3p, 3d; Fe XIII: 3s² 3p², 3s 3p³, 3s² 3p 3d; Fe XIV: 3s² 3p, 3s 3p², 3s² 3d; Fe XV: 3s², 3s 3p, 3p², 3s 3d; Fe XVII: 2p⁶, 2p⁵ 3s, 3p, 3d. The calculations are in a configuration interaction representation and in LS coupling. The collision problem is solved by the distorted wave approximation and the results obtained are found to be in good agreement with the results of close coupling calculations, where such a comparison can be made.

Differential cross sections for the ejection of electrons from helium by 100 and 300 keV protons are calculated using a classical three body collision theory. Comparisons are made with the experimental and quantum mechanical results. For not too large angles of ejection the classical orbit integration cross sections agree very well with the experimental values, in contrast to the quantum mechanical Born calculations.

Laboratory measurements of excitation rate coefficients for eighteen transitions in neon VII are presented. These were done by measuring the intensities of the corresponding spectral lines and at the same time determining the electron temperature by a laser scattering technique. The results are considered to be accurate to about a factor two absolutely and about +or-50% relatively. Within this accuracy they are found to be in agreement with the theoretical values due to Eissner except for X(2s2p 3P⁰-2s3d ³D) which is six times smaller than the theoretical value.

The polarizability tensors of (2p)⁵3s ³P₂ neon are calculated, using a double perturbation expansion to include the effects of electron correlations to first order. The calculated average polarizability is larger than the experimental value. Inclusion of electron correlations is found essential to account for polarizability anisotropy.

The fourth lowest electronic state in N₂, W ³ Delta _u, serves an important function in channelling the flow of energy through the molecule following excitation. The strong transition rate between the W ³ Delta _u state and the readily excited B ³ Pi _g state, as indicated by the intensity of the W-B infrared system, lends added significance to this role of the W ³ Delta _u state. A discussion of the various possible processes which may involve such a state includes the description of two effects, intrasystem cascading and confluent metastability, to which the relationship among the lower states of N₂ gives rise. The most recently determined values for T_e, omega _e, and x_e omega _e are given as 59808, 1501.4, and 11.6 cm^-1. Origins are tabulated for eighteen bands in two systems of the W ³ Delta _u state and potential energy curves are presented for that state and the three lying beneath it.

By the use of a 40 cm curved-crystal spectrograph of transmission type, the L spectra of rare earths ⁶⁴Gd to ⁷¹Lu have been investigated. The high frequency satellite L beta ₂^I has been reported in the case of ⁶⁶Dy, ⁶⁷Ho and ⁶⁹Tm for the first time at wavelengths of 1609.8 x.u., 1555.1 x.u. and 1450.6 x.u. respectively. Its wavelength in the case of ⁶⁸Er, ⁷⁰Yb and ⁷¹Lu has been redetermined. It has not been observed in the spectra of ⁶⁴Gd and ⁶⁵Tb. The origin of the satellite L_IIIM_IV to M_IVN_V on the basis of the multiple ionization theory. The measured wavelength values are found to be in good agreement with those calculated for this transition.

The self broadening of three doublets in the spectrum of potassium at low densities was investigated in emission from weak dc and rf discharges. The use of a double recording Fabry-Perot interferometer allowed an accurate measurement of the ratio of the broadening constants of the doublet resonance levels to be made. The value obtained 1.54+or-0.09, is in good agreement with recent calculations. The absolute values of the broadening constants are less accurate owing to experimental uncertainties in the vapour density but do not differ significantly from the theoretical values. The effects of nonresonance interactions on the broadening and shift are discussed.

Absolute multiplet strengths of 4²L to 4²L' transitions of sodium sequence have been obtained by nuclear charge expansion method and compared with those listed in critical compilation.

The weak predissociation in the v=1 and 2 levels of A ² Sigma ⁺, previously attributed to a ² Sigma ^- state crossing on the inner limb of the potential curve of A ² Sigma ⁺, has been reexamined assuming crossing on the outer limb. It can be accounted for either by a ⁴ Pi state or by a ⁴ Sigma ^- state, of which the latter seems more probable. This can account for the different strengths of lines from the F₁ and F₂ components of A ² Sigma ⁺.