Table of contents

The coupled equations for electron collisions with Be⁺, including the 1s²2s and 1s²2p levels, have been solved to obtain wavefunctions for the Be ¹S ground state, and for the (e^-+Be⁺) ¹P continuum, and the solutions used to calculate the photoionization cross section. Similar calculations have been made for Mg.

The Coulomb interaction between the two electrons and residual ion in the final state of an ionizing collision between electrons and atoms is shown to influence the experimental findings of Ehrhardt et al (1972) for the triple differential cross section.

The author has compared multiphoton transition probability calculated by the momentum translation approximation with that of the perturbation theory calculation. By this comparison, it is shown that the momentum translation approximation gives a cross section which is always lower than the cross section calculated by the use of perturbation theory.

The leading term in the asymptotic expansion of the hyperfine shift in HeH has been computed with the result Delta a(R)/a( infinity )=11.361+1.901)R^-6.

The optical model for electron scattering on atoms describes both differential and total reaction cross sections. The well-known values of ionization cross sections provide a lower limit to reaction cross sections and, in the case of 100 eV electrons on argon, and upper limit to possible experimental values of differential cross sections. The present work investigates the sensitivity of the cross sections to physically-reasonable assumptions about the model and shows that it can give valuable help in deciding the consistency of different measurements of entrance channel data.

For pt. I see abstr. A41484 of 1972. Hypervirial theorems for the operator W=exp(itx) for one-dimensional systems described by potentials involving only positive powers of x have been shown to lead to a recurrence relation in the transition moment integrals T_n=(A,xⁿB) where A and B are eigenstates of the system in question. This recurrence relation is also directly derived from other hypervirial theorems. Transition moments calculated in this way compare favourably with those obtained by direct computation.

Expressions incorporating the correct phase factors are derived for the Born II scattering amplitude for ionization. The limiting behaviour of this with small momentum transfer is considered, and an expression for the high energy behaviour of the cross section, analogous to the Bethe approximation is obtained.

A truncation technique for the real time two-particle Green function is presented. The formalism is applied to the study of spectral line-broadening in plasmas and the electron correlations are explicitly included. The relationship of the present theory to other Green function methods is discussed. Lastly, the present method is compared to two other truncation procedures which have been used to analyse spectral line broadening in plasmas.

A theoretical treatment of the relaxation and transfer of atomic multipole moments due to interatomic collisions is presented, applicable to systems of emitters and perturbers with any angular momenta. Expressions are obtained for the rate constants, within the impact approximation, in terms of the elements of the scattering matrix evaluated as a function of impact parameter for an emitter-perturber collision. Processes in which the total electronic excitation energy is not conserved are excluded and collisions are assumed to occur isotropically. Explicit evaluation of rate constants has been carried out using the first-order dipole-dipole (resonance) interaction, assuming the classical straight line path approximation. Four special cases have been treated by numerical integration of the Schrodinger equation in the interaction representation. These are: J_g (ground state angular momentum)=0, J_e (excited state)=1; j_g=¹/₂, J_e=¹/₂; J_g=¹/₂, J_e=³/₂; J_g=1, J_e=1. The (¹/₂, ¹/₂) rate constants are shown to be simply related to those for the (0, 1) case. Within the context of the various approximations, numerical accuracy is expected to be better than 1%.

The ionization potential of ⁸⁶KrI is 112925+or-10 cm^-1. From possible series perturbations thus two 5s, the four 5p and four 4f levels belonging to the parentage 4s 4p⁶ are calculated.

For pt. III see abstr. A83212 of 1972. The method of paper I (see abstr. A24375 of 1972) is applied to the scattering by helium atoms of electrons between 50 and 1000 eV, and results are presented for elastic scattering and the 2¹S and 2¹P excitation. It is found that the inclusion of second order potential terms leads to cross sections which are in significantly better agreement with the experimental data than those of previous calculations.

For pt. II see abstr. A56132 of 1972. A simplified second Born approximation together with a third order approximation has been used to calculate differential and total cross sections for the electron excitation of the 3²D and 4²D states of hydrogen, the 3¹D and 4¹D of helium, and of model doubly excited states of helium. Where possible, comparisons with experimental data are made. Large corrections occur to the first Born cross sections for the excitation of the model doubly excited states and it is suggested that these corrections may also be expected to the first Born results for simultaneous excitation and ionization.

The expressions proposed by Khare (1969) for the energy loss cross sections and the first Born cross sections for the excitations of helium atom due to electron impact are utilized to calculate the mean energy loss per ion pair and the stopping power of helium gas for 50 eV-10 KeV electrons. The results are in good agreement with other theoretical values and experimental data.

The cross sections of single and double electron capture for an alpha particle passing through a helium atom have been calculated for incident ion energies ranging from 50 to 1500 keV, using the impact parameter method. The momentum transfer and exchange of electrons have been taken into account. The 2s and 2p excitations of ionized helium in both direct and captured states have been calculated by a perturbation method. The results obtained are compared with the available experimental results and other theoretical findings. The present calculated results for double capture cross sections are found to be in fairly good agreement with the experimental findings up to energy of about 750 keV. The inclusion of 2s and 2p excited states modifies the single capture cross section in better agreement with the experimental findings in the incident energy region E>150 keV. The perturbation method applied seems not suitable below 150 keV. The calculated cross sections for excitations of the resultant target helium ion and for single capture into the corresponding excited states are found to be nearly equal in the energy region E<1000 keV.

The energy dependence of spin polarization in electron resonance scattering from Ne has been measured for scattering angles of 60 degrees , 90 degrees , and 120 degrees . The results are compared with recent theoretical data and found to be in good agreement.

The excitation of helium by 20-100 keV hydrogen atoms has been investigated by the spectroscopic analysis of radiation emitted in the spectral range 3900-6000 AA during the spontaneous decay of the excited products of single collisions. Absolute cross sections for the excitation of the 4¹S, 4¹D, 4³S and 4³D levels have been determined. In the case of the 4¹S and 4¹D levels, cross sections for excitation by protons and hydrogen atoms have been compared with a relative accuracy of +or-12%. The measured cross sections are in generally poor accord with recent theoretical estimates.

For pt. I see abstr. A56119 of 1972. Ionization processes occurring in collisions of He⁺ and He with He, Ne and Ne⁺ with Ne, Ar and Ar⁺ with Ar, and Kr and Kr⁺ with Kr in a kinetic laboratory energy range from threshold up to 10 keV are investigated by electron spectroscopy. Electron spectra obtained at different collision energies, and, in some cases, at different detection angles are reported for all collision systems. Further an excitation function for the Ar (...3s3p⁶4s) autoionizing state is shown and analysed in terms of the Landau-Zener two-state model. The electron spectra of the systems He-He and Ar-Ar give clear evidence of the occurrence of autoionization of the molecular system formed during the collision. They also give evidence of the formation of the negative ions He^*-(1s2s²), Ne^*-(2p⁵3s²)²P_3/2,1/2, and Ar^*-(3p⁵4s²)²P_3/2,1/2 in He-He, Ne-Ne and Ar-Ar collisions, respectively. In the case of the collisions of He⁺ and He with He an analysis of the results on the basis of the one electron MO correlation diagram is carried out.

It is shown that trial wavefunctions for the 2p sigma _u and 2p pi _u states of H₂⁺ with three variational parameters, separable in elliptic coordinates give excellent results for the energy eigenvalues as functions of the internuclear coordinate. It is also seen that there are two minima for the energy as a function of the parameters. Earlier results for the same trial function used for the 2p sigma _u state in error because the optimization has not always been carried out for the absolute minimum.

The correlation diagram and potential energy of the N₂ system has been calculated over the whole range of inter-nuclear separation from zero to infinity. Simple methods have been employed which are designed to yield results of sufficient accuracy to be used in scattering calculations, using a minimum of computing time. Good agreement is obtained with more accurate calculations recently reported by Mulliken.

Red degraded and double headed bands of AlO at 2381.64 AA and 2388.99 AA have been excited in a low pressure dc arc and photographed at high resolution. From a study of their fine structure they have been assigned to an electronic transition F² Sigma ⁺-A² Pi _i. The final state has been identified with the state A² Pi _i recently reported at 5282 cm^-1 (T₀₀). The initial state F² Sigma ⁺ is a new electronic state located at 47190 cm^-1 (T₀₀). The rotational constants determined for these electronic states are given.

Using second quantization and operator techniques the square of the Franck-Condon overlap integral for different frequencies is derived algebraically. In contrast to similar work no integrations, series expansions of oscillator states or theorems from the theory of special functions are applied.

The authors have calculated to a high degree of accuracy correlated wavefunctions and their corresponding energies containing all the non-dynamical correlations of the non-closed shell many-electron theory by Sinanoglu and co-workers (1970). Ground as well as highly excited states of atoms and ions with three to nine electrons from beryllium to silicon are considered. Special care is applied to obtain wavefunctions of highly excited hole-states having lower states of the same symmetry, like Be I 1s² 2p²¹S, B I 1s² 2s 2p²²S, O I 1s² 2s 2p⁵³P⁰, F II 1s² 2s 2p⁵¹P⁰ and others. The methods, presented in reasonable detail, yield correlated wavefunctions accurate to approximately 0.001 au readily applicable to transition probabilities, hyperfine structure, spin-orbit coupling and other properties. Accurate wavelengths, term-splitting ratios and multiplet oscillator strengths for lines in highly ionized silicon, are given as an example of the applicability of the wavefunctions and energies obtained.

For pt. III see abstr. A11153 of 1973. The basic integrals appearing in the N-photon T-matrix for ionization of neutral atoms and electron detachment of negative ions are obtained in compact forms both for circular polarization as well as for linear polarization of incident radiation. The present results circumvent the often lengthy procedure of summing the partial amplitudes and provide a basis for investigating physically interesting limits of multiphoton transitions, analytically.

A useful new method of calculation for bound-free transitions under the momentum translation approximation for multiphonon processes is outlined.

Absolute measurements of K and L characteristic X-rays produced in thick targets of Ni, Cu, Mo, Ag, and W are reported. The data for K X-rays are compared with a theoretical result obtained by integration of the expression for the cross section given by Merzbacher and Lewis (1958). The expression for yield as a function of energy can be put into a very simple form without the need for an empirical function, and this is verified experimentally. A new absolute comparison can be made between thick-target theory and the present data for nickel and gives good agreement. Tungsten L-radiation is investigated, and spectra are obtained using a Si(Li) detector. The number of L-ionizations per proton in tungsten is found to be greater than the number of K-ionizations expected in an element with a K-shell binding energy equal to the L_III binding energy of tungsten, by a factor of 2.9. The proton bremsstrahlung is measured and the ratio of characteristic to continuous radiation found to be 1.63*10³ for 420 kV protons on nickel. This is shown to be about 3 orders of magnitude greater than for electron bombardment under optimum conditions.

High resolution intrinsic Ge(HP) and Si(Li) X-ray detectors have been used in coincidence to determine L₂ and L₃ subshell fluorescence and Coster-Kronig yields at Z=86, 88, and 94. The results are: nu ₂=0.498+or-0.028, omega ₂=0.459+or-0.025, f₂₃=0.105+or-0.011, omega ₃=0.384+or-0.020 at Z=86; nu ₂=0.516+or-0.036, omega ₂=0.493+or-0.030, f₂₃=0.053+or-0.026, omega ₃=0.408+or-0.027 at Z=88; and nu ₂=0.627+or-0.036, omega ₂=0.513+or-0.022, f₂₃=0.226+or-0.016, omega ₃=0.509+or-0.029 at Z=94. Together with previously published data, these results provide evidence that in the L₂-L₃ Coster-Kronig process, ejection of an M₅-subshell electron is energetically possible at Z=92 and that M₄- and M₅-subshell electron ejection are both possible at Z=94. These conclusions are shown to be consistent with the L X-ray line width measurements of Merrill and DuMond (1961) and with the formula put forward by Coster and Kronig (1935) for the ejected electron energy. Recent theoretical predictions of the L-subshell yields compare favourably with experiment, except when Coster-Kronig transitions close to an energy threshold are involved.