K. Roy

Ionization of atomic hydrogen by positron impact

A final-state wavefunction, involving three appropriate confluent hypergeometric functions, which satisfies the correct asymptotic condition is used to study positron-impact ionization of atomic hydrogen. Results are reported for the double as well as triple differential cross sections and compared with the available theoretical findings. The double differential cross section curves for different ejection angles show the presence of a cusp-like structure at the region of equal energy sharing by the outgoing positron and the ejected electron. This is in conformity with the findings of Mandal et al. (1986) at zero ejection angle but unlike the structure exhibited by the curves of Schultz and Reinhold (1990).

Ionisation of Atomic Hydrogen Under Heavy Particle Impact

Ionisation of hydrogen atoms in ground and metastable 2s states by impact of protons and antiprotons has been studied at collision energies varying from 10 to 1566keV/amu. Total and double differential cross sections are calculated employing a final continuum state wave function which incorporates distortion due to the Coulomb fields of both the projectile and the target nuclei. The present calculated results are compared with the existing experimental findings as well as other theoretical predictions.

Triple differential cross sections for electron ionisation of He

Triple differential cross sections are calculated for electron impact ionisation of He+, where the amplitude involves three confluent hypergeometric functionsThe method adopted is equivalent to the Coulomb-Born approximation. The expression for the amplitude has been reduced to a two-dimensional integral in real space and the integrals are evaluated numerically with a high degree of accuracy.

Dipole allowed and intercombination transitions in K

We have calculated 87 fine-structure energy levels of K 7+ and Ti 10+ belonging to the lowest 14 configurations within the n = 3 and n = 4 complexes using Program CIV3 of Hibbert. Relativistic effects are included through the Breit-Pauli approximation. New improved results of oscillator strengths, transition probabilities and line strengths for all allowed and intercombination transitions among these fine-structure levels are calculated using large-scale configuration interaction wavefunctions. Lifetimes of some relatively longer-lived levels are also computed. Our results are compared with a wide variety of other calculations and available experimental data. It is noted that most of our results compare more favourably with the measurements than the other available theoretical results.

^{\mathsf7+}

Abstract We calculate double differential cross sections of ionization of hydrogen by electron and positron impact considering a symmetric form of the wave function for the final state to describe the three-body Coulomb continuum state. The incident energies considered here are 100 and 250 eV and the ejected energies are 15 and 5 and 10 eV, respectively. The results are presented for various ejection angles from 0° to 180°. The present values by electron impact are compared with those of recent experimental data of Shyn and the theoretical results of Curran and Walters and it is found that they are in close agreement except at lower angles.

and Ti

Abstract Total cross sections of ionization of hydrogen atom by positron impact have been calculated for a wide range of incident energies varying from 25 to 600 eV. A symmetric form of the wave function for the final state to describe the three-body Coulomb continuum of Brauner et al. [J. Phys. B 22 (1989) 2265] is considered. The validity of using the above wave functions is demonstrated here and it is shown that our calculated values coincide with the recent experimental data of Jones et al. [J. Phys. B 26 (1993) L483] from 75 eV onwards.

^{\mathsf{10+}}

The Triple Differential Cross-Sections for ionisation of hydrogen atom bye± impact are calculated including exchange effect. A correlated three-body continuum wave function is used here for the final state. Attention is paid to equal energy sharing at the final channel where scattered and ejected energies are each 200 ev., and it is found that the exchange effect is remarkably high in this case. Present electron impact results are compared with the recent work of McCarthy et al. [1].

ions

An expression for the ionisation amplitude is obtained starting from Schrodingers equation. Triple differential cross sections are calculated using the Born approximation with two different sets of effective charges for the outgoing electrons, and the results are compared with experimental data.

Double differential ionization cross sections of atomic hydrogen by e± impact

Abstract The double electron capture process for protons passing through helium is studied using the impact parameter method in the atomic state expansion. The effect of the translatory motion of the electrons and the Pauli principle have been incorporated.

Total ionization cross section of atomic hydrogen by positron impact

Abstract The excitation cross sections for H + -He and He ++ -He collisions are calculated by distortion approximation. The present results are compared with other existing results. The cross sections for He ++ -He collisions reveal an oscillatory nature.