Sukanya Sur

Electronic excitation of H2 by positron impact using the CCA

The close coupling approximation has been employed in positron-hydrogen molecule collision in the fixed nuclei formulation to obtain the electronic excitation cross section of the B 1 Sigma u+ state up to the incident energy 75 eV. The elastic cross sections are found to be influenced significantly when compared with the static results. The effect of the excited state on the elastic channel enhances the elastic cross section. In the absence of any other theoretical results or measured values, excitation cross sections are compared with the corresponding electron results.

Rovibrational excitation of the hydrogen molecule by low-energy positron impact

The positron-hydrogen-molecule scattering processes have been investigated using the lab-frame rovibrational close-coupling approximation, retaining two vibrational ( nu =0, 1) and three rotational (j=0, 2, 4) states in the coupling scheme. The effect of higher vibrational states is found to be marginal. The results for the total integrated, pure vibrational and rotational excitation cross section have been reported in the energy range 0.6 to 6.0 eV. The effect of including the vibrational states enhances the total cross sections. The present results for the total integrated cross sections favour the recent measured values of Charlton et al. (1983).

Model exchange potential and e--H2 scattering

The scattering of slow electrons by hydrogen molecules has been studied in the laboratory-frame close-coupling approximation. The exchange kernel is replaced by a local model exchange potential as used by Sur and Ghosh (1983). The effect of polarisation is included through the Henry-Lane potential. The results for elastic, rotational excitation and total cross sections are reported. Fair agreement of the present results with recent measurements and other theoretical results has been obtained.

Energy levels of λx2k anharmonic oscillators using the quantum normal form

The ground state and first few excited energy levels of the generalized anharmonic oscillator defined by the HamiltonianH=−d2/dx2+x2+λx2k (k=3, 4,...) have been calculated by employing the method of quantum normal form, which is the quantum mechanical analogue of the classical Birkhoff-Gustavson normal form. The present energy eigenvalues are consistent with other tabulations of the energy levels.

Calculation of arbitrary 1s-nd excitations of atomic hydrogen by electron impact using the Glauber approximation

The 1s to nd excitations in e--H collisions are studied within the framework of the Glauber theory using a recently proposed method of reduction of the Glauber scattering amplitude. Calculations are performed in the incident electron energy range 15-400 eV for the state n=4, and for the asymptotic limit n to infinity and tabular results of properly scaled differential and integrated Glauber cross sections are presented. The Glauber results are compared with the existing theoretical predictions. A unified graphical representation of the integrated 1s to nd (n>or=4) Glauber cross sections above 50 eV normalised to the scaled asymptotic value at 100 eV presented.