Manabesh Bhattacharya

Calculation of the Integral ∫T0T′mexp(–E/RT′)T′

A technique has been developed for the calculation of the ∫T0T′mexp(–E/RT′)T′.The accuracy of the method is tested by comparing its predictions with numerical results and those of a method due to Quanyin and Su.

Evaluation of the activation energy from derivative temperature-programmed desorption curves

A set of expressions for the evaluation of the activation energy from first and second derivative temperature-programmed desorption (DTPD) have been presented for different values of the order of kinetics. Taking into consideration a large number of computer generated DTPD curves of different order of kinetics it is shown that the value of the activation energy obtained by using the present set of expressions are in good agreement with its actual value.

Protonium formation in the excited state in laser assisted antiproton-hydrogen atom collisions

Abstract A detailed analysis using the Born approximation is given of protonium formation in the first excited state ( n = 2) in laser assisted antiproton hydrogen atom collisions adopting the semi-classical model. The projectile-laser-field interaction and the dressing effects on the hydrogen atom and the protonium atom have been considered to first order in the A · p gauge. The differential cross sections for protonium ( n = 2) formation have been presented for no-photon and one-photon exchange ( l = 0, ± 1) at 50, 100 and 200 keV energies with laser frequency ω = 0.043 a.u. and laser field strength E 0 = 0.002 a.u. along with the field free results. Two interesting characteristics are noted. The differential cross sections increase slowly with the scattering angle unlike the case of electron capture by heavy particles. Secondly, contributions from the entire angular region (0°–180°) are important for the calculation of cross sections, which is a familiar characteristic in light particle scattering.

Positronium formation in the excited state in the presence of a laser field

A straightforward approach for the evaluation of the rearrangement scattering amplitude in the first Born approximation has been given for the study of positronium (Ps) formation in the first excited state (n = 2) in e+ – H(1S) collisions in the presence of a homogeneous, single mode, linearly polarized laser field embodying the full interaction potential. The projectile-laser-field interaction and the dressing effects on the target hydrogen atom and the Ps atom in the final channel have been considered to first order. The A p gauge has been adopted in constructing the dressed wave functions. The FBA scattering amplitudes have been obtained in closed analytic forms for field direction parallel to the incident positron momentum. The differential cross sections for Ps (n = 2) formation have been presented for no photon and one photon exchange (l = 0, ±1) at 50, 100 and 200 eV energies with laser field amplitude 0 = 1.0 × 108 V cm−1 and the angular frequency ω = 1.17 eV. The relations between the differential cross sections and the laser field strength, angular frequency and incident energy have also been demonstrated.

Positronium formation in a laser field

A method has been developed for the study of positronium (Ps) formation in the e++H collision process in the presence of a single-mode laser field, taking account of the full interaction. To calculate the dressing effect, the field is treated classically in the dipole approximation. As a first attempt, the differential cross sections for Ps formation without the dressing effects of the atoms have been computed for zero-photon (l=0) and one-photon (l=+or-1) exchange. Preliminary results are presented for the energies 50, 75, 100 and 200 eV with a laser field amplitude of E0=0.02, an angular frequency of omega =0.074 au and with the direction of the field parallel to the incident momentum (E0 mod mod ki). Without the dressing effect, it is noted that the differential cross sections are greatly reduced compared with the field-free results.