Relaxation of low energy positrons in molecular gases

The calculations of thermalization times and spatial relaxation profiles of the positron transport properties in H_2, N_2 and in mixture of N_2 and CF_4 are presented. Recently, the data needed to compile comprehensive set of cross sections for these gases became available which made our calculations possible. The main difference between positron and electron transport is the existence of the effect of positronium (Ps) formation which changes the number of particles and has a strong energy dependence. The relative magnitude of positronium formation to electronic excitations and the relative positions of their thresholds control the efficiency of thermalization and non-conservative transport phenomena. The effect of vibrational and rotational excitations on thermalization has been considered and relative contributions were determined. Our calculated thermalization data are in reasonably good agreement with the experimental data of Al-Qaradawi et al. (2000).

Publications de l'Observatoire Astronomique de Belgrade

Publications of the Astronomical Observatory of Belgrade

84

0373-3742

N/A

N/A

4