Electron energy deposition in molecular hydrogen : a monte-carlo simulation using convergent close coupling cross sections.*

A Monte-Carlo simulation of electron energy deposition in molecular hydrogen was conducted with the aim of calculating standard energy deposition parameters. These include the mean energy deposited per ion pair (w) and the mean number of induced dissociations. Molecular convergent close-coupling (MCCC) cross sections were used as input into the simulation. These provide a substantial improvement in accuracy over other commonly used electron-H₂ scattering data sets. The calculated high energy value of w was 36.3 eV, yielding excellent agreement with the high energy value of 36.5 ± 0.3 eV recommended by the ICRU. An analysis of the spread in calculated values due to the uncertainty in the input cross sections was also conducted. Qualitative features of the number of induced dissociations observed experimentally were reproduced by the simulation.  Specifically, the incident electron energy at which secondary electrons produced via ionisation begin to induce more dissociations than the primary electron was identified. Finally, a comparison of the results with those of a previous simulation highlights the effect of accurate collision data on the results of such simulations.