Andrew and Dermot’s paper on positron cooling in small molecules published in PRL!

We performed Monte Carlo simulations of positrons cooling in N2 and CF4 gases, which are used ubiquitously as buffer gases in the leading positron “Surko” traps. We highlighted the possible importance of positron-positron interactions as a mechanism to rapidly Maxwellianize the positron distribution during the cooling dynamics, and the role of multiple vibrational (de)excitations in reducing the positron temperature. See below for videos showing positron cooling in CF4 with and without positron-positron interactions, and also for N2, alongside comparison with experiment.

Phys. Rev. Lett. 130, 033001 (2023)