Non-Maxwellian rate coefficients for electron and ion collisions in Rydberg plasmas: implications for excitation and ionization

TL;DR

This paper investigates how non-Maxwellian electron energy distributions, specifically bimodal and kappa-distributions, influence collisional rate coefficients in Rydberg plasmas, with implications for plasma diagnostics.

Contribution

It introduces calculations of rate coefficients using non-Maxwellian distributions, highlighting their impact on plasma processes and diagnostics in tokamak divertor regions.

Findings

High-energy tails significantly alter rate coefficients.

Non-Maxwellian distributions affect excitation and ionization rates.

Implications for plasma diagnostics in laboratory settings.

Abstract

Scattering phenomena between charged particles and highly excited Rydberg atoms are of critical importance in many processes in plasma physics and astrophysics. While a Maxwell-Boltzmann (MB) energy distribution for the charged particles is often assumed for calculations of collisional rate coefficients, in this contribution we relax this assumption and use two different energy distributions, a bimodal MB distribution and a $\kappa$-distribution. Both variants share a high-energy tails occurring with higher probability than the corresponding MB distribution. The high energy tail may significantly affect rate coefficients for various processes. We focus the analysis to specific situations by showing the dependence of the rate coefficients on the principal quantum number of hydrogen atoms in n-changing collisions with electrons in the excitation and ionization channels and in a temperature range relevant to the divertor region of a tokamak device. We finally discuss the implications for diagnostics of laboratory plasmas.