The results of semi-classical calculations of rate coefficients of $(n-n')$-mixing processes due to collisions of Rydberg atoms $He^{ *}(n)$ with $He(1s^2)$ atoms are presented. It is assumed that these processes are caused by the resonant energy exchange within the electron component of $He^{ *}(n)+He$ collision system. The method is realized through the numerical simulation of the $(n-n')$-mixing processes, and is applied for calculations of the corresponding rate coefficients. The calculations are performed for the principal quantum numbers $n,\mbox{ } n'$ in ranges $4 \le n < n' \le 10$, and the atom and electron temperatures, $T_a, T_e$, in domains $5000K \le T_{ a} \le T_{ e} \le 20000K$. It is shown that the $(n-n')$-mixing processes can significantly influence the populations of Rydberg atoms in non-equilibrium weakly ionized helium plasmas with ionization degree $\sim 10^{ -4}$. Therefore, these processes have to be included in the appropriate models of such plasmas.
Categories: astro-ph.SR physics.chem-ph