  In our previous research, it has been demonstrated that such inelastic
processes in atom Rydberg-atom collisions, as chemi-ionization and (n-n')
mixing, should be considered together. Here we will review the present state of
the art and the actual problems will be discussed. In this context, we will
consider the influence of the (n-n')-mixing during a symmetric atom
Rydberg-atom collision processes on the intensity of chemi-ionization process.
It will be taken into account H(1s) + H*(n) collisional systems, where the
principal quantum number n $>>$ 1. It will be demonstrated that the inclusion
of (n-n') mixing in the calculation, influences significantly on the values of
chemi-ionization rate coefficients, particularly in the lower part of the block
of the Rydberg states. Different possible channels of the (n-n')-mixing
influence on chemi-ionization rate coefficients will be demonstrated. The
possibility of interpretation of the (n-n')-mixing influence will be considered
on the basis of two existing methods for describing of the inelastic processes
in symmetrical atom Rydberg-atom collisions.

Atomic Physics;Solar and Stellar Astrophysics