  We propose an algorithm for calculating matrix elements of the non-linear
Boltzmann equation collision integral in isotropic case. These matrix elements
are used as starting ones in the recurrence procedure for calculating the
matrix elements of the collision integral, which is non-isotropic with respect
to velocities, as described in our previous paper. In addition, isotropic
matrix elements are of independent interest for the calculation of isotropic
relaxation in a number of problems of physical-chemical kinetics.
  It is shown that the coefficients of the isotropic matrix elements expansion
in terms of $ \Omega $ -integrals are connected by recurrence relations that
allow us to calculate them sequentially.
