ON THE EXTENSION OF THE RYDBERG-RITZ PRINCIPLE TO THE COLLISIONAL RELAXATION OF MOLECULAR AND ATOMIC LINES

As shown by recent experimental results, the frequently used additivit y rules for the collisional broadening and shift are not exact since t he Rydberg-Ritz combination principle cannot be extended to the relaxa tion-modified frequencies of atomic and molecular spectroscopic transi tions. We present a treatment allowing the identification of additive and nonadditive parts of the relaxation. We conclude that even in case s when additivity approximately holds, this does not mean that the rel axation of the lines can be reduced to the relaxation of their initial and final states. (C) 1997 Published by Elsevier Science B.V.