Pressure-induced frequency lineshifts in the nu(2) band of ammonia: An experimental test of the Rydberg-Ritz principle

Self-induced frequency lineshifts of NH3 in the v(2) band have been measure d for low J and K values. By combination with Lineshift parameters previous ly published for other frequency ranges, it is possible to consider several level manifolds connected by superabundant numbers of transitions. Using s tatistical tests, these results lead to a quite meaningful experimental con firmation of the nonadditivity of pressure lineshifts, that is, the Rydberg -Ritz combination principle cannot be extended to collisionally perturbed s ystems. (C) 1999 Academic Press.