COLLISION-INDUCED RESONANCES IN MULTIPHOTON IONIZATION OF ATOMS

The spectrum of double quasi-resonant three-photon ionization of atoms in a gas cel is investigated in the impact collision approximation. It is shown that dephasing atomic collisions induce extra resonances in the multiphoton ionization spectrum. These resonances occur when the frequency of one of the exciting radiations is equal to the frequency of transition between two unpopulated levels. The amplitude of the resonances depends on the buffer gas pressure, and their width is determined by the Doppler broadening of the atomic transitions. The analogy between the collision-induced resonances and the resonances arising due to the stochastic nature of the exciting radiation and ac Stark splitting is pointed out. © 1990.