Resonant structure in doubly charged ion formation during multiphoton ionization of Sr and Ba atoms by infrared laser radiation

Experimental investigations of resonant structure in doubly charged ion (A(2+)) formation were carried out during Sr and Ba atom ionization by infrared laser radiation (omega = 8400-9100 cm(-1)) It has been shown that in this case the mechanism of ion formation is a two-electron process-the ions are produced immediately from the neutral atoms. It has been found for the first time that the resonant structure in A(2+) ion formation in such conditions is due to the excitation and ionization of neutral-atom mixed states. The atomic-state mixing in this case results from the Stark effect provided that the polarizability of these states is very high.