Laser-induced inner shell vacancies in doubly ionized argon

The creation of laser-induced inner shell vacancies in doubly ionized Ar atoms is reported. First, theoretical calculations are performed for different laser systems and as much as 30% of doubly ionized Ar atoms in the [Ne]3s3p5 configuration with a 3s shell vacancy at optical and near-infrared frequencies are predicted. Analysis of the results shows that the mechanism for creation of the inner shell vacancy is a non-sequential double ionization process. Finally, the radiation spectrum of Ar in the field of an intense Ti:sapphire/Nd:glass laser system at 1053 nm has been measured, and the line corresponding to the fluorescence emission due to radiative filling of the created inner vacancy in the 3s shell is observed.