A mechanism of two-electron multiphoton ionization of atoms

I. S. Aleksakhin, Nikolai B. Delone, I.P. Zapesochnyi +1 more

I. S. Aleksakhin, Nikolai B. Delone, I.P. Zapesochnyi +1 more

Anne L’Huillier, Goran P. Wendin

І. І. Бондар, В. В. Суран

The experimental investigation of the formation of doubly charged ions by the multiphoton ionization of Ba atoms by simultaneous irradiation with the fundamental radiation of a colour centres laser (ω = 8800–8880 cm −1 ) and its second harmonics was carried out. A two-electron mechanism was observed to be responsible for the formation of these ions; they are formed as a result of the excitation and subsequent ionization of strongly perturbed states of neutral Ba atoms.

Yves Gontier, M. Trahin

І. І. Бондар, В. В. Суран, Denys I. Bondar

Despite inherently complex multiphoton dynamics, our observations show that Ba double ionization with an infrared laser (8800--8920 cm${}^{\ensuremath{-}1}$) resembles a single-photon process; namely, its probability is proportional to the laser intensity. In this regime, single-electron ionization is due to a four-photon resonant transition through the highly perturbed state $6{p}^{2}\phantom{\rule{0.16em}{0ex}}{}^{1}{D}_{2}$, whereas double ionization is realized by the two-electron mechanism. Furthermore, we argue that these conclusions are valid for other alkaline-earth-metal atoms and other parameters of laser radiation.