The Mixing of Metastable States of Barium Atoms Induced by the ac Stark Effect

We present the results of experimental investigations of atoms perturbed by laser radiation under conditions when the energy of a Stark-shifted level becomes close to the energy of a neighboring level. © 2000 MAIK “Nauka/Interperiodica”. PACS numbers: 32.60.+i, 32.80.–t 1 This paper presents the results of experimental studies of atoms perturbed by laser radiation under conditions when the change δEn in the energy of some level n is comparable with the difference ∆Enk between the energy of the considered level n and the neighboring level k (∆Enk), i.e., δEn ≈ ∆Enk. Note that this effect was theoretically predicted in [1, 2], but no experimental observation of this effect has been reported until recently. We experimentally studied the perturbation of 6s5dD1 and 6s5dD2 metastable states of Ba atoms. To perturb these levels, we employed radiation of a colorcenter laser (CCL) with a frequency tunable within the range ω1 = 8650 – 8900 cm–1. The field strength of laser radiation in our experiments was equal to e1 = 5 × 105 V/cm. The duration of laser pulses was τ = 4 × 10−8 s. This radiation strongly perturbs the 6s5dD2 state of Ba atoms, since the frequency range covered by our laser includes the frequency ωnm = 8845 cm–1, which corresponds to a one-photon transition from the 6s5dD2 state to the 6s6p state. Under these conditions, the dynamic polarizability αn of the 6s5dD2 state should be large, and its frequency dependence can be represented as [2]