Configuration interaction effects in the 4s 2nd 2D [formula omitted] Rydberg series of neutral gallium investigated with pulsed dye lasers

Abstract

We investigated the perturbation of the 4 s 2 nd 2D 3 2 , 5 2 Rydberg series in gallium due to configuration interaction with the 2D term of the 4s4p 2 configuration. The high 2D levels were populated by stepwise excitation using 5s 2S 1 2 as the intermediate state. The atoms were excited in an atomic beam apparatus by two pulsed dye lasers. We determined the position of the series members accurately from the forbidden 5s 2S 1 2 - nd 2D 3 2 , 5 2 transitions (19 ⩽ n ⩽ 34). The transition probability of these forbidden lines was strongly increased by applying a weak electric field during the excitation. The scalar polarizability of the d levels was measured too. The Rydberg atoms were detected by means of the field ionization technique. The fine structure splitting of the high d levels has been resolved for the first time. The splitting is not proportional to n ∗−3 over the range of observation and is enlarged dramatically by the perturbation. A description of the effects is presented in the framework of perturbation theory with Hartree-Fock values as a first-order approximation. Level values for the autoionizing 4s4p 2 2D 3 2 , 5 2 levels are predicted and compared with observations.