CW laser spectroscopy of autoionising 6p 3/2 nl states of Barium

Abstract

6pnl states of Ba with l55, excited with two narrowband, tunable CW lasers have been studied. In the first excitation step 6snl states were populated from metastable states of the 5d configuration: to 6s40h (l"5) states in the absence, and to parabolic 6pnk (n"30, 35, 40) states in the presence of an electric field. The atomic motion was used to adiabatically reduce this field to zero before applying the second excitation step to high-l 6p nl states (Stark-switching). A slow decrease in the autoionisation rate for increasing value of l and, in case of 6pnh, a dependence on the fine-structure state was measured. The narrowest autoionisation linewidth observed is 113(11) MHz, relatively close to the 20 MHz linewidth corresponding to the radiative lifetime of the 6p state of the Ba>-ion.