Optogalvanic detection of krypton Rydberg levels with a two-step pulsed laser excitation

The authors have used an optogalvanic detection scheme, in conjunction with a two-step pulsed laser excitation, to investigate high-lying (Rydberg) krypton levels. The excitation scheme starts from the metastable 1s 5 level, populated in the He-Kr discharge tube and uses either the 2p 2 or the 2p 3 level as an intermediate level. The transient variation of the voltage across the discharge (duration about 50 mu s) is detected as a function of the second-step laser frequency. The energy of the levels of the odd series nd(3/2) 2 and nd(7/2) 3 have been measured for n=15 to 25 with an accuracy of 0.03 cm -1 . Members of the even series nf(7/2) J , nf(9/2) J and np(5/2) 3 have also been identified and the corresponding energies measured. In the latter case, the excitation scheme involves a collisional excitation transfer from the laser populated intermediate levels to the closely lying 3d 4 ' level.