Optical laser spectroscopy and hyperfine structure investigation of the 102S, 112S, 82D, and 92D excited levels in francium

Abstract

The authors present an extension to low-lying states of francium (10s, 11s, 8d, 9d) of a previously published high-resolution experiment performed on the ns and nd Rydberg levels. These four levels were investigated at CERN with the on-line mass separator ISOLDE using stepwise laser excitation in collinear geometry. Accurate energy measurements lead to a more reliable determination of the quantum defects of the whole ns and nd series, together with the ionization potential for 212Fr (nuclear spin I=5) which is found to be 32848.872 (9) cm-1. The measurement of the fine structure splittings for the nd 2D3/2, 5/2 doublets was completed at the same time. The main result of the study is the first observation and measurement of hyperfine structures in 2S and 2D states.