A redetermination of the lifetime of the 4s 5s ( 3S 1) level in Ca by high-rate electron—photon stepwise pulse excitation

Abstract

The radiative lifetime of the 4 s 5 s ( 3 S 1) level in Ca was measured using two-step excitation of atoms in a beam which traverses a cold-cathode Penning discharge, where, by electron impact the atoms are excited to the metastable 4 s 5 p ( 3 P 2, 1, 0) states. Immediately thereafter, the beam is crossed with a pulse-modulated cw dye laser beam to populate the final state selectively. Using a pulse-modulation frequency of 0.5 MHz, a preliminary value of 12.4 ± 0.5 ns was obtained with a statistical error of 0.4%. The wide limits of systematic error reflect an assumed uncertainty in the excitation function and possible distortion in the fluorescence decay requiring further study.