Radiative lifetimes of the lowest ${^3{\rm P}}_1$ metastable states of Ca and Sr

Abstract

The lifetimes of the lowest 3P1 states of Ca and Sr have been measured in atomic beam experiments. These measurements have been made by observing the exponential decay of the fluorescence emitted from excited states populated either by a discharge or a dye-laser pumping. In both cases, the velocity distributions of the radiating atoms were also measured by a time-of-flight technique. Our results show that the lifetime measurements using the discharge excitation are hampered by a systematic error introduced probably by cascade transitions that repopulate the upper energy levels of the transitions of interest. The radiative lifetimes of the 4s4p 3P1 state of Ca and 5s5p 3P1 state of Sr are determined to be 0.34 ± 0.02 ms and 21.3 ± 0.5 μs, respectively.