Radiative lifetimes of Am I atomic levels.

Abstract

The lifetimes of several atomic levels of Am I that are connected by electric dipole transitions to the ground state have been measured. The Am atoms were excited by light pulses from a cw single-mode dye laser with the aid of an optoacoustic modulator. The decay curve of the delayed emitted photons was measured by counting single photons in the beam-off periods. The lifetimes of 14 levels in the wavelength region between 6405 and 4265 A were measured using Am-metal vapor. The metallic Am was obtained by reducing AmO/sub 2/ with La at 1500 /sup 0/C in a high-vacuum system and collecting Am on a catcher foil. The Am vapor was then produced by controlled reevaporation from the foil at a temperature of about 800 /sup 0/C. These lifetime measurements, in combination with the line intensities from a hollow-cathode discharge, allow the identification of the Am transitions homologous to the strong Eu I transitions from the y/sup 8/P/sub 5/2,7/2,9/2/ terms to the ground state.