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 Å were measured using Am-metal vapor. The metallic Am was obtained by reducing ${\mathrm{AmO}}_2$ with La at 1500 °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 °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^8$$P_{5/2}$,7/2,9/2 terms to the ground state.

• Received 2 May 1988

DOI:https://doi.org/10.1103/PhysRevA.38.5084