Atomic Lifetimes of Low-Lying Levels in Multiply Charged Ions of Gallium, Germanium, Arsenic, and Selenium

The foil-excitation technique has been used to study atomic lifetimes in multiply charged ions at moderate ion energies (i. e., below 1 MeV). The emission spectra of foil-excited ion beams of gallium, germanium, arsenic, and selenium at 450-keV initial ion energy showed low-lying transitions in Ga II, Ga III, Ge III, Ge IV, As IV, As V, Se V, and Se VI with sufficient spectral intensity for lifetime determinations. In the Cu I sequence, seven lifetimes of transitions in Ga III through Se VI have been measured, while for the Zn I sequence, eight lifetimes of singlet and triplet levels in Ga II through Se V have been reported. Systematic trends in $f$ values for $4s{}_{}{}^2{}_{}{}^{}S-4p{}_{}{}^2{}_{}{}^{}P$ and $4p{}_{}{}^2{}_{}{}^{}P-4d{}_{}{}^2{}_{}{}^{}D$ transitions in the Cu I sequence and for $4s^2{}_{}{}^1{}_{}{}^{}S-4s4p{}_{}{}^1{}_{}{}^{}P$ and $4s4p{}_{}{}^3{}_{}{}^{}P-4s4d{}_{}{}^3{}_{}{}^{}D$ transitions in the Zn I sequence have been studied and compared with similar trends in the Na I and Mg I sequences. Based upon the experimental results, $f$ values for transitions in Br VII through Sr X and Br VI through Sr IX have been found by extrapolation and compared with theoretical and experimental results for homologous atoms with lower masses.