Investigations on the 1_S_0 λ_1→ 1_P^0_1 λ_2→ 1_S_0 nonresonant——→ M+ photoionization pathway for selective ionization of rare calcium and strontium isotopes

Abstract

Optical selectivities have been calculated by use of the density matrix approach for ns2 1S0−nsnp 1P10− nsms (or np2) 1S0 double-resonance photoionization pathways to establish the possibility of selective ionization of rare calcium and strontium isotopes for continuous-wave laser excitation. Numerical integration of the density matrix equations for double-resonance ionization has been carried out by incorporation of the effects of Doppler broadening, velocity-dependent interaction times, time-varying Rabi frequencies, and laser bandwidths. The conditions for obtaining optimum selectivities have been evaluated. This study results in five new photoionization pathways (two for calcium and three for strontium) whose optical selectivities were found to be a few orders higher than the previously studied photoionization schemes. The effect of laser linewidth of the excitation lasers and Doppler width have also been investigated.