PNNL

Abstract

Lineshapes in high-resolution triple-resonance ionization spectroscopy have been calculated and compared with experimental measurements on the 4s2 1S0 --- 4s4p 1P1 --- 4s4d 1D2 --- 4snf 1F3 --- Ca+ system of calcium. Calculations based on the density matrix formalism integrated the fundamental equations over experimental atomic angular and velocity distributions and laser intensity profiles. The measurements reveal and confirm all predicted structures arising from the complex coupling of four atomic states with three laser fields and the Doppler distribution of the atomic ensemble. Effects of different laser beam geometries on the lineshapes have been investigated. The agreement between calculated and experimental spectra is generally good over a dynamic range of 10 orders of magnitude. Thus, these calculations are able to accurately predict optical isotopic selectivity in multi-step resonance ionization, with a value of Sopt~1010 expected for detection of the ultra-trace isotope 41Ca.