The isotope-ratio-enhancement calculations for are carried out using spectral-simulation (SS) and density-matrix (DM) methods for the transition that was considered by YoungShaw [J. Opt. Soc. Am. B 12, 1398–1402 (1995)] a first-step transition in their diode-laser-initiated, resonance-ionization mass spectrometry experiments. The results from the two methods are compared with each other and with the reported experimental result. The SS result is noted to be more sensitive to the residual Doppler width but less sensitive to the laser linewidth than the DM result. It is further noted that under exact correspondence with experimental conditions, the DM result is in much better agreement with the experimental result obtained by Young and Shaw in their two-color resonant, three-photon photoionization of La by use of a narrowband, cw diode laser for the first-step excitation and a broadband, pulsed dye laser for further excitation and ionization.
© 2004 Optical Society of America