NUMERICAL-STUDIES OF THE ISOMER SELECTIVITY OF 2-STEP AND 3-STEP RESONANCE IONIZATION OF NIOBIUM

Through numerical simulations in the density-matrix and amplitude form alisms, we study the isomer selectivity of a double-and triple-resonan ce ionization scheme of niobium (Nb). The energy-level model comprises three or four hyperfine doublets with the magnetic substates incorpor ated. The model parameters (hyperfine splittings, level decay rates) a re chosen to imitate accurately a particular excitation scheme of Nb. The doublets are coupled by pulsed multimode fields. The field fluctua tions are modeled through random, abrupt jumps in the values of the fi eld parameters (phases, amplitudes, frequencies). The isomer selectivi ty is computed in different noise scenarios, and the effect of small ( less than or equal to 300 MHz) isotope shifts on the selectivity is st udied.