LASER-INDUCED ISOTOPIC EFFECTS IN TITANIUM RESONANCE IONIZATION

Titanium isotope ratios have been measured by resonance ionization mas s spectrometry (RIMS) with special emphasis on the nature of laser-ind uced isotopic selectivity. A pronounced wavelength dependence of even mass isotope ratios is caused by large nuclear volume effects near the magic neutron number 28 in Ti-50. Optical isotope shifts, ranging fro m 0.07 to 0.21 cm-1, between Ti-50 and Ti-46 were measured for several transitions. The Ti-50/Ti-46 and Ti-48/Ti-46 ratios, nevertheless, ex hibited only mass-dependent fractionation, in which the lighter Ti iso topes were enriched by approximately 2.5%/amu, when the laser operatin g parameters were properly controlled. Odd-even mass isotopic selectiv ity in the resonant ionization process was also examined for several t ransitions as a function of the laser polarization state and intensity . Under saturating conditions for a DELTAJ = + 1 transition and a high degree of laser depolarization for a DELTAJ = 0 transition, the odd-e ven isotopic enhancement was reduced below the 2% level. The Ti isotop e data agree with our previous results for Os and indicate that, by a careful choice of resonance transitions and laser operating parameters , isotope ratios can be measured accurately and reliably with RIMS.