ISOTOPE SHIFTS OF ZN NEUTRAL ATOMS MEASURED BY 2-PHOTON DOPPLER-FREE LASER-INDUCED FLUORESCENCE SPECTROSCOPY

Two-photon Doppler-free laser-induced fluorescence spectroscopy has been used for the first time to measure isotope shifts between the three most abundant stable isotopes of zinc (64, 66 and 68). A high-resolution laser system, consisting of an argon ion-pumped cw ring dye laser, a three-stage pulsed amplifier chain, and a doubling crystal, was used to generate tunable uv radiation for the experiment. Gas-phase Zn atoms were generated by laser-ablating a ZnS crystal. The Doppler-free spectrum was produced for the two-photon allowed 4s2 1S0-4d1D2 transition (λ = 160 nm) of Zn by reflecting the laser beam back on itself. The measured isotope shifts were 976 ± 39 MHz for 64Zn-66Zn and 888 ± 24 MHz for 66Zn-68Zn. The technique of producing counter-propagating light by back-reflecting the laser beam has been used in situ to determine both the zero velocity frequency of particles in Doppler-shifted velocity distribution experiments and to measure the bandwidth of frequency-doubled laser light. © 1990 Pergamon Press plc.