We report spectroscopic studies of the zinc plasma produced in air by the three harmonics of a Q-switched pulsed Nd : YAG laser at 1064, 532 and 355 nm. The electron temperature has been determined from the intensity ratio of the transitions (4s4d 3D3 → 4s4p 3P2) at 334.5 nm and (4s5s 3S1 → 4s4p 3P2) at 481.0 nm of neutral zinc, whereas the electron number density has been evaluated from the Stark broadening of the (4s4d 3D3 → 4s4p 3P2) transition at 334.5 nm. It is observed that both these parameters decrease as the distance from the target surface increases and it increases with an increase in the laser irradiance. The power law is fitted to the experimental data.

New high resolution observations of the 2p inner-shell and of the doubly exciled stales of sodium covering the spectral region 3 2 W 0 0 h are reported. The speclra were worded in the firs1 order of a three-metre spectrograph equipped with a 5000 linelmm holographic &ng, using synchrotron radiation emitted by the 500 MeV eledron accelerator as the background source of radiation. More than 200 new levels of Na I are reported, which are interpreled as inner-shell transitions. 2pS3s('P~.~.u,'P~)ns. nd and the doubly excited 2ps3pnt, 2p53dne and 2p54sne transitions. All the observed levels lie well above the first ionizafion threshold and are arranged into Rydberg series converging onto fifteen conspicuous limits. The inter-channel interactions bemeen the overlapping series have been parameterized using multichannel quantum defect theory.

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Lithium isotope separation has been achieved employing the two-step photoionization technique along with a narrow band dye laser in conjunction with a time of flight mass spectrometer. The demonstrated method yields a high degree of selectivity by tuning the dye laser at the resonance levels of Li6 and Li7. It is inferred that the concentration of the natural abundance of the Li6 isotope gets enhanced up to over 47% as the exciter dye laser is tuned to the P1∕22 of Li6 even if the linewidth of the exciter laser is not sufficiently narrow to excite the isotopic level. It is also noticed that the much higher energy density of the exciter laser limits the resolution of the fine structure levels of the lithium isotopes that leads to a loss in the enrichment of Li6 due to the power-broadening effect. Measurements of the photoionization cross section of the lithium isotopes from the 2pP1∕2,3∕22, excited states for Li6 and Li7 and the corresponding number densities are reported.

New observations of the 5p spectra of Cs i and Ba i are reported. The extreme complexity of the structure does not permit precise configuration labels to be attached to all the excited levels. Nevertheless, more than 160 transitions in Ba i have been ordered into 14 series converging on experimentally known levels of the parent ion. An attempt has been made to analyse the limit structure by comparison with the data for Cs I and Hartree-Fock atomic structure calculations. The results obtained are consistent with previous interpretations of the double ionization anomaly in Ba I. Further comments are made on the comparison between experiment and the predictions of the r.p.a.e. theory for 5p excitation in Ba i. It is shown that the 5p 6 6s 2 S 1/2 -> 5p 5 6s 2 2 P 1/2 and 2 P 3/2 transitions of Cs i have been incorrectly identified and new assignments are proposed.