OPTIMAL SCHEMES OF RESONANT PHOTOIONIZATION OF LEAD ATOMS

Energies of over 60 Rydberg 6snp-states of lead atoms were measured by means of two-step laser excitation with subsequent ionization by an e lectric field. The intermediate level from which Rydberg states were e xcited was 6p7s(1/2, 1/2)(1) (E= 35287.2244 cm(-1)). Among the measure d states several states belonging to the 4 Rydberg series were isolate d: 6pnp(1/2, 1\2)(0) (n=18-30) 6pnp(1/2, 3/2)(1) (n=18-22), 6pnp(1/2, 3/2)(2) (n=18-53) and 6pnp 1/2[5/2](2) (n=15-27). The accuracy of such measurements was 0.5 cm(-1). Optimal schemes of resonant photoionizat ion of lead atoms through Rydberg states were chosen on the basis of t he results obtained for highly excited states. Recommendations were el aborated to ensure accurate measurements and high sensitivity in detec ting lead traces by resonant ionization spectroscopy. The sensitivity obtained for lead reached a value of 10 ng/ml and was limited by pollu tion of the environment with lead traces. The ultimate sensitivity of the used technique for lead was estimated at 0.125 ng/ml.