Two-step photoionisation of palladium

The efficiency of two-step ionisation of palladium involving the 276.4-nm 4d^{10 1}S₀ – 4d⁹5p³P₁ transition is measured as a function of the laser radiation intensity in experiments aimed at laser separation of isotopes. It is shown that to obtain the efficient (over 50%) two-step ionisation of palladium by 10-ns laser pulses with a pulse repetition rate of 10 kHz, an average radiation intensity should exceed 100 W cm^-2. The results of comparison of theoretical and experimental data on the two-step ionisation efficiency make it possible to estimate the photoionisation cross section of the 4d⁹5p³P₁ state (σ_i ≈ 10^-16 cm²).