Measurements of photoionization cross sections from the 5s5p 1P1 and 5s6s 1S0 excited states of strontium

We present new measurements of the photoionization cross section from the 5s5p P-1(1) state employing two-step excitation and from the 5s6s S-1(0) state using two-photon excitation and then a second laser for subsequent ionization in each case. The two dye lasers, pumped by a common Nd:YAG laser, have been used in conjunction with a thermionic diode ion detector in one set of experiments and an atomic beam apparatus in the second experiment. The photoionization cross sections have been measured at six different wavelengths between 355 nm and 410 nm. The absolute value of the cross section at the peak of the (4d(2)+5p(2)) D-1(2) autoionizing resonance is determined as 5450 (18%) Mb. The photoionization cross section from the 5s6s S-1(0) state is estimated as 0.41 (16%) Mb.