Photoionization cross section and oscillator strength distribution in the near-threshold region of strontium

We present experimentally measured absolute values of the photoionization cross sections from the 5s5p 1P1 and 5s5p 3P1 excited states of strontium at the first ionization threshold as 11.4±1.8 Mb and 10.7±1.7 Mb respectively using saturated absorption technique along with a thermionic diode ion detector in conjunction with a Nd:YAG pumped dye laser system. These threshold photoionization cross sections values have been utilized to determine the oscillator strengths of the 5s5p 1P1↦5snd 1D2 and 5s5p 3P1↦5snd 3D2 Rydberg transitions. The oscillator strength densities in the continuum corresponding to the 5s5p 3P1 excited state have also been determined by measuring the photoionization cross sections at five ionizing wavelengths above the first ionization threshold. Smooth merging of the discrete f-values into the oscillator strength densities has been observed for the 5s5p 3P1↦5snd 3D2 series across the ionization threshold