Electron Spectroscopy of strontium in the vicinity of four-photon excitation of the 5p2 1S0 state

We present experimental photoelectron energy spectra and angular distributions from multiphoton ionization of Sr by dye laser pulses of ~ns duration in the wavelength range of 715-737 nm and relatively low intensity (≈4×1011 Wcm-2). The selected wavelength range comprises the highly correlated 5p2 1S0 autoionizing state, excited by four photons. Our results reveal the dominant (single and double) ionization pathways that were obscured in earlier experiments, based solely on the recording of ion and ionic-fluorescence yields.