Ionization of strontium atoms by ultrashort pulses of a Ti-Sapphire laser

We present experimental photoelectron spectra obtained by ionizing two-valence electron Sr atoms with ≈25 fs Ti- Sapphire laser pulses and we show preliminary evidence that electron-electron correlation effects dominate for laser intensities <0.4×1013 W-cm-2, while a single electron picture prevails when the laser intensity is increased further.