Molecular Multiphoton Ionization and the "Universal" Short-pulse ATI Spectrum

The ATI electron energy spectra of atoms in the short pulse regime up to intensities of 1014 W/cm2 are now well understood1. Naively applying this understanding of atoms to molecules would lead one to expect molecules to yield a very complex electron energy spectrum due to the multitude of potential curves and vibrational and rotational structure in the molecule. On the contrary, recently obtained ATI electron spectra of nitrogen show a relatively simple structure surprisingly similar to the spectra of atoms (see Fig. 1).