Electron spectroscopy of molecules in intense laser fields

Electron energy spectra are presented for simple molecules (N2,O2 and CO2) in intense laser fields by the linearly and circularly polarized femtosecond laser pulses. From the comparison of these spectra with rare gas atoms at similar ionization energies, it is shown that the difference of the spectral pattern reflects the character of the outermost valence molecular orbital from which the electron is emitted. Angular distributions of high-energy electron spectra in the rescattering region are also observed for several rare gas atoms (Ne, Ar, and Xe) and molecules (N2 and O2). We demonstrated that the structural information, in particular the differential cross sections of the target ion by free electrons, can be extracted from the electron yields along the outermost ridges of the spectra.