High-resolution electron-momentum spectroscopy of the valence orbitals of the iodine molecule

The valence orbitals of the iodine molecule (I2) have been studied using the high-resolution electron-momentum spectroscopy at impact energies of 1200 and 600 eV. Experimental momentum distributions of outer valence orbitals were compared with the nonrelativistic, scalar relativistic, and spin-orbital relativistic calculations, as well as the relativistic pseudopotential calculation. The experimental cross-section ratios of 8J 3/2 g to 17J 1/2 g , 8J 3/2 u to 16J 1/2 u , and the electron-momentum profiles of orbital 16J 1/2 g clearly manifested the relativistic effects. In the inner valence region, the symmetry-adapted-cluster configuration-interaction theory was used to interpret the ionization spectrum and the electron-momentum distributions.