High-resolution inner-valence UV photoelectron spectra of the O2 molecule and CI calculations of 2IIu states between 20 and 26 eV

摘要

High resolution HeI and HeII excited inner valence photoelectron spectra of the oxygen molecule have been recorded between 20 and 26 eV. In this range, three photoelectron bands are clearly seen; they are associated with the B $+2$/$Sigma$-g$/$+$MIN$/,3 $+2$/$PI$-u$/ and c $+4$/$Sigma$-u$/$+$MIN$/ states of O$- 2$/$+$PLU$/. The state of $+2$/$PI$-u$/ symmetry observed around 24 eV shows a long vibrational progression, contrary to earlier work, with spacings that decrease successively toward higher electron binding energies. The assignment is confirmed by ab initio calculations. These calculations show that if the potential curve is followed along the electron configuration rather than the adiabatic curve, the vibrational structure can be accounted for.