Theoretical study of the excited and continuum states in the NEXAFS regions of Cl2

The NEXAFS regions of Cl-2 near the 2p and 1s core thresholds have been theoretically considered. The electron excitations below the ionization limit have been treated with a highly correlated ab initio method (QDPT-CI). The position of doubly excited states above Is ionization has also been considered at the CI level. The region above the threshold is described with an explicit continuum method, based on a LCAO formalism within the framework of density functional theory. The results are in very good accordance with the experiment and support detailed assignment of the spectral feature. Comparison of the present results with respect to previous work on HCl shows a more atomic behaviour of Cl-2 with respect to HCl below edge and the opposite in the continuum. The former is traced to the stronger chemical bond in HCl, the second to the larger relaxation of Cl-2 in the ionic state.