Atomic and molecular 2p binding energies of P, As, and Se from many-body calculations and x-ray photoelectron spectroscopy

The 2p12,32 levels in As4 and the 2p32 level in Se5,6 have been measured by x-ray photoelectron spectroscopy with the use of 1486.6-eV (AlK) radiation. The 2p12 binding energies have been calculated for the atomic species, as well as for atomic phosphorus, as the difference between the total energies of the 2p12 hole state and the ground (neutral) state SCF (self-consistent field method), using the Dirac-Fock program of Desclaux, to which is added the respective correlation-energy difference between the two states. The calculated values of 140.70 eV for P2p12, 1368.89 eV for As2p12, and 1484.88 eV for Se2p12 include a 0.7-1.0-eV increase due to the effects of correlation, consistent with earlier work done on the K and Zn atoms. The 2p32 atomic binding energies were calculated similarly with the use of available Dirac-Slater SCF values. When we combine these with the measured molecular binding energy of P4, As4, and Se5,6 we obtain corresponding 2p chemical shifts (atom-molecule) of 3.5, 3.0, and 2.4 eV, respectively. Comparison is also made between the atomic, molecular, and solid-state binding energies of As and Se, and it is found that the solid-state binding energy is the lowest of the three in both cases, as expected from consideration of extra-atomic relaxation. © 1983 The American Physical Society