Core and molecular orbital photoelectron spectra of tetraphosphorus and tetraphosphorus trisulfide vapors

The 2s and 2p binding energy shifts in gaseous P4 and P4S3 have been measured relative to the corresponding levels in PF5 and SF6 using AlKα radiation. Theoretical Hartree–Fock and XαSW L-shell orbital energy values are compared with experimental binding energies. The following differential photoelectric cross section ratios were obtained: P2p/P2s, S2p/S2s, S2p/P2p, and S2s/P2s. The cross section computations of Nefedov et al. and Scofield are in fair agreement with our experimental results. In the valence electron region, both AlKα and ZrMζ excitation sources were used, enabling a clear differentiation between the 3s- and the 3p-derived molecular orbitals. The prediction by Head et al. of a 3.48 eV gap between s- and p-like molecular orbitals of P4S3 is supported by the experimental data.