Constant-initial-state spectroscopy of black phosphorus: Reexamination of resonant photoemission

Resonant photoemission in black phosphorus has been reexamined by constant-initial-state (CIS) spectroscopy. The CIS spectra with valence peaks at 2.5 and 10.4 eV as initial states have a clear doublet structure due to the spin-orbit splitting at the 2p core threshold, showing a striking contrast to the earlier study. It has been elucidated that (1) contrary to the earlier report the Fano-type antiresonance does not take place or is undetectably small for the first valence peak at 2.5 eV, and (2) the strong enhancement of the 10.4-eV peak at the 2p core excitation is mainly due to the normal $L_2$,3VV Auger process but not due to the core-exciton-induced Auger process as proposed in the earlier studies.