Coster–Kronig decay of the 2s hole state in HCl observed by sub-natural linewidth Auger electron spectroscopy

Threshold photoelectron–Auger electron coincidence spectroscopy has been applied to the Coster–Kronig transitions from the Cl 2s core-hole state of HCl. The use of coincidence spectroscopy reveals Auger lines associated with the Cl 2s core-hole state in the sub-natural linewidth regime. The coincidence Auger spectrum reveals two band structures corresponding to the formation of HCl2+[(Cl 2p)−1 (V)−1] doubly ionized states via Coster–Kronig transitions, which are only weakly observed in the normal Auger spectrum. These structures are tentatively assigned to HCl2+[(Cl 2p)−1 (V)−1] doubly ionized states with the 2π or 5σ valence (V) holes.