Photo-double ionization of deuterium chloride studied by threshold photoelectrons coincidence spectroscopy

Photo-double ionization of DCl has been investigated in the 35.5–38 eV energy range using synchrotron radiation on beamline 10.0.1.2 of the Advanced Light Source by the threshold photoelectrons coincidence (TPEsCO) method. The TPEsCO spectrum of DCl, encompassing the formation of the ground (X 3Σ−) and first-excited (a 1Δ) states of DCl2+, was recorded at good resolution (∼13 meV) using a pair of penetrating-field electron spectrometers. Four vibrational bands were identified in both electronic-state systems. In addition, the threshold photoelectron (TPE) spectrum of DCl for the formation of singly-charged DCl was recorded simultaneously in the same energy range. Indirect resonance autoionization of Rydberg ion states appears to play a substantial role in the formation of the (X 3Σ−) state of DCl2+ while the (a 1Δ) state appears to be formed primarily by direct photo-double ionization.