Spin–orbit autoionization and intensities in the double-resonant delayed pulsed-field threshold photoionization of HCl

State‐selected delayed pulsed‐field threshold photoionizationspectra of HCl and DCl are recorded in double‐resonant transitions through the F ^1Δ, E ^1Σ^+, and g ^3Σ^− states of the 4pπ Rydberg configuration. Comparison of observed rotational line strengths with calculated spectra, as well as with available time‐of‐flight photoelectron spectra, provides useful insight on the influence of spin–orbit and rotational autoionization on delayed pulsed‐field threshold photoionization of HCl. Spin–orbit and rotational autoionization are seen to dramatically reduce the ion rotational intensity associated with the upper spin–orbit level of the ion