High energy Rydberg and valence states and state interactions of DCl: New observations by mass resolved REMPI

Mass resolved resonance enhanced multiphoton ionization (REMPI) spectra of a mixture of DCl and HCl were recorded for two-photon resonance excitation in the region of 80 500–89 500 cm⁻¹. Spectra due to resonance transitions to rovibrational states of number of Rydberg and ion-pair states of DCl, were identified and assigned. Five new spectral bands due to transitions to Rydberg states and eight new bands due to transitions to vibrational states of the ion-pair state were identified and analysed to derive energetic parameters. Irregularities observed in vibrational energy level spacing, rotational constants and isotope shifts of chlorine isotopologues from what to expect for unperturbed states, as well as relative signal intensities, are indicative of strong homogeneous interaction between the E¹Σ⁺ Rydberg state and the V¹Σ⁺ ion-pair state. These observations are found to be due to level-to-level interaction between E and V rovibrational states of same J′ quantum numbers. Comparison of the data for DCl and HCl is performed.