Rydberg and ion-pair states of HBr: New REMPI observations and analysis

► Ion mass spectra as a function of two-photon wavenumber were recorded for HBr. ► New spectra due to transitions to Rydberg states are observed and characterized. ► New spectra due to transitions to ion-pair states are observed and characterized. ► First observations of n = 6 Rydberg states, by REMPI, are reported. ► State interactions, showing as line shifts and intensity alterations, are shown to be useful in spectra assignments.