REMPI spectroscopy of HfF

Abstract

The spectrum of electronic states at 30 000–33 000 cm[superscript −1] in hafnium fluoride has been studied using (1 + 1) resonance-enhanced multi-photon ionization (REMPI) and (1+1[superscript ′]) REMPI. Six Ω[superscript ′] = 3/2 and ten Π[subscript 1/2] vibronic bands have been characterized. We report the molecular constants for these bands and estimate the electronic energies of the excited states using a correction derived from the observed isotope shifts. When either of two closely spaced Π[subscript 1/2] electronic states is used as an intermediate state to access autoionizing Rydberg levels, qualitatively distinct autoionization spectra are observed. The intermediate state-specificity of the autoionization spectra bodes well for the possibility of using a selected Π[subscript 1/2] state as an intermediate state to create ionic HfF[superscript +] in various selected quantum states, an important requirement for our electron electric dipole moment (eEDM) search in HfF[superscript +].