THE MOLECULAR FRAME ELECTRIC DIPOLE MOMENT AND HYPERFINE INTERACTIONS IN HAFNIUM FLUORIDE, HfF

Abstract

The identification of HfF$^{+}$ as a possible candidate for a $\textit{d}_{e}}$ measurement has stimulated new interest in the spectroscopy of both HfF$^{+}$ , \textbf{134}, 201102 (2011).}$^{,}$ , \textbf{546}, 1 (2012).}$^{,}$ , \textbf{272}, 32 (2012).} and neutral HfF $^{a,}$ ,\textbf{276-277}, 49 (2012).}. Studies of the neutral are relevant because photoionization schemes can be used to produce the cations. More importantly, computational methodologies used to predict the electronic wavefunction of HfF$^{+}$ can be effectively assessed by making a comparison of predicted and experimental properties of the neutral, which are more readily determinable. The (1,0)[17.9]2.5 -$\textit{X}^{2}\Delta_{3/2}$ band of hafnium monofluoride (HfF) has been recorded using high-resolution laser-induced fluorescence spectroscopy both field-free and in the presence of a static electric field. The field-free spectra of $^{177}$HfF, $^{179}$HfF, and $^{180}$HfF were model to generate a set of fine and hyperfine parameters for the $\textit{X}^{2}\Delta_{3/2}$ (v=0) and [17.9]2.5 (v=1) states. The observed optical Stark shifts for the $^{180}$HfF isotopologue were analyzed to produce the molecular frame electric dipole moments of 1.66(1)D and 0.419(7)D for the $\textit{X}^{2}\Delta_{3/2}$ and [17.9]2.5 states, respectively. A two-step $\textit{ab initio}$ calculation consisting of a two-component generalized relativistic effective core potential calculation (GRECP) followed by a restoration of the proper four-component wavefunction was performed to predict the properties of ground state HfF.