Knowledge Bank

The HfF$+$ cation has been identified as a molecule with favorable properties for investigation of the dipole moment of the electron. The ion is predicted to have a $1\Sigma +$ ground state, but the state of greatest interest is the low-lying $3\Delta 1$ state, which correlates with Hf$+$(6s5d)F$-$. A high internal electric field may be generated when the $\Omega$=1 state is polarized by a modest external field. In the present work, spectroscopic data for the ground and low-lying states HfF$+$ have been obtained using the technique of pulse field ionization - zero electron kinetic energy (PFI-ZEKE) spectroscopy. Sequential two-photon excitation was used, with the first photon set to excite a transition near 28593 \wn. This previously unreported band was used as it is at slightly less than half of the ionization energy (IE), and therefore not subject to one-color, two-photon ionization. PFI-ZEKE spectra were recorded for the levels X$1\Sigma +$ (v=0-6), $3\Delta 1$ (v=0-3), $3\Delta 2$ (v=0-3), and $3\Delta 3$ (v=0,1). Rotational resolution was achieved using single rotational line excitation of the intermediate state. The IE for HfF was found to be 59477 \wn. Term energies and molecular constants for the ground and low-lying states of HfF$+$ will be reported.