Knowledge Bank

The electronic emission spectra of HfH and HfD were investigated in the 476 nm to 1 $\mu$ spectral region using a Fourier transform spectrometer. The bands were excited in a hafnium hollow cathode lamp in the presence of a mixture of neon and $H2$ of $D2$ For HfH two $\Delta \Omega =0$ electronic transitions with a common $\Omega \prime \prime =3/2$ lower state, most probably the $X2\Delta 3/2$ ground state, were identified at $14495cm-1$ and $19147cm-1$. These bands have been assigned as the $[14.5]3/2-X2\Delta 3/2$ and the $[19.1]-X2\Delta 3/2$ transitions. The rotational analysis of the 0-0 and 1-1 bands of the $[14.5]3/2-X2\Delta 3/2$ system and the 0-0 band of the $[19.1]3/2-X2\Delta 3/2$ system provides the following equilibrium constants for the ground state of HfH: [ B_{e}{^{\prime\prime}} = 5.01911(8) cm^{-1}, \alpha_{e}{^{\prime\prime}} = 0. 12026(11)\ cm^{-1} \ { and} \ r_{e}{^{\prime\prime}} = 1. 830691(15) \textrm{\AA}. ] For HfH only the 0-0 band of the $[19.1]3/2-X2\Delta 3/2$ transition at $19134cm-1$ was identified. This work represents the first observation of the HfH and the HfD molecules.