Knowledge Bank

The emission spectrum of HfCl has been investigated in the $3000-18500cm-1$ region at high resolution using a Fourier transform spectrometer. The bands were excited in a microwave discharge through a flowing mixture of $HfCl4$ and helium. Two bands near $17140cm-1$ and $17490cm-1$ were also measured in absorption using later excitation spectroscopy. In this instance the molecules were created by laser ablation in a molecular beam apparatus. The observed bands have been classified into electronic transition, [7.6] $\mathrm{<mrow\; data-mjx-texclass="ORD">4</mrow>}\Delta 3/2-X2\Delta 3/2$ and $[17.1]2\Delta 3/2-X2\Delta 3/2$ involving a common lower state. A rational analysis of the 0-0 and 1-1 bands of [7.6]$\mathrm{<mrow\; data-mjx-texclass="ORD">4</mrow>}\Delta 3/2-X2\Delta 3/2$ and 0-0, 1-1 and 1-0 bands of the [17.1]$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Delta 3/2-X2\Delta 3/2$ transitions, has been carried out of the equilibrium spectroscopic constants have been determined. The ground state principal molecular constants are $B=0.1097404(54)cm-1$, $\alpha e=0.0004101(68)cm-1$ and $re=2.290532(57)${\AA}. The ab initio calculations have been performed on HfCl and spectroscopic properties of the low-lying electronic states have been predicted. The ground state is predicted to the regular $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Delta$ state arising from the valence electron configuration, $1\sigma 22\sigma 23\sigma 21\pi 41\delta 1$. On the basis of our ab initio calculations, we assign the observed transitions as $[7.6]4\Delta 3/2-X2\Delta 3/2$ and $[17.1]2\Delta 3/2-X2\Delta 3/2$.