High-resolution spectroscopy and Ab initio calculations on HfCl

The emission spectrum of HfCl has been investigated in the 3000-18 500 cm(- 1) region at high resolution using a Fourier transform spectrometer. The ba nds were excited in a microwave discharge through a flowing mixture of HfCl 4 and helium. Two bands near 17 140 and 17 390 cm(-1) were also measured in absorption using laser excitation spectroscopy. In this instance the molec ules were created by laser ablation in a molecular beam apparatus. The obse rved bands have been classified into two electronic transitions, [7.6] (4)D elta(3/2)-X(2)Delta(3/2) and [17.1] (2)Delta(3/2)-X(2)Delta(3/2) involving a common lower state. A rotational analysis of the 0-0 and 1-1 bands of [7. 6] (4)Delta(3/2)-X(2)Delta(3/2) and 0-0, 1-1, and 1-0 bands of the [17.1] ( 2)Delta(3/2)-X(2)Delta(3/2) transitions has been carried out and the equili brium spectroscopic constants have been determined. The ground state princi pal molecular constants are B-2 = 0, 1097404(54) cm(-1), alpha(e) = 0.00041 01(53) cm(-1), and r(e) = 2.290532(57) Angstrom. Ab initio calculations hav e been performed on HfCl and spectroscopic properties of the low lying elec tronic states have been predicted. The ground state is predicted to be a re gular (2)Delta state arising from the valence electron configuration, 1 sig ma(2)sigma(2)3 sigma(2)1 pi(4)1 delta(1). On the basis of our nb initio cal culations;. we assign the observed transitions as [7.6](4)Delta(3/2)-X(2)De lta(3/2) and [17.1] (2)Delta(3/2)-X(2)Delta(3/2). (C) 2000 Academic Press.