Theoretical study of the scandium and yttrium halides

Publisher Website
Google Scholar
Abstract
Theoretical spectroscopic constants are reported for the X 1Σ+ and a 3Δ states of the fluorides, chlorides, and bromides of scandium and yttrium. The calculated D0 values (eV) are ScF(6.00), ScC1(4.55), ScBr(3.90), YF(6.72), YC1(5.36), and YBr(4.74). All systems are predicted to have 1Σ+ ground states once the effect of unlinked higher excitations are incorporated using the coupled‐pair functional approach and relativistic effects are included using either perturbation theory or relativistic effective core potentials. The singlet–triplet splitting is larger for the yttrium halides and decreases for both metals from F to Br. A complete‐active space self‐consistent‐field plus multireference configuration‐interaction study of the spectroscopic constants and radiative lifetimes is presented for most of the singlet and triplet states of ScF and YCl below 28 000 cm−1. The theoretical Te value computed for the B 1Π state of ScF indicates that the longest wavelength peak (9405 Å) for the B 1Π←X 1Σ+ system observed in absorption in a neon matrix probably corresponds to the 2–0 band. The calculations provide an unambiguous assignment of two previously unassigned band systems in the laser excitation spectrum of the YCl molecule.