Radiative lifetimes of the low-lying electronic states of CuF and CuCl: Identification of the excited states of CuCl

Theoretical characterization of the low-lying excited states of the CuCl molecule

“…In Table V we present the CASSCF, CASPT2(v), and CASPT2(c -v) vertical de-excitation energies, calculated at the equilibrium distances of each excited state ͓i.e., the CASPT2(c -v) values as shown in Table IV͔ 21,23 The results obtained for the adiabatic transitions are not reported but they are quite close to the vertical ones. This is because the equilibrium distances for all states are essentially the same.…”

“…The 3 ⌸ and 1 ⌸ states are well described; thus the two bands appearing around 20 000 cm Ϫ1 , the B and C bands, are assigned to different spin-orbit components of the 3 ⌸ state, as suggested by Delaval et al 21,23 and Winter et al 22 The 3 ⌺ ϩ →X 1 ⌺ ϩ transition appears around 17 700 cm Ϫ1 and it is more likely to correspond to the A band observed around 19 000 cm Ϫ1 than to the A around 13 500 cm Ϫ1 proposed by Balfour et al 18 The influence of the relativistic effects in this band is shown to be rather small. Thus, we believe that the 3 ⌺ ϩ →X 1 ⌺ ϩ transition corresponds to the experimentally reported A band since there is not any physical mechanism which could explain the much lower A excitation.…”

“…21 The only dipole allowed transitions within the BornOppenheimer approximation correspond to 1 ⌺ ϩ →X 1 ⌺ ϩ and 1 ⌸→X 1 ⌺ ϩ , thus the triplet-singlet transitions, which are allowed due to spin-orbit coupling, show generally smaller intensities than the allowed singlet-singlet ones. 23 From the experimental data it seems that the position of the bands is well defined, but the discussion above illustrates that the assignment of these bands to the different excitations is still not well defined.…”

“…21,22 The characterization and assignment of the AЈ band in CuCl seems unclear and is still an open question since several attempts to find it via laser spectroscopy have failed. 21 Recently, Delaval et al 21,23 made a study of the radiative lifetimes in CuCl and made a comparison with the well established results in the CuF molecule. These authors found the B and C states to correspond to the 3 ⌸ 1 and 3 ⌸ 0 components of the 3d-hole 3 ⌸ state, the D and E states are the 1 ⌸ and the 1 ⌺ ϩ 3d-hole states, respectively, and the F system corresponds to the 3 ⌬ 1 component.…”

“…These authors found the B and C states to correspond to the 3 ⌸ 1 and 3 ⌸ 0 components of the 3d-hole 3 ⌸ state, the D and E states are the 1 ⌸ and the 1 ⌺ ϩ 3d-hole states, respectively, and the F system corresponds to the 3 ⌬ 1 component. The A system was first assigned to the 3 ⌸ 2 component of the 3d-hole 3 ⌸ state, 23 and later reassigned to the ⍀ ϭ 1 component of 3 ⌺ ϩ . 21 The only dipole allowed transitions within the BornOppenheimer approximation correspond to 1 ⌺ ϩ →X 1 ⌺ ϩ and 1 ⌸→X 1 ⌺ ϩ , thus the triplet-singlet transitions, which are allowed due to spin-orbit coupling, show generally smaller intensities than the allowed singlet-singlet ones.…”