Electronic spectra and response properties of BH and AlH

We have calculated ground-state potential-energy curves, vertical electronic excitation energies, transition moments, radiative lifetimes, and indirect nulcear spin–spin coupling constants of BH and AlH. The coupling constants are predicted to be J(11B–H)=49.40 Hz and J(27Al–H)=10.01 Hz. Total energies are obtained using the coupled clusters singles and doubles method while excitation energies and response properties are calculated by means of the coupled cluster polarization propagator method. It is essential for the agreement with experiment that the coupled cluster rather than the second-order polarization propagator method is applied. The lowest excitation energies of each symmetry are nearly the same in a CISD (CI singles and doubles) calculation as in the polarization propagator calculation and both methods agree well with experiment. However, orbitals optimized for the individual states are needed in the CISD calculation, whereas ground-state self-consistent field (SCF) orbitals may be used for all states in the propagator calculation.