Radiative transitions in TiO: Ab initio oscillator strengths and lifetimes for low-lying electronic states

Institute für Theoretische Astrophysik der Universität Heidelberg, Tiergartenstraße 15, 69121, Heidelberg, Germany

Corresponding author: N. V. Dobrodey, nickolay@ita.uni-heidelberg.de

Received: 18 August 2000
Accepted: 19 October 2000

Abstract

The dipole transition moments, oscillator strengths and radiative lifetimes for seven low-lying triplet and ten singlet electronic states of the TiO molecule have been calculated using the multireference singles and doubles configuration interaction method (MRCI) and compared with the available literature data. Our MRCI results support the previous theoretical transition moments reported by Langhoff ([CITE]) for the most of the computed bands except for the δ and ϕ ones. For the δ band our computed electronic oscillator strength f_e is 0.0581 which is considerably smaller than that of Langhoff (0.096). Our f_e supports the proposal of Plez ([CITE]) that the value of Langhoff should be divided by ∼2 to match observations. Our MRCI calculations give f_e of 0.0668 for the ϕ band. This is larger than the value of 0.036 obtained by Langhoff. We adduce strong arguments that our f_e for the ϕ band is reasonable. We predict two new and one states which exhibit avoided crossings with the known and states, respectively. These avoided crossings can appreciably perturb the rovibrational levels and, consequently, further complicate the identification of the lines in the experimental spectra. Our calculated transition moments for all the computed electronic states are available at URL http://www.ita.uni-heidelberg.de/research/mld/.