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

The dipole transition moments, oscillator strengths and radiative lifetimes for seven low-lying triplet and ten singlet electronic states of the TiO m olecule have been calculated using the multireference singles and doubles c onfiguration interaction method (MRCI) and compared with the available lite rature data. Our MRCI results support the previous theoretical transition m oments reported by Langhoff (1997) for the most of the computed bands excep t for the delta and phi ones. For the delta band our computed electronic os cillator strength f(0) is 0.0581 which is considerably smaller than that of Langhoff (0.096). Our f(e) supports the proposal of Plez (1998) that the v alue of Langhoff should be divided by similar to2 to match observations. Ou r MRCI calculations give fa of 0.0668 for the phi band. This is larger than the value of 0.036 obtained by Langhoff. We adduce strong arguments that o ur f, for the phi band is reasonable. We predict two new (1)Pi and one (1)P hi states which exhibit avoided crossings with the known b(1)Pi and c(1)Phi states, respectively. These avoided crossings can appreciably perturb the rovibrational levels and, consequently, further complicate the identificati on of the lines in the experimental spectra. Our calculated transition mome nts for all the computed electronic states are available at URL http://www. ita.uni-heidelberg.de/rssearch/mld/.