High resolution rotational analysis of the B 3Π–X 3Δ (1,0) band of titanium monoxide

The B 3Π–X 3Δ (1,0) band of titanium monoxide has been studied at sub-Doppler resolution (0.002 cm−1) by crossing a beam of TiO molecules with a cw tunable laser beam and by collecting the laser-induced fluorescence. The rotational structure of 42 branches belonging to the 3Π–3Δ transition has been analyzed up to rotational quantum numbers equal to 94. Spectroscopic data have been reduced to a set of 24 molecular constants, using a case (a) effective Hamiltonian. The rotational, spin–orbit and Λ-doubling constants are discussed in terms of the leading configurations which give rise to the X 3Δ and B 3Π electronic states. It is shown that for the B state, existing ab initio calculations are not able to reproduce the second order spin–orbit effect and the Λ doubling effect.