The TiOc1Φ–a1Δ (0–0) Band at Sub-Doppler Spectral Resolution: Spin–Orbit Interactions in thecState

Abstract

Thec1Φ–a1Δ (0–0) band of titanium monoxide has been studied at sub-Doppler resolution by crossing a beam of TiO molecules with a cw tunable laser beam and collecting the laser-induced fluorescence. The rotational structures of theP,Q, andRbranches have been observed up to rotational quantum numbers equal to 52, 94, and 96, respectively. The spectroscopic data have been reduced to a set of 11 effective molecular constants with a root mean squared values of the residuals equal to 7 × 10−4cm−1. However, the necessity of including seventh order terms in the rotational development of the energy put into evidence a very strong spin–orbit interaction between thec1Φ (v= 0) andC3Δ3(v= 2 andv= 3) levels. The derived spin–orbit parameter allows for the reproduction of the measured wavenumbers without the introduction of higher order rotational terms into the energy development. The value of the spin–orbit parameter indicates the necessity of revisiting the configuration scheme of the involved electronic states.