The Rotationally Resolved Infrared Spectrum of TiO and Its Isotopologues

In this study, we present the ro-vibrationally resolved gas-phase spectrum of the diatomic molecule TiO around 1000\,cm$^{-1}$. Molecules were produced in a laser ablation source by vaporizing a pure titanium sample in the atmosphere of gaseous nitrous oxide. Adiabatically expanded gas, containing TiO, formed a supersonic jet and was probed perpendicularly to its propagation by infrared radiation from quantum cascade lasers. Fundamental bands of $^{46-50}$TiO and vibrational hotbands of $^{48}$TiO are identified and analyzed. In a mass-independent fitting procedure combining the new infrared data with pure rotational and electronic transitions from the literature, a Dunham-like parameterization is obtained. From the present data set, the multi-isotopic analysis allows to determine the spin-rotation coupling constant $\gamma$ and the Born-Oppenheimer correction coefficient $\Delta_{\rm U_{10}}^{\mathrm{Ti}}$ for the first time. The parameter set enables to calculate the Born-Oppenheimer correction coefficients $\Delta_{\rm U_{02}}^{\mathrm{Ti}}$ and $\Delta_{\rm U_{02}}^{\mathrm{O}}$. In addition, the vibrational transition moments for the observed vibrational transitions are reported.