An Analysis of the $B^{3}\Pi _{2} - X^{3}\Delta _{2}$ (0, 0) Band System of the TiO Molecule in Laboratory and Sunspot Spectra

Abstract

The $B^{3}\Pi _{2} - X^{3}\Delta _{2}$ (0, 0) band system of the titanium monoxide (TiO) molecule was excited in a DC copper arc with a constant deviation spectrometer. The resulting spectrum has been analyzed using image J software. Relative intensity measurements of the P- and R-branch molecular lines of the (0, 0) band with rotational quantum ($J$) numbering have been obtained. The measured intensity of rotational molecular lines and the $J$ numbering were used to estimate the excitation rotational temperature of the source emitting the spectrum of TiO molecules. Also the presence of TiO spectral lines of the $B^{3}\Pi _{2} - X^{3}\Delta _{2}$ (0, 0) band in the wavenumber region of 14 500 to 16 000 cm⁻¹ has been confirmed in the umbral spectrum, from the atlases recorded at the National Solar Observatory using the Fourier transform spectrometer (FTS) of the McMath-Pierce Solar Telescope on Kitt Peak. The combined laboratory and sunspot spectral line measurements have been used to obtain the improved molecular structure parameters for the electronic states $B^{3}\Pi _{2}$ and $X^{3}\Delta _{2}$ of the TiO molecule. Using equivalent width measurements of well resolved and identified lines in the sunspot spectrum with known rotational quantum number, the effective rotational temperature was found to be $2555 \pm 780$ K. This proves the presence of TiO molecules in sunspot and other higher temperature astrophysical sources.