Global Multi-isotopologue fit of measured rotation and vibration-rotation line positions of CO in X1Σ+ state and new set of mass-independent Dunham coefficients

A set of mass-independent Umj and Δmj parameters globally describing vibration-rotation energy levels of the CO molecule in the X1Σ+ ground electronic state was fitted to more than 19,000 transitions of 12C16O, 13C16O, 14C16O, 12C17O, 13C17O, 12C18O, and 13C18O isotopologues collected from the literature. The maximal values of the vibrational V and the rotational J quantum numbers included in the fit was 41 and 128, respectively. The weighted standard deviation of the fit is .66. Fitted parameters were used for calculation of Dunham coefficients Ymj for nine isotopologues 12C16O, 13C16O, 14C16O, 12C17O, 13C17O, 14C17O, 12C18O, 13C18O, and 14C18O. Calculated transition frequencies based on the fitted parameters were compared with previously reported. A critical analysis of the CO HITRAN and HITEMP data is also presented.