Shifting and broadening in the fundamental band of CO highly diluted in Heand Ar: A comparison with theory

We present measurements of the shifts and widths of the rovibrational lines of the fundamental band of CO highly diluted in He and Ar at 296 K. The sh ifts are decomposed into parts odd and even in the line number, m. These ar e then compared with close coupled calculations carried out with the best k nown interaction potentials. There is general agreement between the calcula ted and measured values of the broadening and shifting. Furthermore, the re sults illustrate that the decomposition of the shifts into parts, odd and e ven in m, is a powerful tool for separating out the relative contributions of the isotropic and anisotropic part of the interaction to the shifts and which part needs to be corrected if there is a discrepancy. Thus, shift mea surements can be added to the list of experiments that may be used to deter mine reliable interaction potentials. The results also show, given a potent ial, that close coupled calculations are accurate and could be used to conf irm or establish empirical models of the temperature dependence of the broa dening or shifting, etc. Such modeling is important at atmospheric physics. (C) 2001 American Institute of Physics.