IMPROVED DUNHAM COEFFICIENTS FOR CO FROM INFRARED SOLAR LINES OF HIGH ROTATIONAL-EXCITATION

About 4500 unblended CO lines have been selected and their wavenumbers accurately measured on high resolution solar spectra obtained from space with the ATMOS Fourier transform spectrometer. Half of these lines are of high rotational excitation energy and have never been observed before in the laboratory. Line positions of the fundamental bands of 12C16O have been measured up to J = 133, those of 13C16O and of 12C18O up to J = 103 and 91, respectively. The first overtone bands of 12C16O have been measured up to J = 110. These new solar CO wavenumbers, with an additional selected set of about 14 000 accurate laboratory measurements, have been simultaneously fitted to the Dunham expression utilizing 10 recently published relations between isotopically invariant parameters Uij. The present set of coefficients reproduces all accurate laboratory positions and our solar measurements of high rotational excitation with a standard deviation of about 10-5 cm-1 (300kHz). This new set is particularly recommended for all high resolution studies of infrared laboratory and stellar spectra showing CO lines of high J-values. © 1991.