Oscillator Strengths and Predissociation Rates for Rydberg Transitions in12C16O,13C16O, and13C18O Involving theE1Π,B1Σ+, andW1Π States

One of the processes controlling the interstellar CO abundance and the ratioof its isotopologues is photodissociation. Accurate oscillator strengths andpredissociation rates for Rydberg transitions are needed for modeling thisprocess. We present results on absorption from the E ^1Pi-X ^1Sigma^+ (1-0) andB ^1Sigma^+-X ^1Sigma^+ (6-0) bands at 1051 and 1002 \AA, respectively, and thevibrational progression W ^1Pi-X ^1Sigma^+ (v'-0) bands with v' = 0 to 3 at972, 956, 941, and 925 \AA, respectively. The corresponding spectra wereacquired at the high resolution (R ~ 30,000) SU5 beam line at the Super ACOSynchrotron in Orsay, France. Spectra were obtained for the ^12C^16O, ^13C^16O,and ^13C^18O isotopologues. These represent the most complete set ofmeasurements available. Comparison is made with earlier results, both empiricaland theoretical. While earlier determinations of oscillator strengths based onabsorption from synchrotron radiation tend to be somewhat smaller than ours,the suite of measurements from a variety of techniques agree for the most partconsidering the mutual uncertainties. For the bands studied here, theirrelative weakness, or their significant line widths arising frompredissociation, minimizes potential problems from large optical depths at linecenter in absorption measurements. Predissociating line widths could generallybe extracted from the spectra thanks to the profile simulations used in theanalysis. In many cases, these simulations allowed us to consider e and fparity levels separately and to determine the dependence of the width onrotational quantum number, J. Our results are consistent with earlierdeterminations, especially the widths inferred from laser experiments