Revised molecular constants, RKR potential, and long-range analysis for the B3Π(0 u+) state of Cl 2, and rotationally dependent Franck-Condon factors for Cl 2 ( BX1Σ g+)

Abstract

Literature data for the line frequencies of the B 3Π(0 u +) ← X 1Σ g + transition of Cl 2 are fitted directly by least squares to obtain new molecular constants. The constants from individual bands are merged to obtain single-valued estimates of the rotational constants for each vibrational level of the B state. The results are combined with recent data from the B → X system in emission to obtain new RKR turning points for the B and X states, and Franck-Condon factors for the B- X system. The new constants are also used to provide revised long-range parameters for Cl 2( B) which differ from those of earlier work. In particular, the coefficient C 5 of the leading term in the inverse-power long-range potential is now found to be C 5 = 1.16(2) × 10 5 A ̊ 5 cm −1 . Theoretical results for the variation of centrifugal distortion parameters for levels near dissociation are tested for D v and H v , and an extrapolation based on this behavior is used to facilitate determination of reliable B v and G( v) values for the highest observed B-state levels.