The D state of I2: a case study of statistical error propagation in the computation of RKR potential curves, spectroscopic constants, and Franck-Condon factors

Existing spectroscopic data for the ion-pair state of I₂ are reanalyzed with the primary goal of improving and extending to higher υ the rotational constants B_υ. To this end, data for several precisely known (υ,J) levels in the υ=203-207 region are analyzed together with vibrational and rotational data from a number of sources. The lack of rotational data for the υ=130-200 region makes the structure of this data set unusual, and has prompted a thorough study of the propagated statistical error in the directly fitted spectroscopic constants, T_υ and B_υ, and in the RKR potential curve calculated therefrom. For the first time, such error propagation computations have been extended to properties computed by numerical solution of the Schrödinger equation for the state in question: the quantum vibrational energy G_υ and rotational constant B_υ, centrifugal distortion constants D_υ and H_υ, and Franck-Condon factors for the D-X transition.