Perturbation Parameters for the BaS Molecule

One of the keys to the characterization of an isolated perturbation is a determination of the non-integer J-value, Jx, at which the unperturbed rotational term curves intersect. For a homogeneous perturbation, Jx coincides with the noninteger J-value where the energy separation between the perturbed rotational term curves reaches its minimum value, Jmin- Ignoring centrifugal distortion, 

If the difference between Jx and Jmin is ignored and Jmm is used to extract a value for B or 52, that value will be in error by 01 jAT°. The difference in B° values derived from this incorrect Jx value will be larger than the true A5° by 2/32/ AT°. A least squares fit of a heterogeneous perturbation using the inappropriate homogeneous interaction model will yield deperturbed B°-values shifted from the true values by (32/ AT°. This means that, if an interpolated value of Bc or 52 is known to an accuracy better than /32/ AT° prior to any fit to the perturbed data, then the quality of fit (with one B°-value 

In modern laser experiments, relative intensity measurements have accuracy sufficient to distinguish homogeneous from heterogeneous interactions, even when both main and extra states are bright. 

Perturbation Parameters Interactions Between Valence and Rydberg States of the Same Symmetry 

Most frequently interactions between states of the same electronic symmetry are between a Rydberg state and a valence state and are often referred to in the literature as valence Rydberg mixing. In the following, a distinction is drawn between these two classes of electronic states. 

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