A direct approach for the reduction of diatomic spectra to molecular constants for the construction of RKR potentials

• Published in: Journal of molecular spectroscopy Vol. 46; no. 1; pp. 37 - 66
• Main Authors: Zare, R.N., Schmeltekopf, A.L., Harrop, W.J., Albritton, D.L.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.01.1973
• ISSN: 0022-2852; 1096-083X
• DOI: 10.1016/0022-2852(73)90025-8

A nonlinear fitting procedure is presented that employs all measured line positions and iteratively compares their values with those calculated from numerically diagonalized model Hamiltonians with adjustable molecular constants. Case (a) wavefunctions with definite parity are introduced as a convenient basis set, and the effects of spin-orbit, spin-spin, spin-rotation, and centrifugal distortion interactions neglected in the Born-Oppenheimer separation are included simultaneously using the Van Vleck transformation. The spectroscopic constants found by this procedure represent the minimum-variance, unbiased set and maintain, to a high degree of accuracy, the separate mechanical and magnetic meanings of the molecular constants. Arguments are presented that such spectroscopic constants with mechanical meaning allow the most accurate construction of potential energy functions using the Rydberg-Klein-Rees (RKR) procedure. Residual mechanical and magnetic ambiguities, such as engendered by Λ-type doubling, are discussed.