# DIRECT POTENTIAL FIT ANALYSIS OF EMISSION INTO $X {^{1}}\Sigma^{+}_{g}$ STATE $Rb_{2}$: NOTHING ELSE WILL DOI

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 Title: DIRECT POTENTIAL FIT ANALYSIS OF EMISSION INTO $X {^{1}}\Sigma^{+}_{g}$ STATE $Rb_{2}$: NOTHING ELSE WILL DOI Creators: Seto, Jenning Y.; Le Roy, Robert J.; Vergès, J.; Amiot, C. Issue Date: 1999 Publisher: Ohio State University Abstract: High resolution $A-X$ emission data involving ground state levels up to $v^{\prime \prime} = 111$ (spanning 99.5\% of the potential well) have been acquired for three isotopomers of $Rb_{2}$ in the ground electronic state. While a good fit $(\bar{\sigma}_{f} = 1.18)$ to the 12144 transition frequencies (with uncertainties $\pm 0.001 cm^{-1})$ is obtained from an unconstrained combined-isotopomer Dunham-type analysis, it requires a large number (66) of expansion parameters, and resulting unconstrained centrifugal distortion constants (CDC's) will be unreliable for extrapolations to higher-J. Moreover, Dunham or near-dissociation expansion fits using constrained theoretical CDC's up to $O_{v}$ fail to properly represent the data, as even higher-order CDC's are required. In contrast, a direct fit of these data to a Modified Lennard-Jones'' analytical $potential^{a}$ defined by only 15 fitted parameters yields essentially the same standard error as the unconstrained Dunham fit, and should yield reliable predictions for essentially all J's. This potential form incorporates the proper $R^{-6}$ asymptotic behaviour and is constrained to have the theoretically predicted $C_{6}$ dispersion $coefficient.^{a}$ Although the data set involves the three isotopomers (85,85), (85,87) and (87,87), none of these analyses were able to determine any Born-Oppenheimer Breakdown effects. Description: $^{a}$ P.G. Hajigeorgiou and R.J. Le Roy, Paper WE04 at the 49'th Ohio State University International Symposium on Molecular Spectroscopy, 1994 Author Institution: Guelph-Waterloo Centre for Graduate Work in Chemistry and Biochemistry, University of Waterloo; Laboratorie Aim\'{e} Cotton, Campus d'Orsay URI: http://hdl.handle.net/1811/19441 Other Identifiers: 1999-TB-12