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"Observations of the high vibrational levels of the B '(B)over-bar(1)Sigma(+)(u) state of H-2"

Journal of Chemical Physics, Vol. 144, Issue 1, American Institute of Physics, January 2016. Written with A.M. Chartrand, W. Duan, and R.C. Ekey.

Double-resonance laser spectroscopy via the EF (1)Sigma(+)(g), v' = 6, J' = 0-2 state was used to probe the high vibrational levels of the B"(B) over bar (1)Sigma(+)(u) state of molecular hydrogen. Resonantly enhanced multiphoton ionization spectra were recorded by detecting ion production as a function of energy using a time of flight mass spectrometer. New measurements of energies for the v = 51-66 levels for the B"(B) over bar state of H-2 are reported, which, taken with previous results, span the v = 46-69 vibrational levels. Results for energy levels are compared to theoretical close-coupled calculations [L. Wolniewicz, T. Orlikowski, and G. Staszewska, J. Mol. Spectrosc. 238, 118-126 (2006)]. The average difference between the 84 measured energies and calculated energies is -3.8 cm(-1) with a standard deviation of 5.3 cm(-1). This level of agreement showcases the success of the theoretical calculations in accounting for the strong rovibronic mixing of the (1)Sigma(+)(u) and (1)Pi(+)(u) states. Due to the ion-pair character of the outer well, the observed energies of the vibrational levels below the third dissociation limit smoothly connect with previously observed energies of ion-pair states above this limit. The results provide an opportunity for testing a heavy Rydberg multi-channel quantum defect analysis of the high vibrational states below the third dissociation limit.