Rovibrational characterization of X Σ + 2 B 11 H + by the extrapolationof photoselected high Rydberg series in B 11 H

Optical-optical-optical triple-resonance spectroscopy of B 11 H isolates high Rydberg states that form series converging to rotational state specific ionization potentials in the vibrational levels of B 11 H + from ν + = 0 through 4. Limits defined by a comprehensive fit of these series to state-detailed thresholds yield rovibrational constants describing the X Σ + 2 state of B 11 H + . The data provide a first determination of the vibrational-rotational interaction parameter α e = 0.4821 cm − 1 and a more accurate estimate of ω e = 2526.58 cm − 1 together with the higher-order anharmonic terms ω e x e = 61.98 cm − 1 and ω e y e = − 1.989 cm − 1 . The deperturbation and global fit of series to state-detailed limits also yield a precise value of the adiabatic ionization potential of B 11 H of 79 120.3 ± 0.1 cm − 1 , or 9.810 33 ± 1 × 10 − 5 eV . High precision is afforded here by the use of graphical analysis techniques, narrow-bandwidth laser systems, and an analysis of newly observed, high principal quantum number Rydberg states that conform well with Hund's case (d) electron-core coupling limit.