Spectroscopy of the high Rydberg states of boron monohydride
Abstract
Optical-optical-optical triple resonance spectroscopy is applied to resolve systems of high Rydberg states in BH. Rydberg series are isolated using third photon optical transitions originating from the photoselected B1Σ + (v", N" = 0) state. Final states are observed converging to X2Σ+ BH+ limits with N+ = 0, 1, and 2, and v+ = v" and v" + 1. The Rydberg systems quantitatively characterize a fundamental example of electron-orbital-cation core rotational coupling. The coupling of orbital and rotational angular momenta in observed np Rydberg series systematically perturbs level energies and distributes lifetime in a well-isolated two-channel rotronic interaction that spans hundreds of wave numbers. The set of measured rovibrational ion limits facilitates calculation of new more extensive vibrationally dependant spectroscopic constants characterizing the X2Σ+ state of BH +. Resonance lineshapes reveal clear patterns of slowly changing discrete-continuum autoionization dynamics below and above thresholds. The displayed peak shapes reveal the influence of excitation schemes and state-to-state coupling strengths on autoionization dynamics, and are characteristic of two and three channel models. Rydberg series converging to v+ = 0 couple strongly to decay channels for electron loss and boron-hydrogen bond cleavage to neutral atoms. Strong isolated-core excitations of the high v = 0 Rydberg states and dissociative recombination above the v+ = 0 threshold are also observed in this spectrum.
Degree
Ph.D.
Advisors
Grant, Purdue University.
Subject Area
Chemistry|Molecules
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