화학공학소재연구정보센터
Journal of Physical Chemistry A, Vol.113, No.47, 13237-13245, 2009
Spectroscopic Observation and Characterization of H+H- Heavy Rydberg States
A series of discrete resonances was observed in the spectrum of H,, which can be unambiguously assigned to bound quantum states in the I/R Coulombic potential of the H+H- ion-pair system. Two-step laser excitation was performed, using tunable extreme ultraviolet radiation at lambda = 94-96 nm in the first step, and tunable ultraviolet radiation in the range lambda = 310-350 nm in the second step. The resonances, detected via H+ and H-2(+) ions produced in the decay process, follow a sequence of principal quantum numbers (n = 140-230) associated with a Rydberg formula in which the Rydberg constant is mass scaled. The series converges upon the ionic H+H- dissociation threshold. This limit can be calculated without further assumptions from known ionization and dissociation energies in the hydrogen system and the electronegativity of the hydrogen atom. A possible excitation mechanism is discussed in terms of a complex resonance. Detailed measurements are performed to unravel and quantify the decay of the heavy Rydberg states into molecular H-2(+) ions, as well as into atomic fragments, both H(n = 2) and H(n = 3). Lifetimes are found to scale as n(3).