Classical and quantum dynamics of long lived doubly excited vibrational states of triatomic molecules

Abstract

Local mode A–B–A triatomic molecules are modeled as coupled Morse oscillators using classical and quantum techniques. Classical studies indicate large volumes of nondissociating classical phase space, even well above the dissociation threshold. The trapped classical motion corresponds to excitation in both bond modes of the system. Quantum studies have been performed as a function of coupling constant (mass ratio) and of dissociation energy. Quantum doubly excited vibrational resonances are found with lifetimes of up to 10⁶ vibrational periods. The lifetimes of the states, as ℏ (or dissociation energy) is varied, are in accordance with the correspondence principle. Substantial deviation from the predictions of statistical theories is noted in the distributions of lifetimes, as well as in the fact that all of the resonances are only weakly coupled to the ‘‘direct’’ dissociation channels.