Collision-induced rovibrational energy transfer in small polyatomic molecules: the role of intramolecular perturbations

Brian J. Orr*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


Various forms of time-resolved optical double-resonance spectroscopy facilitate rotationally resolved measurements of collision-induced intramolecular vibration-to-vibration (V–V) energy-transfer processes, which take a gas-phase polyatomic molecule from one distinct rovibrational energy level to another. Of longstanding mechanistic interest are questions concerning the extent to which such V–V energy transfer (ET) may be influenced by intramolecular perturbations – notably Fermi resonance (and other anharmonic mixing effects) and Coriolis coupling – within polyatomic molecular rovibrational manifolds of interest. It is evident that quantum-mechanical interference effects can arise, either inhibiting or enhancing the probability of collision-induced ET in perturbed rovibrational manifolds of certain small gas-phase polyatomic molecules, notably CO2, D2CO and C2H2. This article focuses on a blend of high-resolution rovibrational spectroscopy (characterising initial and final molecular levels and their intramolecular perturbations) and collision dynamics (with colliding molecules defined in terms of isolated-molecule spectroscopic basis states). It aims to offer fresh insights and to consider some apparent mechanistic anomalies (e.g. collision-induced quasi-continuous background effects in the 4νCH rovibrational manifold of C2H2). Various reported experiments and related theoretical treatments are critically re-examined, in order to pose and address mechanistic questions some of which still challenge detailed understanding.

Original languageEnglish
Pages (from-to)3666-3700
Number of pages35
JournalMolecular Physics
Issue number23-24
Early online date4 Jul 2018
Publication statusPublished - 2018
EventThe 25th Colloquium on High-Resolution Molecular Spectroscopy - Helsinki, Helsinki, Finland
Duration: 20 Aug 201725 Aug 2017


  • energy transfer
  • intramolecular perturbations
  • molecular collisions
  • Rovibrational spectroscopy


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