Symmetry-induced kinetic isotope effects in the dissociation dynamics of CHCl₃ ⁺ and CHCl₄ ⁻

Loss of Cl from CHCl₃ ⁺ with little excess energy is found to proceed via two distinct pathways, the reaction channel which is being followed is determined by a symmetry-induced kinetic isotope effect. Computational investigations suggest competition between a statistical adiabatic process and a process of electronic predissociation. For CHCl₄ ⁻ and CH₂Cl₃ ⁻, rotational predissociation contributes to the kinetic isotope effects for all isotopomers, whereas the particularly large effect observed for CH³⁵Cl₃ ³⁷Cl⁻ also originates from symmetry-induced degeneracy of vibrational modes in the C_3V point.