When in a condensed phase, or in a dense gas, reactant
molecules come together, or species are formed in proximity to one another, and are caged in by surrounding molecules, they may undergo a set of collisions known as an encounter
; the term 'cage effect
' is then applied.
effect is also known as the Franck–Rabinowitch effect.
PAC, 1996, 68, 149
(A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996))
on page 155