1. Regions of potential-energy surfaces where there are valleys are sometimes referred to as arrangement channels. The reactant channel or entrance channel is that corresponding to configurations similar to those of the reactants; the product channel or exit channel relates to configurations similar to those of the products. In collision theory, the specification of a complete set of quantum numbers in a given arrangement channel is called a channel.
    PAC, 1996, 68, 149 (A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)) on page 157
  2. (in analysis) That part of an analytical instrument that is dedicated to a single analytical procedure, including the transducer. This term relates to the internal operation of certain types of instruments, particularly in clinical chemistry. The general term channel has a much broader meaning, and the term is not recommended.
    PAC, 1989, 61, 1657 (Nomenclature for automated and mechanised analysis (Recommendations 1989)) on page 1661