Quantum yield: The term and the symbol. A historical search

Abstract

Einstein's Photochemical Equivalence Law, i.e. one quantum of light absorbed per molecule, played a very important role in the development of photochemistry in the early part of the 20th century. The corresponding terminology, quantum yield and its symbol Φ, became accepted usage in a haphazard manner, which is presented in this paper. © 2010 The Royal Society of Chemistry and Owner Societies.