General form of intramolecular nuclear spin isomers mixing in C3v-symmetry

For molecules with symmetry group C3v, a general form is considered of internal interaction causing transitions between nuclear spin isomers. Due to fundamental correlations between spin state of three equivalent protons and molecular rotation any mixing Hamiltonian must be a product of a spin-changing operator and an operator which provides transformation of rotation state. Appropriate operators are found. A special operator causes cycling transformations between states of three equivalent protons with different triple products of their spins: Operations in rotation space are made within the generalized Jordan-Schwinger approach to the theory of quantum angular momentum. The suggested model Hamiltonians encompass all possible mixing interactions causing conversion of nuclear spin isomers by the process of so-termed quantum relaxation.83