Abstract

Rotational tunnel systems provide deep insight into the basic laws of quantum mechanics. For a review, see [1]. Let us take the -CH₃ entity as a prototype. A rotation by 2π/3 around the symmetry axis perpendicular to the plane of the protons leaves the relevant Hamiltonian invariant. The spatial wave functions have A- and E-type symmetries. Since such a rotation is equivalent with a double permutation of two protons, the total wave function (space ⊗ spin) has to be totally symmetric because of Pauli’s principle. That is, the Pauli principle puts a strong symmetry restriction onto the wave function of the -CH₃-rotor: In the E-type states, the total nuclear spin is 1/2, in the A-type states it is 3/2. As a consequence, a relaxation of the total spin in these kind of quantum rotors is always connected with a change of the rotational or librational wavefunction. The corresponding overall process is called spin conversion relaxation.

© 1992 Optical Society of America