The sign reversal of the wave function under a $2\pi$ rotation ("spinor character") is demonstrated in a spin-1 system (deuterium) when only a two-level subsystem is irradiated. Under irradiation of all three levels of the system $2\pi$ symmetry is recovered, and a continuous variation from $4\pi$ to $2\pi$ symmetry is demonstrated by irradiation with two different, continuously adjustable asynchronous rf fields.

• Received 16 November 1977

DOI:https://doi.org/10.1103/PhysRevA.17.1561