A quantum approach to paramagnetic resonance

In the semi-classical theory of the problem of interaction of radio-frequency (r.f.) field with electron or nuclear spin, the application of quantization is restricted to the spin system only, the r.f. field being treated classically. In this paper, a purely quantum approach is discussed for a system with spin > 1/2 using a Glauber vector to describe coherent excitations of the r.f. field. It is illustrated here for the case of spin 3/2. One finds that this quantum approach contains the classical one. (author)