  Some experimental evidences for methane are produced that the simple
transition from frequency scanning of nonlinear-optical resonances to magnetic
one may be accompanied with transition from sub-Doppler collisionally broadened
structure to sub-collision hyperfine one. It is conditioned by nonlinearity of
splitting of hyperfine sublevel for molecules in the adiabatically varied
magnetic field and respectively breaking the analogy of magnetic and frequency
scannings. The exact calculation of the resonance structure is considered for
molecules with only one spin subsystem. The approximately spin-additive
calculation of the structure is given for sufficiently fast rotating molecules
with greater number of spin subsystems. Within the same approximation an
example of hyperfine doubling in the magnetic and electric spectra of
nonlinear-optical resonance is considered for fluoromethane.
