  A general theoretical description of a magnetic resonance is presented. This
description is necessary for a detailed analysis of spin dynamics in
electric-dipole-moment experiments in storage rings. General formulas
describing a behavior of all components of the polarization vector at the
magnetic resonance are obtained for an arbitrary initial polarization. These
formulas are exact on condition that the nonresonance rotating field is
neglected. The spin dynamics is also calculated at frequencies far from
resonance with allowance for both rotating fields. A general quantum-mechanical
analysis of the spin evolution at the magnetic resonance is fulfilled and the
full agreement between the classical and quantum-mechanical approaches is
shown. Quasimagnetic resonances for particles and nuclei moving in
noncontinuous perturbing fields of accelerators and storage rings are
considered. Distinguishing features of quasimagnetic resonances in storage ring
electric-dipole-moment experiments are investigated in detail. The exact
formulas for the effect caused by the electric dipole moment are derived. The
difference between the resonance effects conditioned by the rf electric-field
flipper and the rf Wien filter is found and is calculated for the first time.
The existence of this difference is crucial for the establishment of a consent
between analytical derivations and computer simulations and for checking spin
tracking programs. Main systematical errors are considered.
