  Nonlinear magneto-optical rotation is studied under non-equilibrium
conditions. The polarization rotation of linearly polarized light traversing a
rubidium vapor cell is observed versus the time-dependent (swept) longitudinal
magnetic field in the presence of static transverse magnetic fields. Presence
of the transverse fields modifies the character of the observed signals. In
particular, for weaker transverse fields, field sweep leads two-harmonic
oscillation of the polarization rotation while crossing zero. Unlike the
steady-state, it was found that two-frequency oscillations observed in the
transient signals, are independent of the transverse-field direction. For
stronger transverse fields, the oscillations deteriorate eventually reaching a
situation when no-oscillating dynamic signal, with distinct minimum close to
zero field, is observed. Experimental results are supported with theoretical
analysis based on the density-matrix formalism. The analysis confirms all the
features of experimental results while providing an provide intuitive
explanation of the observed behavior based on angular-momentum probability
surfaces used for density-matrix visualization.
