  We study coherence effects in an atom having three metastable levels and
single life-time broadened upper state. Two laser fields couple ground states
to an excited one and an radio-frequency (rf) field operates between ground
state levels. We consider the case when the common level for the rf-field and
one of the laser field (to which we refer as the probing field) transitions is
twice degenerate. We predict a novel type of dark states (we call them non
Raman dark states), which in contrary to Raman resonances, do not require the
fulfillment of the two-photon resonance condition. We realize the configuration
in the atomic hydrogen and show that non Raman resonances are determined by the
geometry of the rf and probing field's polarizations. For ultra-cold atoms non
Raman resonances arise when the polarization vectors of the fields are parallel
or perpendicular to each other. For an atomic gas at room temperatures
electromagnetically induced transparency (EIT) resonances associated with Raman
and non Raman dark states are studied by taking into account spin-exchange
relaxation in the ground state of the hydrogen atom. We establish properties of
non Raman dark states by investigating the relation of EIT resonances to the
polarization geometry.
