  We analyze theoretically the entanglement between two non-planar and light
identical molecules (e.g., pyramidal as $NH_3$) that present inversion doubling
due to the internal spatial inversion of their nuclear conformations by
tunneling. The peculiarity of this system lies in the simplicity of this type
of molecular system in which two near levels can be connected by allowed
electric dipole transition with considerable value of the dipole moment
transition and negligible spontaneous emission because the transition is in the
microwave or far-infrared range. These properties give place to entanglement
states oscillating by free evolution with frequency determined by the
dipole-dipole interaction and negligible spontaneous decay, which allows to
consider an efficient quantum Zeno effect by frequent measurements of one of
the entangled states. If the molecules are initially both in the upper (or
lower) eigenstate, the system evolves under an external radiation field, which
can induce oscillations of the generated entangled states, with frequency of
the order of the Rabi frequency of the field. For a certain detuning, a
symmetric entangled state, eigenstate of the collective system can be
populated, and given its negligible spontaneous emission, could be maintained
for a time only limited by external decoherence processes which could be
minimized. Although the data used are those of the $NH_3$ molecule, other
molecules could present the same advantageous features.
