A new route for the nonradiative decay of photoexcited, H-bonded, nitrogen-containing, heterocyclic dimers is Offered. and exemplified by a study of the pyrazole dimer. In some of these systems the N(3s) Rydberg state is the lowest excited singlet state This state is formed by direct light, absorption or by nonradiative transition from the allowed pi pi* state. An isomer of this Rydberg state is formed by H atom, transfer to the other, component of the dimer. The newly formed H-bonded radical pair is composed of two radicals (a H-adduct of pyrazole, a heterocyclic analogue of the NH4 radical) and the pyrazolium pi-radical. It is calculated to have a shallow local minimum And is the lowest point on the PES of the H-pyrazole/pyrazolium radical pair. This specie's can cross back to the ground state of the original dimer through a relatively small energy gap and compete with the H-atom loss channel, known for the monomer. In both Rydberg dimers, an electron occupies a Rydberg orbital centered mostly on one of the two components of the dimer. This Rydberg Center Shift (RCS) mechanism, proposed earlier (Zilberg, S.; Kahan; A.; Haas, Y. Phys. Chem. Chem. Phys. 2012, 14, 8836), leads to deactivation of the electronically excited dimer while keeping it intact. It, thus, may, explain the high photostability of the pyrazole dimer as well as other heterocyclic dimers.