  In molecular photochemistry, the non-equilibrium character and subsequent
ultrafast relaxation dynamics of photoexcitations near the Franck-Condon region
limit the control of their chemical reactivity. We address how to harness
strong light-matter coupling in optical microcavities to isolate and
preferentially select specific reaction pathways out of the myriad of
possibilities present in large-scale complex systems. Using Fermi's Golden Rule
and realistic molecular parameters, we estimate the extent to which molecular
configurations can be "locked" into non-equilibrium excited state
configurations for timescales well beyond their natural relaxation times. For
upper polaritons--which are largely excitonic in character, molecular systems
can be locked into their ground state geometries for tens to thousands of
picoseconds and varies with the strength of the exciton/phonon coupling
(Huang-Rhys parameter). On the other hand, relaxed LP lifetimes are nearly
uniformly distributed between 2.1-2.4\,ps and are nearly independent of the
Huang-Rhys parameter.
