Much attention has
been paid to the dynamics of both activated
gas-phase bimolecular reactions, which feature monotonically increasing
integral cross sections and Arrhenius kinetics, and their barrierless
capture counterparts, which manifest monotonically decreasing integral
cross sections and negative temperature dependence of the rate coefficients.
In this Perspective, we focus on the dynamics of gas-phase bimolecular
reactions with submerged barriers, which often involve radicals or
ions and are prevalent in combustion, atmospheric chemistry, astrochemistry,
and plasma chemistry. The temperature dependence of the rate coefficients
for such reactions is often non-Arrhenius and complex, and the corresponding
dynamics may also be quite different from those with significant barriers
or those completely dominated by capture. Recent experimental and
theoretical studies of such reactions, particularly at relatively
low temperatures or collision energies, have revealed interesting
dynamical behaviors, which are discussed here. The new knowledge enriches
our understanding of the dynamics of these unusual reactions.