  We investigate the reversible diffusion-influenced reaction of an isolated
pair in two space dimensions in the context of the area reactivity model. We
compute the exact Green's function in the Laplace domain for the initially
unbound molecule. Furthermore, we calculate the exact expression for the
Green's function in the time domain by inverting the Laplace transform via the
Bromwich contour integral. The obtained results should be useful for comparing
the behavior of the area reactivity model with more conventional models based
on contact reactivity.
