  We use transition path sampling to study evaporation in the SPC/E model of
liquid water. Based on thousands of evaporation trajectories, we characterize
the members of the transition state ensemble (TSE), which exhibit a
liquid-vapor interface with predominantly negative mean curvature at the site
of evaporation. We also find that after evaporation is complete, the
distributions of translational and angular momenta of the evaporated water are
Maxwellian with a temperature equal to that of the liquid. To characterize the
evaporation trajectories in their entirety, we find that it suffices to project
them onto just two coordinates: the distance of the evaporating molecule to the
instantaneous liquid-vapor interface, and the velocity of the water along the
average interface normal. In this projected space, we find that the TSE is
well-captured by a simple model of ballistic escape from a deep potential well,
with no additional barrier to evaporation beyond the cohesive strength of the
liquid. Equivalently, they are consistent with a near-unity probability for a
water molecule impinging upon a liquid droplet to condense. These results agree
with previous simulations and with some, but not all, recent experiments.
