  The evaporation of water is ubiquitous in nature and industrial technologies.
The known mechanism for evaporation is "thermal evaporation" which highlights
the energy input for evaporation is via heat. Due to the weak absorption of
water to visible light, the first step to using solar energy to evaporate water
is usually by converting it into thermal energy through photothermal processes
via additional absorbing materials. Contrary to this conventional wisdom, we
report here strong absorption of photons in the visible spectrum at the
water-vapor interface by direct cleavage of water clusters via a process we
call photomolecular effect. We show that this process happens at the
water-vapor interface by measuring the dependence of the photomolecular
evaporation rate on the wavelength, the angle of incidence, and the
polarization of the incident light. The spectra signatures in the vapor phase
further support the photomolecular effect. Despite the long propagation lengths
of visible light in bulk water, we demonstrate that they can heat a thin layer
of fog easily, suggesting that this process is ubiquitous. The photomolecular
effect will have significant implications for the earth's water cycle, global
warming, plant transpiration, as well as different technologies involving the
evaporation of liquids from drying to power generation
