Scientists Blasted Water With Light 10 Billion Times Brighter Than Sunlight. It Still Didn't Evaporate Faster.

Key Points:

• A new study published in PNAS challenges previous claims of a "photomolecular effect," suggesting visible light does not enhance water evaporation through nonthermal means at the air-water interface.
• Researchers from the Max Planck Institute used direct macroscopic and microscopic measurements under various light wavelengths and intensities, finding no measurable changes in evaporation rates or hydrogen bonding in water molecules.
• Even extreme light intensities, exceeding solar flux by over ten orders of magnitude, failed to produce the purported photomolecular effect, indicating hydrogen bonds at the water surface remain stable under visible and near-infrared light.
• The study suggests prior observations of light-enhanced evaporation may have resulted from indirect effects like heat transport, light scattering, or physical forces in complex materials rather than an intrinsic photophysical property of water.
• These findings provide a benchmark for understanding light-water interactions and imply that visible-light-driven evaporation enhancements likely arise from photothermal or geometric factors in absorbing materials, not a new evaporation mechanism.