MIT researchers discovered that light can cause evaporation of water from a surface without the need for heat. This “photomolecular effect” could be important for understanding climate change and for improving some industrial processes.
If you read the article, it’s pretty clear. Instead of the energy of the photons being used to heat the water molecules to state change, that energy is used to break the molecular bonds between small groups of water molecules, and those groups are small enough to then be picked up by the air and evaporate. This way, the energy contained in a photon is converting much more liquid water to water vapor than if that same amount of energy was actually used to excite the water molecules, as in a microwave.
It’s insane to think we’ve just discovered this now. Is it because we thought we understood evaporation completely and didn’t bother looking further into it ?
I’m not super sure. If I recall correctly, we’ve known for a while that something was going on, because surface hearing alone couldn’t account for all of the water evaporating from oceans, but we couldn’t tell what. In defense of humanity here, the concept of photons interacting with something as comparably massive as molecules is kinda wild. We were caught way off guard when the photoelectric effect was announced, and that’s photons interacting with whole atoms instead of just elementary particles. The idea of the photomolecular effect is thus even wilder.
I have a degree in chemistry from the 1980s. The school I went to was big into kinetics.
How is this any kind of new?
How is this different from how a microwave oven works?
If you read the article, it’s pretty clear. Instead of the energy of the photons being used to heat the water molecules to state change, that energy is used to break the molecular bonds between small groups of water molecules, and those groups are small enough to then be picked up by the air and evaporate. This way, the energy contained in a photon is converting much more liquid water to water vapor than if that same amount of energy was actually used to excite the water molecules, as in a microwave.
It’s insane to think we’ve just discovered this now. Is it because we thought we understood evaporation completely and didn’t bother looking further into it ?
I’m not super sure. If I recall correctly, we’ve known for a while that something was going on, because surface hearing alone couldn’t account for all of the water evaporating from oceans, but we couldn’t tell what. In defense of humanity here, the concept of photons interacting with something as comparably massive as molecules is kinda wild. We were caught way off guard when the photoelectric effect was announced, and that’s photons interacting with whole atoms instead of just elementary particles. The idea of the photomolecular effect is thus even wilder.
Microwaves aren’t resonant or anything fancy — they’re just dielectric heating.