For all his sake possible, nature tends to repeat a certain event over and over again: the struggle between matter and light.
It drives the reaction in an infinite number of ways, but in the most common version, light triggers a reaction that starts when a photon hits an atom or molecule. In photosynthesis, photons from the sun strike the chlorophyll molecules in the plant to knock out electrons, causing the conversion of carbon dioxide and water into sugar and oxygen. When you get sunburned, the photons of ultraviolet light shoot and damage the DNA molecules in your skin. You’ll also find a technical solution, such as in solar panels, where silicon atoms embedded in a crystal convert photons from the sun into the flow of electrons that generate electricity.
But physicists still don’t know the details of what happens when photons collide with atoms and molecules. Play-by-play happens in attoseconds, which are quintillionths of a second (or 10).-18 of a second). It takes a special laser that burns attoseconds-long to study transient phenomena like this. You can think of the length of a laser pulse a bit like the shutter speed of a camera. The shorter the pulse, the faster you can picture the electron moving. By studying these times, physicists gain a better understanding of a fundamental process that is ubiquitous in nature.
Last month, physicists at several universities in China published their results Physical Review Letters showing that they measured the time it took for an electron to leave a two-atom molecule after being irradiated with a very bright and short laser pulse. Although the two-atom molecule is simple, their experimental method “opens up a new path” to study how light interacts with electrons in more complex molecules, the authors wrote in the paper. (He did not agree to an interview with WIRED.)
In this experiment, the researchers measured how long it took for the electrons to leave the molecule after the laser photons hit them. Specifically, they found that the electron bounces back and forth between the two atoms for 3,500 attoseconds before leaving. To put that into perspective, it’s a quadrillion times faster than the blink of an eye, which lasts one-third of a second.
To save time in this experiment, the researchers tracked the location of light, known as polarization, says physicist Alexandra Landsman of Ohio State University, who was not involved in the research. Polarization is a property of many types of waves, and it describes the direction in which they rotate. You can think about polarization by thinking about ocean waves. The way in which water waves start and build is their direction – it is the structure of the surface of the water and it is related to the direction of the wave.
Light waves are oscillations in the electromagnetic field, or energy that penetrates the atmosphere and pushes or pulls electricity. Light travels through space, orbiting this field, causing the field’s energy to go up and down in its motion, like waves in the ocean. The polarization of light describes the direction in which the particle rotates. When light in a certain direction hits an electron, it turns the electron back and forth in that direction.
