The light changes the subject in ways that shape our world.Photon trigger changes in the proteins of the eye to allow the vision; sunlight splits water into hydrogen and oxygen and creates chemicals through photosynthesis, the light causes electrons to flow in semiconductors that form solar cells.In trying to enjoy this light-matter interaction, scientists and engineers are working to develop new technologies that rely on the manipulation of light instead of electrons.
The major difficulty is that, until now, it was impossible to directly measure how light manipulates matter at the atomic scale.More specifically, what happens when a photon hits an atom?The challenge has just been won by an international team of researchers, coordinated by Dr. Thornton Glover, who used the LCLS accelerator (Linac Coherent Light Source ) at Stanford University, USA.
Scientists have developed a technique that uses an X-ray pulse superbrilhante, combined with a light pulse of low frequency that our eyes can see, emitted by a laser.Addressing the two pulses combined for a diamond sample, the scientists were able to measure directly the first time, optical manipulation of the chemical bonds of the crystal, on the scale of individual atoms.
Unlike the technique of X-ray diffraction, commonly used in the study of proteins and other biological molecules, mixing waves and X-ray optics can detect how light resets the distribution of electric charge in a material.
“The conventional diffraction does not provide direct information on how the valence electrons respond to light, nor on the electric fields that arise on a material because of that response,” explained Dr. Glover. “But with the mixture of X-rays and wave optics, the modified energy X-ray tube to selectively load optically sensitive material.”
Besides the ability to directly measure, atomic-scale details of how light initiates changes such as chemical reactions or phase transitions, sensitivity to valence charge that the technique offers opens the possibility to follow the evolution of the chemical bonds or driving of electrons in a material.
Scientists have used the diamond to be a material with a structure and electronic properties well known, which allowed the assessment technique.
“The easiest kind of diffraction experiment is with crystals, and there is a lot to learn,” said Glover. “For example, light can be used to change the magnetic order in advanced materials, but often it is not clear exactly what the light does, on a microscopic scale, to initiate these changes.”
The expectation is that this new technique of mixing waves help to unravel these mechanisms and, once understood, allow to manipulate them.