NIST scientists have developed a new tabletop system that can capture ultrafast x-ray images of atoms and molecules with unprecedented time resolution, potentially revolutionizing the study of light-driven chemical reactions. The system, which uses a combination of visible light and x-ray beams, can capture images with 10 times better time resolution than large synchrotron facilities and collect x-rays with 100 to 1000 times better efficiency.
The new system, which is compact and can be operated in a conventional laboratory, has the potential to allow more routine study of actuation pathways and time scales in a wide range of materials. This could have significant practical impact for probing the quantum states of complex molecular systems and improving the efficiency of solar cells by finding materials that promote power conversion efficiency.
The system employs a highly unusual system for generating its visible-light and x-ray beams, which begins with the pulsed output from a near-infrared laser. The resulting 400 nm violet pump light is focused onto the sample to start the reaction of interest, while the second beam is focused on a water jet in a vacuum chamber to create a plasma that releases energy in the form of hard x-rays.
The tabletop device uses a completely different kind of detector, a superconducting transition edge sensor (TES), which NIST scientists have been improving for more than a decade. When a photon strikes the TES, it temporarily heats up the circuit enough to cause the resistance to rise and the current flow to drop; the magnitude of those effects is dependent on the energy of the incoming photon.
This reduction is particularly important when examining biological samples, such as reactions that play a key role in photosynthesis. “Photosynthesis has proven very difficult to study because x-ray analysis techniques damage the material even as they peer inside it,” says Miaja-Avila, who helped conduct the experiments and led the preparation of the journal article. “Our system could be very beneficial for studies of such damage-prone materials.”
“This measurement system breakthrough on a tabletop represents a major advance in x-ray material science instrumentation, combining the technological expertise of laser-generated x-ray production with high-resolution, high-efficiency x-ray collection,” says Bob Hickernell, a division chief of the NIST Physical Measurement Laboratory, where the research was performed. “It offers unique access for scientists and engineers to an important range of time-resolved x-ray measurements and practical applications in a small lab setting that otherwise requires scarce and expensive x-ray beam time in a large-scale facility.”
Source: https://www.nist.gov/news-events/news/2016/11/seeing-lights-effect-atoms-within-picoseconds
Keywords: X-rays, Photoreaction, Ultrafast, Spectroscopy, Photon
