Category Physics

In a pump-probe experiment, the pump laser pulse first excites the 2D material, and later, at controllable time-delays, the probe laser pulse returns to the energy-pumped site to provide information about the evolution of the pump’s effect on the material. In the ORNL experiment, absorption of pumped energy first generated two excitons, X1 and X2. Dissociation of these excitons through hole trapping at the substrate freed their electrons. Then the arriving probe pulse generated new electron–hole pairs, which joined the remaining free electrons to form trions T1 and T2. Credit: Oak Ridge National Laboratory, U.S. Dept. of Energy

This all-sky movie shows a time lapse of a pulsating aurora on Jan. 3, 2012. Scientists compared the video, taken in Poker Flat, Alaska, over the course of three minutes, with satellite measurements of the numbers and energies of electrons raining down from the magnetosphere to better understand how electrons transfer energy to the upper atmosphere and create the auroras. The black mark traces the satellite foot point—the place where the satellite is magnetically connected to the aurora—of the Defense Meteorological Satellite Program satellite. Credits: NASA

Lightweight and high-power density capacitors are of particular interest for the development of hybrid and electric vehicles. The fast-charging devices allow for significant energy saving, because they can accumulate energy during braking and release it during acceleration. Credit: Xuan Yang and Kevin Yager

Collecting candle soot from the (a) tip of the flame and (b) middle of the flame. SS current collector (c) before and (d) after deposition of carbon soot.