Electron kinetic effects in back-stimulated Raman scattering bursts driven by broadband laser pulses

We examine electron kinetic effects in broadband-laser-driven back-stimulated Raman scattering(BSRS)bursts using particle-in-cell simulations.These bursts occur during the nonlinear stage,causing reflectivity spikes and generating large numbers of hot electrons.Long-duration simulations are performed to observe burst events,and a simplified model is developed to eliminate the interference of the broadband laser’s random intensity fluctuations.Using the simplified model,we isolate and characterize the spectrum of electron plasma waves.The spectrum changes from a sideband structure to a turbulence-like structure during the burst.A significant asymmetry in the spectrum is observed.This asymmetry is amplified and transferred to electron phase space by high-intensity broadband laser pulses,leading to violent vortex-merging and generation of hot electrons.The proportion of hot electrons increases from 6.76%to 14.7%during a single violent burst event.We demonstrate that kinetic effects profoundly influence the BSRS evolution driven by broadband lasers.

Synergistic O^(2-)/Li^(+) Dual Ion Transportation at Atomic Scale

Te ion migration during electrochemical process is a fundamental scientifc issue for phase transition behavior and of technical importance for various functional devices,where cations or anions are active under electrical bias.Usually only one type of functional ion,O^(2-)or Li^(+),is activated due to their diferent migration energy barriers,cooperated by the valence change of other immobile ions in the host lattice matrix,e.g.,Co^(2+)/Co^(3+)and Mn^(3+)/Mn4+redox couples,owing to the charge neutralization.Here we select spinel Li4Ti5O12 as anode and construct an all-solid-state battery under a transmission electron microscope;a synergistic transportation of O^(2-)and Li^(+)driven by an electrical bias was directly observed at the atomic scale.A small amount of oxygen anions was extracted frstly as a result of its lowest vacancy formation energy under 2.2 V,leading to the vertical displacement of oxygen.Up to 2.7 V,an ordered phase with both Li-and O-defciency formed.Te Li^(+)and O^(2-)ions are simultaneously extracted out from the[LiO_(4)]tetrahedra due to the electroneutrality principle.Te migration paths of O and Li have been proposed and verifed by frst-principles calculations.Tese results reveal a brand new synergistic ion migration manner and may provide up-to-date insights on the transportation process of lithium ion conductors.