离子晶体中的光诱导原子运动
Light-induced atomic motion in ionic crystals
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中文总结 AI 辅助
本研究提出离子晶体中原子位移的光激发新机制，以BaF₂为例实现光控缺陷演化，可提高STE信号产额，在电离辐射探测中具应用潜力。
中文摘要 AI 辅助
固体中的原子运动传统上由电离粒子与原子之间的弹性碰撞驱动，这种碰撞会传递动量并诱导晶格位移。本研究展示了一种基于闪烁离子晶体光激发的原子位移新机制。离子晶体因组成离子的闭壳层电子构型而成为独特体系，在这类材料中，带隙以上的激发会产生空穴，该空穴会强烈扭曲晶格，进而形成自陷空穴（STH）。自陷空穴通过库仑作用被电子吸引，从而形成自陷激子（STE）。本研究以最快的闪烁体之一氟化钡（BaF₂）为例，证明其STE结构可形成在室温下持续存在于晶格中的长寿命电子和空穴陷阱。这类被捕获的电子-空穴对占据弗伦克尔缺陷的氟空位-间隙氟对位置，只要形成自陷空穴（STH），就可通过光或电离辐射激发无差别地产生。此外，本研究还证明可通过光控制缺陷演化：对被捕获的电子或空穴进行选择性光刺激，可在后续时刻再生STE。这种光控缺陷工程可提高以光释光（OSL）形式出现的STE信号产额，并能对初始能量沉积的空间分布进行成像，在电离辐射探测领域具有巨大潜力。这些发现为萤石结构离子晶体中的闪烁和光释光提供了统一框架，可实现对类似体系中原子空位-间隙对的光学操控。
英文摘要
Atomic motion in solids is conventionally driven by elastic collisions between ionizing particles and atoms, which transfer momentum and induce lattice displacements. In this work, we demonstrate a different mechanism for atomic displacement based on optical excitation of scintillating ionic crystals. Ionic crystals are unique systems because of the closed-shell electronic configuration of their constituent ions. In these materials, excitation above the band gap generates a hole that strongly distorts the lattice, resulting in the formation of a self-trapped hole (STH). The STH is Coulomb-attracted to the electron, thereby forming a self-trapped exciton (STE). Here, we demonstrate that in BaF2 - one of the fastest scintillators - the STE structure promotes the formation of long-lived electron and hole traps that persist in the lattice at room temperature. Such trapped electron-hole pairs occupy vacancy-interstitial fluorine pair positions, and can be created indiscernibly using optical or ionizing radiation excitation, as long as the STH is formed. Further, we demonstrate that it is possible to control the defect evolution with light. Selective optical stimulation of the trapped electrons or holes enables the regeneration of the STE at later times. This light-controlled defect engineering allows us to increase the yield of the STE signal appearing as optically stimulated luminescence (OSL) and to image the spatial distribution of the initial energy deposition, holding strong potential for ionizing-radiation detection. These findings provide a common framework underlying scintillation and OSL in ionic crystals of the fluorite structure, allowing for optical manipulation of atomic vacancies-interstitial pairs in similar systems.
