该研究团队利用FERMI自由电子激光器（FEL）的极紫外相干脉冲，对高定向热解石墨进行了汤姆逊散射研究。研究人员观察到了明显的非线性行为，并详细描述了激发FEL光束和散射辐射的相干性质。他们发现，随着光强的增加，汤姆逊散射截面出现增强，这与迪克超辐射现象类似，因此被解释为超辐射汤姆逊散射的观测。此外，该过程还触发了相干的低q (<0.3 A-1)低能量声子的产生。
实验数据和分析提供了有关样品特性、吸收、散射因子、相干声子能量和布居数的定量信息，为深入研究复杂材料的深层性质开辟了新的道路。
附：英文原文
Title: Superradiant Thomson scattering from graphite in the extreme ultraviolet
Author: Fasolato, Claudia, Stellino, Elena, Principi, Emiliano, Mincigrucci, Riccardo, Pelli-Cresi, Jacopo Stefano, Foglia, Laura, Postorino, Paolo, Sacchetti, Francesco, Petrillo, Caterina
Issue&Volume: 2024-1-19
Abstract: We study the Thomson scattering from highly oriented pyrolitic graphite excited by the extreme ultraviolet, coherent pulses of FERMI free electron laser (FEL). An apparent nonlinear behavior is observed and fully described in terms of the coherent nature of both exciting FEL beam and scattered radiation, producing an intensity-dependent enhancement of the Thomson scattering cross-section. The process resembles Dicke’s superradiant phenomenon and is thus interpreted as the observation of superradiant Thomson scattering. The process also triggers the creation of coherent, low-q ( <0.3 A-1), low energy phonons. The experimental data and analysis provide quantitative information on the sample characteristics, absorption, scattering factor, and coherent phonon energies and populations and open the route for the investigation of the deep nature of complex materials.
DOI: 10.1073/pnas.2221293121
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2221293121