【摘要】 近年的发展日益证明,固体中的局域电子态所导致的晶格弛豫(晶格原子位置移动)是局域电子态的一项基本特征,能够引起许多重要的效应。在局域态的吸收和发射光谱中,由于晶格弛豫而引起斯托克斯位移和光谱的多声子结构(多声子的光跃迁)。晶格弛豫又可以在不同电子态之间引起无辐射跃迁,其中的能量变化完全由多声子的发射或吸收来补偿(多声子无辐射跃迁)。本文以线性的电子—声子作用和简谐近似的晶格模型为基础,系统地总结阐明多声子的光跃迁理论和多声子的无辐射跃迁理论。关于光跃迁的部份既介绍了直接计算跃迁几率的方法,也介绍了采用傅里叶变换的理论,并分析了连续谱和多声子结构相互叠加的一个光谱实例。关于无辐射跃迁的部份着重分析和澄清了多年来环绕所谓“康登近似”出现的矛盾,从而把近年来不同的理论发展置于统一的基础之上。介绍了估算跃迁几率的最陡下降法。最后讨论了强耦合和弱耦合的情形。更多还原

【Abstract】 Recent solid state investigations increasingly emphasize that lattice relaxation represents a basic feature of localized electronic states and is responsible for many important effects. It is well known that lattice relaxation casues peak shifts and gives rise to various multiphonon structures in the absorption and emission spectra of localized centres. More recent researches point to the importance of non-radiative transitions caused by lattice relaxation,whereby the energy balance is maintained by the emission or absorption of phonons(multiphonon non-radiative transitions).The present article gives a systematic presentation of the theories of multiphonon radiative and non-radiative transitions,on the basis of a linear electron-phonon interaction and a harmonic lattice model. In the part on radiative transitions,both the direct calculation of the transition probability and the more powerful method making use of Fourier transforms are elucidated.A spectrum with multiphonon peaks superposed on a continuous band is analyzed as an example. The part on non-radiative transition begins with a critical analysis of the so-called "Condon approximation",which leads to a unified presentation of the results of the theoretical developments in recent years. The approximate method(stee-pest descent method)for calculating the transition probability is described and the important extreme cases of strong coupling and weak coupling are discussed.更多还原