Motional narrowing under Markovian and non-Markovian hopping transitions in inhomogeneous broadened absorption line shape
Motional narrowing under Markovian and non-Markovian hopping transitions in inhomogeneous broadened absorption line shape
复制标题
不均匀加宽吸收线形状中马尔可夫和非马尔可夫跳跃跃迁下的运动变窄
DOI：
10.1103/physreve.99.052115
复制
发表时间：
2019
影响因子：
2.4
通讯作者：
Marumoto Kazuhiro
中科院分区：
文献类型：
--
作者：
Seki Kazuhiko;Marumoto Kazuhiro
最近的实验显示最小的电子自旋或顺磁共振（ESR和EPR）的线宽作为逆温度的函数的启发，我们研究了运动变窄效应，通过考虑一个组合模型的载流子跃迁和静态分散的角频率引起的光谱中的不均匀加宽。角频率的色散是由局域场的分布引起的。在非均匀静态局域场下，两个位置之间的跃迁引起自旋的绝热弛豫。我们还考虑了自旋的原位固有（非绝热）弛豫。我们得到了自旋相关函数的精确解，明确考虑两个网站之间的马尔可夫和非马尔可夫过渡过程的过渡。吸收线形状用Voigt函数表示，Voigt函数是高斯函数和洛伦兹函数的卷积。利用Voigt函数的已知性质，我们讨论了半峰全宽的变化和线形的变化之间的相关性，这两者都是由运动窄化引起的。通过假设热激活过程的跳跃过渡和现场固有的松弛，我们表明，最小的宽度出现作为一个函数的反温度实验观察到的有机材料。与一般的看法相反，我们还表明，局部随机场下的高斯线形的狭窄并不一定导致洛伦兹线形，特别是在跳跃跃迁的等待时间分布中存在重尾性质的情况下。
Inspired by recent experiments showing a minimum of electron spin or paramagnetic resonance (ESR and EPR) line width as a function of inverse temperature, we studied the motional narrowing effect by considering a combined model of carrier transitions and static dispersion of the angular frequency giving rise to an inhomogeneous broadening in the spectrum. The dispersion of the angular frequency results from the distribution of the local field. The transition between the sites under inhomogeneous static local field induces adiabatic relaxation of the spin. We also considered the on-site inherent (nonadiabatic) relaxation of the spin. We obtained the exact solution of the spin correlation function by explicitly considering transitions between two sites for both Markovian and non-Markovian transition processes. The absorption line shape is expressed in terms of the Voigt function, which is a convolution of a Gaussian function and a Lorentzian function. Using the known properties of the Voigt function, we discuss the correlation between the change in the full-width at half-maximum and the change in line shape, both of which are induced by motional narrowing. By assuming thermal activation processes for both the hopping transition and the on-site inherent relaxation, we show that the minimum of the width appears as a function of inverse temperature as observed experimentally in organic materials. Contrary to the general belief, we also show that the narrowing of the Gaussian line shape under a local random field did not necessarily lead to a Lorentzian line shape in particular under the presence of heavy tail property in the waiting time distribution of hopping transitions.