Selvakumar Sellaiyan, Sivaji Krishnan, Arulchakkaravarthi Arjunan, Sankar Sambasivam
Materials Science Center, Department of Nuclear Physics, University of Madras, Guindy Campus, Chennai 600 025, India.
Phys Chem Chem Phys. 2014 Aug 14;16(30):15934-40. doi: 10.1039/c4cp01386g.
We present the mapping of electron momentum distribution (EMD) in a single crystal of anthracene by two-dimensional angular correlation of positron annihilation radiation (2D-ACAR). The projected EMD is explained on the basis of the crystallographic features of the material. The EMD spectra provide information about the positron states and their behavior and also about the hindrance of the positronium (Ps) formation in this material. The EMD has exhibited evidence for the absence of free volume defects. The characteristic EMD features regarding the delocalized electronic states are explained. Further, scintillation characteristics such as fluorescence and time-correlated single photon counting have also been studied. The emission peaks are attributed to vibrational bands of fluorescence emission from the singlet excitons and lifetime components are observed to be due to singlet fission and the singlet-singlet excitons annihilation.
我们通过正电子湮没辐射的二维角关联（2D - ACAR）展示了蒽单晶中电子动量分布（EMD）的映射。基于材料的晶体学特征对投影EMD进行了解释。EMD光谱提供了有关正电子态及其行为的信息，以及有关该材料中 positronium（Ps）形成的阻碍的信息。EMD已显示出不存在自由体积缺陷的证据。解释了与离域电子态相关的特征EMD特征。此外，还研究了诸如荧光和时间相关单光子计数等闪烁特性。发射峰归因于单重态激子荧光发射的振动带，并且观察到寿命成分是由于单重态裂变和单重态 - 单重态激子湮没。
