二維電子光譜中訊號振盪之理論研究: 電子相干性或是振動相干性

Abstract

經過數十億年的演化,行光合作用的生物體(photosynthetic organism)已經 發展出精密的光捕獲系統 (light-harvesting system) 。這些系統可以有效率地捕捉光 能並將光能轉移到反應中心 (reaction centre)。近年來,科學家發展出二維電子光 譜(two-dimensional electronic spectroscopy)的技術,用以研究並瞭解光合作用系 統中的能量轉移的機制。在本論文中,吾人透過理論計算的方法去研究二維電子 光譜中量子拍(quantum beat)的現象,並檢驗如何辨別二維電子光譜中電子相干 性(electronic coherence)和振動相干性(vibrational coherence)。本研究工作發 現二維電子光譜可提供比過去認為更多的資訊並讓我們能更進一步瞭解光合作用 中能力轉移的機制。

Over billions of years, photosynthetic organisms have developed sophistic light-harvesting systems. These systems can efficiently capture solar energy and then transmit the energy to reaction centre with high quantum yield. We can learn about the mechanism of en- ergy transfer through two-dimensional (2D) electronic spectroscopy. So far, it is believed that the efficient energy transfer is related to quantum coherence. In this work, We study the coherence quantum beats in 2D electronic spectroscopy calculated by a theoretical method based on a time-nonlocal quantum master equation and a scheme for the evalua- tion of the third-order photon echo polarization. We aim to examine how electronic and vibrational coherence can be distinguished in 2D spectra. We do find unique characteris- tics of vibrational coherence that help us distinguish electronic and vibrational coherence. In this work we find that two-dimensional electronic spectroscopy provide more informa- tion and more understand the mechanism of energy transfer in photosynthetic organisms.