报告人：Prof. Shaul Mukamel  Departments of Chemistry and Physics & Astronomy, University of California, Irvine, USA

主持人：Prof. Konstantin Dorfman

时  间：2021年9月24日（周五）上午10:00

地  点：腾讯会议 ID: 369 152 863

报告人简介：

Shaul Mukamel教授现任美国加州大学Irvine分校杰出教授，美国国家科学院院士。长期致力于非线性光学和光谱理论研究，为该领域先驱之一。他的理论研究工作受到实验科学家的广泛关注和推崇，常为世界各国的光源中心提供指导和建议。目前著有多部专著，其中《Principles of Nonlinear Optics and Spectroscopy》为光学、物理化学等领域经典教材。至今发表文章900余篇，论文被引数超过五万次，H因子108。荣获Ahmed Zewail ACS Award in Ultrafast Science and Technology 、The Optical Society (OSA) William F. Meggers Award 、Hamburg Prize for Theoretical Physics 等多个奖项。2013年和2015年分别当选美国艺术与科学院（American Academy of Arts and Sciences）院士和美国科学院（National Academy of Sciences）院士。

报告内容简介：

Conical intersections (CoIns) are ubiquitous features on the excited state landscapes of molecular systems. When wavepackets approach and pass a CoIn, a vibronic coherence emerges. The quantum behavior of this passage determines the outcome of virtually all photochemical and photophysical processes.  The efficiency of energy transport processes versus ultrafast internal conversion rates depends on the wavepacket branching at CoIns.

Recently developed ultrafast x-ray pulses and free electron lasers open up several techniques that probe electron and nuclear dynamics and coherence with unprecedented temporal, spectral and spatial resolutions. The TRUECARS technique uses a hybrid broadband/narrowband X-ray pulse pair to probe coherences via a stimulated Raman process. Fundamental properties like the transient energy distribution of the involved vibronic states are encoded in the signal and demonstrated for the RNA-nucleobase Uracil.  Quantum optimal control theory is employed to amplify the coherence magnitude - and thus the signal - by two orders of magnitude.

Time-resolved X-ray diffraction is simulated for azobenzene photoisomerization. Coherences contribute as a weak signature to the total signal through mixed elastic/inelastic photon scattering and provide a spatial image of the electron transition density around the CoIn. The stochastic nature of free electron lasers is used to generate covariance signals that enhance the resolution of nonlinear spectroscopy and diffraction signals.

[1] “Visualizing Conical Intersection Passages via Vibronic Coherence Maps Generated by Stimulated X-Ray Raman Signals”, Daniel Keefer, Thomas Schnappinger, Regina de Vivie-Riedle and Shaul Mukamel. PNAS, 117, 24069-24075 (2020)

[2] “Selective Enhancement of Spectroscopic Features by Quantum Optimal Control”, Daniel Keefer and Shaul Mukamel. PRL 126,163202 (2021)

[3] “Imaging Conical Intersection Dynamics During Azobenzene Photoisomerization by Ultrafast X-ray Diffraction”, Daniel Keefer, Flavia Aleotti, Jeremy Rouxel, Francesco Segatta, Bing Gu, Artur Nenov, Marco Garavelli, and Shaul Mukamel. PNAS January 19, 2021 118 (3) e2022037118

[4] “High temporal and spectral resolution of stimulated x-ray Raman signals with stochastic free-electron-laser pulses”, Stefano M. Cavaletto, Daniel Keefer, and Shaul Mukamel. Phys. Rev. X 11, 011029 (2021) DOI: 10.1103/PhysRevX.11.011029