报告题目: Prof. Dr. Vitali Averbukh 系列报告

报告摘要:

Two-Dimensional Partial Covariance Mass Spectrometry for Macromolecular Sequence Analysis

2024年10月9日 (星期三) 18:00

Two developed -dimensional as a tool covariance for the study mapping of mechanisms spectroscopy of radiation was originally -induced fragmentation of di- and tri-atomic molecules. The main problem arising in applications of covariance mapping to larger molecular species stems from the overwhelming spurious signals of no physical significance induced by fluctuations of experimental parameters. We have recently pioneered the self-correcting partial-covariance spectroscopy which eliminates the need for continuous monitoring of multiple fluctuating experimental parameters enabling covariance mapping of macromolecular decompositions. This opens the opportunity for mechanistic studies of macromolecular decompositions using covariance mapping. Moreover, we demonstrate that the two-dimensional partial covariance mass spectrometry (2D-PC-MS) based on the self-correcting partial covariance mapping has an unparalleled analytical capability. It enables confident reconstruction of the biomolecular sequences in the cases where the standard MS fails as a matter of principle – even at the theoretical infinite mass precision and resolution, as well as full sequence coverage by fragmentations. The sequence reconstruction can be automated both for peptides and for intact proteins.

Quantum Coherence and Entanglement in Attosecond Photoionization

2024年10月16日 (星期三) 18:00

In hole thismigration presentation, experiments I will discuss performed the theoretical at the LCLS interpretation and FLASHof Xthe -rayrecent free electron laser facilities and targeting the electronic observables, such as timedependent Auger electron signal. I will also describe our progress in developing the ab initio many-electron theoretical tools, such as B-spline ADC, that allow us to gain insight into the mechanisms of the onset and decay of the coherent hole dynamics. Combining application of such ab initio tools with analytical modelling has led us to propose a number of new spectroscopic approaches for direct observation of coherent many-electron dynamics in ionized systems. A central role in the generation of the ionic coherence belongs to the quantum entanglement between the photoelectron and the atomic or molecular ion. We have developed and simulated numerically a Bell test for probing the quantum entanglement in photoionization. We have designed and simulated the quantum protocol for entanglement quantification for the case of noble gas atoms photoionized by ultrashort, circularly polarized infrared laser pulses in the strong-field regime, demonstrating robust violation of the Bell inequality. The Bell test developed in our work detects entanglement between the internal states of the Ar+ and the spin states of the photoelectron by exploiting the spin polarization of the photoelectron beam.

Many-Electron Theory of Inter-Atomic Decay Processes in Clusters

2024年10月23日 (星期三) 18:00

Inter-atomic decay processes are a new class of electronic decay phenomena in clusters, where ionization of one of the cluster units leads to non-radiative decay of the formed vacancy by electron emission from another cluster unit. The first physical phenomenon of this kind, inter-atomic (or inter-molecular) Coulombic decay (ICD) was predicted by Cederbaum and co-workers in 1997 and observed experimentally several years later. Both theoretical and experimental investigations have established ICD as a highly general and a very general decay process. Indeed, ICD is characteristic of vacancy states of van der Waals clusters, hydrogen bonded clusters, and even endohedral fullerenes. The ICD lifetimes were found to belong to the range of 1–100 fs, many orders of magnitude shorter than those of the competing photon emission process. Thus, ICD is the main decay mode of moderate-energy (Auger-inactive) inner shell vacancies in clusters. The mechanism of ICD, rests on the energy transfer between the cluster units at large interatomic distances, amplified by electron cloud overlap at shorter distances. Further inter-atomic decay processes include both energy-transfer-based and electron-transfer-based phenomena. In this talk, I will review the existing variety of inter-atomic decay mechanisms, their theoretical description by means of many-electron theory and outline the perspectives for further development of this field of research.

报告人简介： Prof. Dr. Vitali Averbukh is a theoretician working on a wide range of topics in molecular spectroscopy, from ab initio many-body theory of attosecond electron dynamics to biomolecular mass spectrometry. In the field of attosecond physics, he studies fundamental ultrafast electronic processes that occur in molecules and clusters following excitation and/or ionisation. These electronic transitions are driven by electron-electron interaction and are the basic manifestation of the electron correlation in nature. His group is developing and using first principles many-electron theoretical methods to investigate the complex dynamics of the known electronic rearrangements and to predict new physical phenomena of this type. The ab initio computational method developed in his group recently, B-spline algebraic diagrammatic construction (ADC), allows us to look inside the radiative and non-radiative many-electron transitions in order to study the onset and the effect of quantum coherence on these phenomena.

主持联系人：李铮(Email: zheng.li@pku.edu.cn)

科学前沿报告会(635)