Abstract The study of carbon clusters led to the discoveries of fullerenes, carbon nanotubes, and graphene. Are there other elements that can form similar nanostructures? To answer this question, the speaker and his research group have focused on boron clusters, which have been investigated using photoelectron spectroscopy in combination with computational chemistry. They have found that bare boron clusters possess planar structures, in contrast to that of bulk boron, which is dominated by three-dimensional polyhedral building blocks. The discovery of planar boron clusters laid the foundation for 2D boron nanomaterials. In particular, the observation of the planar B36 cluster with a central hexagonal vacancy provided the first experimental evidence that single-atom boron-sheets with hexagonal vacancies (borophenes) were viable. Borophenes have since been synthesized and characterized on inert substrates, forming a new class of synthetic 2D materials. The B40 cluster was found to be an all-boron fullerene, whereas the largest boron cluster (B48–) characterized to date possesses a bilayer structure, suggesting the feasibility of bilayer borophenes. Boron forms important bulk boride materials with most metals in the periodic table. Many transition-metal borides are superhard materials, while lanthanide borides are essential magnetic materials. Metal boride clusters are ideal systems to probe the metal-boron bonding in boride materials. They have observed a quadruple bond between Rh and B (Rh≣B), as well as a lanthanide-boron cage cluster. The study of larger transition-metal boride clusters suggested the possibility of metallo-borophenes. The speaker will also discuss recent advances in their investigation of large boron clusters. About the Speaker Prof. WANG Lai-Sheng obtained his BS in Chemistry from Wuhan University in 1982 and his PhD in Chemical Physics from the University of California, Berkeley in 1990. He did postdoctoral work at Rice University before he took a joint position in 1993 between the Department of Physics at Washington State University and Pacific Northwest National Laboratory. In 2009, he joined Brown University and is currently the Jesse H. and Louisa D. Sharpe Metcalf Professor of Chemistry. Since July 2019, he has been serving as the Chair of the Department of Chemistry at Brown University. Prof. Wang’s research involves experimental studies of size-selected nanoclusters using photoelectron spectroscopy and imaging. Research in his lab has led to the discoveries of golden cages and golden pyramids, planar and aromatic boron clusters, borophenes, and borospherenes. His group has also pioneered the application of electrospray ionization for spectroscopic studies of solution anions in the gas phase, in particular, multiply-charged anions and microsolvated anions. His lab has developed cryogenically-cooled 3D quadrupole ion-trap techniques to create cold anions from electrospray ionization for spectroscopic investigations using photoelectron spectroscopy and high-resolution photoelectron imaging. Current research projects in Prof. Wang’s lab include the investigation of the structures and bonding of size-selected boron and boride clusters, probing noncovalent excited states of cold anions using photodetachment and photoelectron spectroscopy, the investigations of astronomically relevant anions and molecules, as well as the syntheses of ligand-protected gold nanoclusters with in situ catalytic active sites. He has served on the editorial board of Journal of Physical Chemistry, Chinese Journal of Chemical Physics and Chemical Physics Letters. Prof. Wang is the recipient of the 2023 Herbert P. Broida Prize and the 2021 E. Bright Wilson Award in Spectroscopy, both from the American Chemical Society. He also received the 2016 Creativity Award from the US National Science Foundation and the 2014 Earle K. Plyler Prize for Molecular Spectroscopy & Dynamics from the American Physical Society. He was elected as a Fellow of the American Association for the Advancement of Science in 2007, the John Simon Guggenheim Memorial Foundation in 2005, and the American Physical Society in 2003. For Attendees' Attention Seating is on a first come, first served basis.    

Abstract Precision spectroscopy of the hydrogen atom, a fundamental two-body system, has been instrumental in shaping quantum mechanics. Today, advances in theory and experiment allow us to extend such high-precision studies to more complex many-body systems. In this talk, the speaker will present his team's recent laser spectroscopy work on a select class of computable systems — including atomic helium (three-body), molecular hydrogen (four-body), and multi-electron species like CO — where state-of-the-art ab initio calculations achieve spectroscopic accuracy. By comparing experimental and theoretical transition frequencies at the 12-digit level, the team is able to test quantum mechanics and reveal novel quantum phenomena. Beyond frequencies, the team's ppm-level measurements of spectral intensities open applications in primary thermometry, isotopic analysis, and gas metrology. However, persistent interlaboratory discrepancies highlight remaining challenges, motivating further refinement of both experimental and theoretical approaches. About the Speaker Prof. HU Shui-Ming received his BS (1995) and PhD (2000) in Chemical Physics from the University of Science and Technology of China (USTC), followed by postdoctoral research at Rice University and Argonne National Laboratory. Awarded the prestigious National Science Fund for Distinguished Young Scholars in 2012, he currently serves as Professor of Chemical Physics at USTC, the Director of the Division of Advanced Measurement Instruments at the Hefei National Research Center for Physical Sciences at the Microscale, and Council Member of the Chinese Society for Measurement. His research focuses on developing novel laser spectroscopy techniques with ultrahigh precision and sensitivity, with applications spanning fundamental studies of atomic and molecular physics, chemical kinetics, optical metrology, trace gas analysis, and the development of advanced spectroscopic instrumentation for both scientific and industrial applications.  For Attendees' Attention Seating is on a first come, first served basis.

Abstract Surfaces and interfaces are ubiquitous in Nature. Sum-frequency generation vibrational spectroscopy (SFG-VS) is a powerful surface/interface selective and sub-monolayer sensitive spectroscopic technique to interrogate the vibrational spectroscopy, structure, and conformation, as well as optical activity, and vibrational dynamics of molecular surfaces and interfaces. The difficulties that have limited the application of SFG-VS to broad scientific problems regarding complex surfaces and interfaces, such as the difficulties in spectral assignment, accurate measurement and experimental as well as computational analysis of the SFG spectrum, have been mostly overcome with the recent developments. This presentation discusses the most recent developments in SFG-VS, particularly on the further development of the quality and sensitivity of the sub-wavenumber high resolution broadband SFG-VS (HR-BB-SFG-VS), and the future perspectives of the applications of SFG-VS as well as other nonlinear vibrational spectroscopy to surface/interface studies and beyond.1,2 References: [1] Wang, H. F.; Velarde, L.; Gan, W.; Fu, L., Quantitative sum-frequency generation vibrational spectroscopy of molecular surfaces and interfaces: Lineshape, polarization, and orientation. 2015, Annu. Rev. Phys. Chem., 66, 189-216. [2] Wang, H.-F., Sum frequency generation vibrational spectroscopy (SFG-VS) for complex molecular surfaces and interfaces: Spectral lineshape measurement and analysis plus some controversial issues. 2016, Prog. Surf. Sci., 91, 155-182. About the Speaker Prof. WANG Hongfei received his BS in Chemical Physics from the University of Science and Technology of China (USTC) in 1988 and continued his graduate studies in laser chemistry at USTC until 1991. He then obtained his PhD in Physical Chemistry from Columbia University in 1996. After two and a half years of postdoctoral work at the University of Pennsylvania, in collaboration with the DuPont Marshall Laboratory in Philadelphia, he joined the Molecular Reaction Dynamics Laboratory at the Institute of Chemistry, Chinese Academy of Sciences (ICCAS) as a Professor. At ICCAS, he served as the Director of the Molecular Reaction Dynamics Laboratory from 2000 to 2004 and as the Deputy Director of the State Key Laboratory of Molecular Reaction Dynamics during the same period. In 2009, he moved to the US and joined the Environmental Molecular Sciences Laboratory at the Pacific Northwest National Laboratory of the Department of Energy as a Chief Scientist. He returned to China in 2017 and joined Fudan University as a Professor of Chemistry. He later moved to the School of Science at Westlake University, where he is currently a Full Professor of Chemistry. Prof. Wang's research interests include the structure and reaction dynamics of surface and interface, linear and nonlinear optical spectroscopy and modern analytical spectroscopy. He is mostly known for his "seminal contributions to the development of surface nonlinear vibrational spectroscopy and to the understanding of molecular interaction and structure at interfaces". His most cited paper so far is a systematic survey on the "Quantitative Spectral and Orientational Analysis in Surface Sum Frequency Generation Vibrational Spectroscopy (SFG-VS)". In recent years, he developed the sub-wavenumber high resolution broadband SFG-VS (HR-BB-SFG-VS) and demonstrated its ability for obtaining intrinsic and accurate spectral lineshape in SFG-VS and other nonlinear spectroscopic techniques, such as the Femtosecond Stimulated Raman Spectroscopy (FSRS).  Prof. Wang was selected into the Hundred Talents Program of the Chinese Academy Sciences (1999-2002) and was awarded the Distinguished Young Investigator Fund of the National Natural Science Foundation of China (2005-2008). In 2012, he was elected a Fellow of the American Physical Society. He was also selected into the High-Level Overseas Talents Program of Shanghai in 2017 and the National High-Level Overseas Talents Program of China in 2018. For Attendees' Attention Seating is on a first come, first served basis.