Physical Chemistry Seminar: Prof. Geoffrey A. Blake (California Institute of Technology)

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1315 Seminar Hall
@ 11:00 am

 

Title: Development and Applications of 2D THz-THz-Raman (TTR) Ultrafast Spectroscopy

Bio:

Prof. Blake (he/him/his) has over 40 years of experience in observational molecular astrophysics and in the development of laboratory instruments, with a focus on spectroscopic tools. Since 1988 he has mentored a team supported by NASA/NSF peer-reviewed research proposals, served on review panels, and held diverse positions of service and leadership at Caltech and in the scientific community. Over that time, 15+ graduate students and postdocs mentored with pride by Prof. Blake have moved on to the professoriate (majority female) and awarded highly competitive fellowships, with all but a few undergraduate research interns moving on to graduate programs. He has taught courses in both the Divisions of Chemistry & Chemical Engineering and Geological & Planetary Sciences throughout, including Caltech Core/undergraduate classes, and co-authored an ACS primer on Astrochemistry aimed at students and early career scholars, with now Prof. Olivia Wilkins (awarded the 2024 ACS Astrochemistry Thesis Prize). This highly interdisciplinary research and teaching environment enables group alums to pursue wide ranging careers that impact science and society.

Prof. Blake has served on advisory committees for the SURF and WAVE programs that seek to attract a talented, diverse group of undergrads to Caltech each summer. As Faculty Chair of Under- graduate Admissions (2006-2010) he worked to diversify our applicant pool and greatly increase the number of women and students of color admitted to Caltech, while as the Master of Student Houses (2009-2014) Prof. Blake led the development of support programs aimed at fostering the involvement and retention of minority students within the Caltech Residential Associate (RA) corps and student government. He continues to volunteer as a mentor to L.A. charter schools that serve predominantly first generation college and/or economically disadvantaged families. As Vice Chair and then Chair (2018-2020/2020-2022) of the Caltech Faculty Prof. Blake helped to guide the Institute’s response to the COVID-19 pandemic and oversaw the assessment of extensive Diversity, Equity, and Inclusion efforts at Caltech – especially programs that arose in response to the BlackLivesMatter movement.

Abstract:

Recent advances in nonlinear optical materials and phase matching schemes have enabled the efficient generation of near-transform-limited <100 fs TeraHertz (THz) pulses with field strengths well in excess of 1-10 MV/cm. Given the decade-spanning wavelength range generated, the elegant box geometries utilized for nonlinear 2D IR and other spectroscopies cannot be employed. Building on pioneering THz Kerr effect research by the Nelson group and the development of hybrid THz-Raman approaches by Hamm and co-workers, we have implemented nonlinear THz-THz-Raman (TTR) pulse sequences to probe the lowest energy molecular and phonon modes central to chemistry and materials science, and applied them to both liquids and to solid state samples important to nonlinear optics and quantum information science. The latest generation instrument now incorporates single shot detection techniques for the Raman probe, and this talk will highlight recent results, next steps in THz pulse generation and shaping, and the modeling + theoretical analyses required to untangle the many possible Feynman pathways that can contribute to the TTR signatures.

Keywords: “Ultrafast spectroscopy” “THz Science” “Quantum Information Science” “Molecular Liquids”

Host: Prof. Susanna Widicus-Weaver