ABSTRACT
Novel X-ray pulse sources from free-electron lasers and high-harmonic generation setups enable the monitoring of molecular events on unprecedented temporal, spatial and energetic scales. The attosecond duration of X-ray pulses, their large bandwidth, tunable energy range, and the atomic selectivity of core X-ray excitations offer a uniquely high spatial and temporal selectivity for non linear spectroscopies. Recent developments in the design of X-ray spectroscopic signals reveal detailed information about the ultrafast passage through conical intersections. We show how the orbital angular momentum of twisted X-ray light can be leveraged to detect electronic and vibrational coherences and time evolving chirality emerging at conical intersections due to the bifurcation of molecular wavepackets. Multidimensional spectroscopy has been instrumental for probing dynamical processes in a wide variety of material systems ranging from atoms, molecules to biological complexes. These techniques traditionally rely on sequences of coherent laser pulses with electric fields with well defined envelopes and phases. Quantum light sources have been developed for broad applications such as quantum information processing, secure communication, and lithography. Employing quantum light in multidimensional spectroscopy is opening up many exciting opportunities to enhance the signal-to-noise ratio, improve the combined temporal, spatial, and spectral resolutions, and simplify nonlinear optical signals by selecting desired transition pathways. In second and third order signals, we show how photoelectron signals generated by time-energy entangled photon pairs can monitor ultrafast excited state dynamics of molecules with high joint spectral and temporal resolutions, not limited by the Fourier uncertainty of classical light. Two-entangled-photon absorption scales linearly with the pump intensity, allowing the study of fragile biological samples with low photon fluxes. Optical cavities provide another means for controlling the photophysics of molecules by making use of strong light– matter coupling without chemical modifications or strong external laser pulses. We present a quantum dynamical study on the charge migration in molecules by coupling to an optical cavity, which can activate and enhance the targeted charge migration modes that are suppressed in the bare molecule.
BIOGRAPHY
Shaul Mukamel, a Distinguished Professor of Chemistry and Physics & Astronomy at the University of California, Irvine, had received his Ph.D in 1976 from Tel Aviv University and held faculty positions at Rice University, the Weizmann Institute, and the University of Rochester. His research interests focus on the design of novel ultrafast multidimensional-coherent-optical spectroscopies for probing and controlling electronic and vibrational molecular dynamics in the condensed phase , and on spectroscopy with quantum light.He is the author of over 1000 publications and the textbook "Principles of Nonlinear Optical Spectroscopy. He is a Fellow of the American Physical Society , the Optical Society of America and an elected member of the American Academy of Arts & Sciences, the National Academy of Sciences, and the Indian National Science Academy. His recent awards include the Joseph O. Hirschfelder Prize in Theoretical Chemistry, Arthur L. Schawlow Prize in Laser Science, 2020, etc.
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