Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session R26: Chemical Physics in Strong Fields ILive
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Sponsoring Units: DCP Chair: Amy Mullin, University of Maryland, College Park |
Thursday, March 18, 2021 8:00AM - 8:12AM Live |
R26.00001: On-the-fly ab initio semiclassical evaluation of third-order response functions for two-dimensional electronic spectroscopy Tomislav Begusic, Jiri Vanicek Ab initio computation of two-dimensional electronic spectra is an expanding field, whose goal is improving upon simple, few-dimensional models often employed to explain experiments [1]. Here, we propose an accurate and computationally affordable approach [2], based on the single-trajectory semiclassical thawed Gaussian approximation [3], to evaluate two-dimensional electronic spectra. The method is exact for arbitrary harmonic potentials with mode displacement, changes in the mode frequencies, and inter-mode coupling, but can also account partially for the anharmonicity of the potential energy surfaces. We test its accuracy on a set of model Morse potentials and use it to study anharmonicity and Duschinsky effects on the linear and two-dimensional electronic spectra of phenol. We find that in this molecule, the anharmonicity effects are weak, whereas the mode-mode coupling and the changes in the mode frequencies must be included in accurate simulations. In contrast, the widely used displaced harmonic oscillator model captures only the basic physics of the problem but fails to reproduce the correct vibronic lineshape. |
Thursday, March 18, 2021 8:12AM - 8:24AM Live |
R26.00002: Rotationally-resolved cavity-enhanced 2DIR spectroscopy Grzegorz Kowzan, Myles Silfies, Neomi Ashwita Lewis, Thomas K Allison Detection of trace amounts of molecules in multi-species mixtures is important for many purposes, ranging from chemical dynamics in complex environments to breath analysis. 2DIR spectroscopy is a powerful tool for studying both molecular structure and dynamics. It can provide better selectivity than linear spectroscopy due to the extra degrees of freedom for distinguishing the components of a complex mixture. Application of 2DIR spectroscopy to trace-gas detection has been hindered by insufficient sensitivity and resolution of the technique. Cavity-enhancement methods for ultrafast nonlinear spectroscopy using frequency combs can provide high-resolution and high sensitivity simultaneously [1]. |
Thursday, March 18, 2021 8:24AM - 8:36AM Live |
R26.00003: Anharmonic vibrational polaritons in the ultrastrong coupling regime: Nonlinear spectroscopy and chemical reactivity Johan Triana, Felipe Herrera Light-matter interaction of molecular vibrations with confined infrared fields is a powerful resource for controlling the spectroscopy and chemical reactivity of molecular materials [1]. Experiments show that the properties of vibrational polariton states can strongly depend on the detailed internal structure of the coupled molecules [2]. We introduce fully-quantum theory for the coupling of a Morse oscillator with an infrared cavity, taking into account both transition and permanent molecular dipole moments [3], and show that at the onset of ultrastrong coupling, polar molecular modes can spontaneously dissociate when placed inside a cavity [4]. The same theory has been successfully used to describe ultrafast polariton-to-polariton transitions in two-dimensional infrared cavity spectroscopy [5]. Our work thus offers mechanistic insights on the spectroscopy and chemistry hybrid vibration-cavity states. |
Thursday, March 18, 2021 8:36AM - 8:48AM Live |
R26.00004: Atomistic simulation of vibrational strong light-matter interactions Tao Li, Abraham Nitzan, Joseph E Subotnik Here, we introduce how to run classical atomisitic simulation under vibrational strong coupling (VSC), i.e., when a vibrational mode of a large ensemble of realistic molecules is strongly coupled to a cavity mode. This cavity molecular dynamcis (CavMD) scheme not only recover optical spectrum such as the asymmetric Rabi splitting, but also demonstrate many intriguing nonequilibrium dynamics such as vibrational polariton relaxation and polariton-enhanced multiphoton absorption, which can be used to diectly compare with or predict VSC experiments in Fabry-Perot mirocavities. |
Thursday, March 18, 2021 8:48AM - 9:00AM Live |
R26.00005: Probing the relaxation channels of metalloporphyrin cavity polaritons with ultrafast dynamical spectroscopy Aleksandr Avramenko, Aaron S Rury A photochemical reaction involves the reactant moving from its own excited state potential energy surface to the ground state potential energy surface of the product. Control over excited state dynamics remains an unfulfilled goal of the chemical physics community. In this study we examine how the formation of molecular polaritons impacts the molecular dynamics of a ZnTPP molecule strongly coupled to a cavity mode. Cavity polaritons were formed by coupling the Soret transition of ZnTPP to the photons of a Fabry Perot micro cavity. We then proceed to probe the non radiative transition between the S2 -S1 excited states using transient spectroscopy measurements as a function of the collective Rabi splitting. We find inverse relationships between both the rate and efficiency of S2-S1 internal conversion and the Rabi splitting. We propose that interpolariton decay channels increasingly control the rate of internal conversion as the Rabi splitting approaches the energy of the vibrations involved in non-radiative relaxation of excited state population to the S1 state. Our research suggests that researchers must carefully understand the photphysics of molecules strongly coupled to cavity photons to enable their application to next generation of photochemical technologies. |
Thursday, March 18, 2021 9:00AM - 9:12AM Live |
R26.00006: Thermo-Optical Nonlinearity of Metallic Nanoparticle(s) Ieng-Wai Un, Yonatan Sivan The thermal effect is known to be one of the strongest mechanisms of optical nonlinearity but is usually avoided under ultrafast illumination. In this work, quite different from many previous studies in the ultrafast region, we study the thermo-optical nonlinearity of a single metal nanoparticle and many-nanoparticle composite under continuous-wave illumination. We show [Gurwich & Sivan, Phys. Rev. E, 2017; Sivan & Chu, Nanophotonics, 2017; Un & Sivan, Phys. Rev. Mater., 2020] that the thermo-optical nonlinearity of single metal nanoparticle systems strongly depends on the illumination wavelength and the nanoparticle size. The results of the single-nanoparticle system are then used to study the thermo-optical nonlinearity of many-nanoparticle composites. We show that different from the case of a single nanoparticle, the thermo-optical nonlinearity of the composite is strongly sensitive to the thermal conductivity of the host material only. Since photo-thermal effects were shown [Dubi et al., Chem. Sci., 2020] to be responsible for observations of faster chemical reactions, our results can be used to interpret correctly the differences in chemical reaction enhancements originating from the thermo-optical nonlinearity at different illumination intensities. |
Thursday, March 18, 2021 9:12AM - 9:24AM Live |
R26.00007: Long-distance excitation energy transfer under strong laser drive Xuanhua Wang
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Thursday, March 18, 2021 9:24AM - 9:36AM Live |
R26.00008: Basis set truncation further clarifies vibrational coherence spectra Daniel Turner, Paul Arpin
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Thursday, March 18, 2021 9:36AM - 9:48AM Live |
R26.00009: Transient studies of vibration-cavity polaritons Elizabeth Ryland, Andrea Grafton, Jeffrey C Owrutsky, Blake Simpkins, Adam Dunkelberger Vibration-cavity polaritons, which are produced by strong coupling between an optical cavity and a molecular vibration, have been shown to modify chemical reaction rates and branching ratios. However, the underlying mechanisms for the observed effects are poorly understood. In order to gain insight into how these polaritons might alter molecular processes, we have used ultrafast pump-probe and two-dimensional infrared (2DIR) spectroscopies to characterize coherent and incoherent polariton excited state behaviors. Our earlier studies on tungsten hexacarbonyl (W(CO)6) strongly coupled to a Fabry-Pérot cavity demonstrated that much of the response is due to reservoir or uncoupled excited state absorption as well as polariton contraction. In recent studies, we have used 2DIR and spectrally filtered pump-probe studies on the nitroprusside anion (Fe(CN)5NO2-) in methanol to determine the transition frequencies and dynamics of polariton excited states allowing us to extract polariton dephasing timescales, which follow those of the cavity and molecule, as well as incoherent polariton population which decays at a significantly longer timescale. These studies reveal novel aspects of vibration-cavity polaritons that may reveal how they impact energy transfer, photophysics, and chemistry. |
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