Peer-reviewed Publications |
Attal, L., Calvo, F., Falvo, C., & Parneix, P. (2024). Coherent state switching using vibrational polaritons in an asymmetric double-well potential. Phys. Chem. Chem. Phys., 2622(9), 753477–754477.
Résumé: The quantum dynamics of vibrational polaritonic states arising from the interaction of a bistable molecule with the quantized mode of a Fabry–Perot microcavity is investigated using a generic asymmetric double-well potential as a simplified one-dimensional model of a reactive molecule. After discussing the role of the light–matter coupling strength in the emergence of avoided crossings between polaritonic states, we investigate the possibility of using these crossings to trigger a dynamical switching of these states from one potential well to the other. Two schemes are proposed to achieve this coherent state switching, either by preparing the molecule in an appropriate vibrational excited state before inserting it into the cavity, or by applying a short laser pulse inside the cavity to obtain a coherent superposition of polaritonic states. The respective influences of dipole moment amplitude and potential asymmetry on the coherent switching process are also discussed.
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Attal, L., Falvo, C., Calvo, F., & Parneix, P. (2024). Modeling the dynamics of quantum systems coupled to large-dimensional baths using effective energy states. J. Chem. Phys., 16011(4), 04410700.
Résumé: The quantum dynamics of a low-dimensional system in contact with a large but finite harmonic bath is theoretically investigated by coarse-graining the bath into a reduced set of effective energy states. In this model, the couplings between the system and the bath are obtained from statistically averaging over the discrete, degenerate effective states. Our model is aimed at intermediate bath sizes in which non-Markovian processes and energy transfer between the bath and the main system are important. The method is applied to a model system of a Morse oscillator coupled to 40 harmonic modes. The results are found to be in excellent agreement with the direct quantum dynamics simulations presented in the work of Bouakline et al. [J. Phys. Chem. A 116, 11118–11127 (2012)], but at a much lower computational cost. Extension to larger baths is discussed in comparison to the time-convolutionless method. We also extend this study to the case of a microcanonical bath with finite initial internal energies. The computational efficiency and convergence properties of the effective bath states model with respect to relevant parameters are also discussed.
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Chahbazian, R., Martin-Drumel, M. - A., & Pirali, O. (2024). High-Resolution Spectroscopic Investigation of the CH2CHO Radical in the Sub-Millimeter Region. The Journal of Physical Chemistry A, 12811(2), 37033–37733.
Résumé: In this work, the pure rotational spectrum of the vinoxy radical (CH2CHO) has been studied at millimeter and sub-millimeter wavelengths (110–860 GHz). CH2CHO was produced by H-abstraction from acetaldehyde (CH3CHO) using atomic fluorine in a double-pass absorption cell at room temperature. A Zeeman-modulation spectrometer, in which an external magnetic field generated inside the absorption cell is amplitude-modulated, was used to record the pure rotational transitions of the radical. The recorded spectra are devoid of signals from closed-shell species, allowing for relatively fast acquisitions over wide spectral windows. Transitions involving values of the rotational quantum numbers N″ and Ka″ up to 41 and 18, respectively, were measured and combined with all available high-resolution literature data (both pure rotation and ground-state combination differences from ro-vibration) to greatly improve the modeling of the CH2CHO spectrum. The combined experimental line list is fit using a semirigid rotor Hamiltonian, and the results are compared to quantum chemical calculations. This laboratory study provides the spectroscopic information needed to search for CH2CHO in various interstellar environments, from cold (e.g., typically 10 K for dense molecular clouds) to warm (e.g., ∼200 K for hot corinos) objects.
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Mestdagh, J. - M., Barreau, L., & Poisson, L. (2024). Real-time dynamics of vibronic wavepackets within Rydberg and ion-pair states of molecular iodine. Phys Chem Chem Phys, .
Résumé: Real-time dynamics of vibrationally and electronically excited I_2 molecules has been investigated experimentally using the pump-probe technique. A 2-photon excitation was performed either at 269 nm or 266 nm. An electronic and vibrational wavepacket was built as coherent superposition of a few (269 nm excitation) or many (266 nm excitation) Rydberg states of the and series partly coupled with ion-pair states. The probe operated by ionisation or photodetachement. The energy and angular distribution of the resulting photoelectrons, I(+) photocations and I(-) photoanions were monitored. During the dynamics that is turned on by the pump excitation, the wavepacket splits and explores a variety of electronic states of Rydberg and ion-pair character. The experimental results were complemented by molecular dynamics calculations. This provided invaluable information to identify wavepacket motion along ion-pair potential energy curves.
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Zapata-Herrera, M., Rogez, B., Marguet, S., Dujardin, G., Boer-Duchemin, E., & Le Moal, E. (2024). Spectral shifts in tip-induced light from plasmonic nanoparticles in air. Phys. Rev. B, 109(15), 155433.
Résumé: In this article, we carry out an in-depth study of the scanning tunneling microscopy-induced luminescence spectra (STML) of individual plasmonic nanoparticles measured in air. When compared to the results of far-field light scattering measured under the same ambient conditions, the STML measurements show spectral shifts and peak broadening of hundreds of meV, even when a non-plasmonic tip is used for STML. We simulate the near-field excitation and the effect of the tip using the finite-element method and show that these effects alone cannot explain the spectral shifts and peak broadening observed for STML experiments in air. However, the experimental results are well reproduced in the numerical simulations if the screening effect of a water meniscus bridge present in the tip-nanoparticle gap is considered. Our results pave the way for finer interpretations of STML experiments in air, where ignoring this additional screening effect can lead to an incorrect mode assignment of the observed resonances.
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