Peer-reviewed Publications |
Autuori A, Platzer D, Lejman M, Gallician G, Maeder L, Covolo A, Bosse L, Dalui M, Bresteau D, Hergott JF, Tcherbakoff O, Marroux HJB, Loriot V, Lepine F, Poisson L, Taieb R, Caillat J, & Salieres P. (2022). Anisotropic dynamics of two-photon ionization: An attosecond movie of photoemission. Sci Adv, 8(12), eabl7594.
Résumé: Imaging in real time the complete dynamics of a process as fundamental as photoemission has long been out of reach because of the difficulty of combining attosecond temporal resolution with fine spectral and angular resolutions. Here, we achieve full decoding of the intricate angle-dependent dynamics of a photoemission process in helium, spectrally and anisotropically structured by two-photon transitions through intermediate bound states. Using spectrally and angularly resolved attosecond electron interferometry, we characterize the complex-valued transition probability amplitude toward the photoelectron quantum state. This allows reconstructing in space, time, and energy the complete formation of the photoionized wave packet.
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Briant M, Mestdagh JM, Gaveau MA, & Poisson L. (2022). Reaction dynamics within a cluster environment. Phys Chem Chem Phys, 24, 9807–9835.
Résumé: This perspective article reviews experimental and theoretical works where rare gas clusters and helium nanodroplets are used as a nanoreactor to investigate chemical dynamics in a solvent environment. A historical perspective is presented first followed by specific considerations on the mobility of reactants within these reaction media. The dynamical response of pure clusters and nanodroplets to photoexcitation is shortly reviewed before examining the role of the cluster (or nanodroplet) degrees of freedom in the photodynamics of the guest atoms and molecules.
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Lietard A, Piani G, Pollet R, Soep B, Mestdagh JM, & Poisson L. (2022). Excited state dynamics of normal dithienylethene molecules either isolated or deposited on an argon cluster. Phys Chem Chem Phys, 24, 10588–10598.
Résumé: Real-time dynamics of the electronically excited open-ring isomer of 1,2-bis(2-methylbenzo[b]thiophen-3-yl)perfluorocyclopentene (BTF6) and 1,2-bis(2,4-dimethyl-5-phenyl-3-thienyl)perfluorocyclopentene (PTF6) molecules was investigated using a set-up that associates a molecular beam, femtosecond lasers and velocity map imaging. The molecules were either free in the gas phase or bound to an argon cluster. DFT and TDDFT calculations were performed on BTF6. The calculated vertical excitation energies indicate an excitation by the pump laser towards a superposition of S5 and S6 states. The free molecule dynamics was found to follow a three wavepacket model. One describes the parallel conformer (P) of these molecules. It is unreactive with respect to the ring closure reaction which is responsible for the photochromic property of these molecules. It has no observable decay at the experiment time scale (up to 350 ps). The other two wavepackets describe the reactive antiparallel conformer (AP). They are formed by an early splitting of the wavepacket that was launched initially by the pump laser. They can be considered as generated by excitation of different, essentially uncoupled, deformation modes. They subsequently evolve along independent pathways. One is directed ballistically towards a conical intersection (CI) and decays through the CI to a potential energy surface where it can no longer be detected. The other fraction of the wavepacket decays also towards undetected states but in this case the driving mechanism is a non-adiabatic electronic relaxation within a potential well of the energy surfaces where it was launched. When BTF6 and PTF6 molecules are bound to an argon cluster, the same three wavepacket model applies. The vibronic relaxation timespan is enhanced by a factor 5 and a larger fraction of AP conformers follows this pathway. In contrast, the time constant associated with the ballistic movement is enhanced by only a factor of 2.
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Mandal S, Gatti F, Bindech O, Marquardt R, & Tremblay JC. (2022). Multidimensional stochastic dissipative quantum dynamics using a Lindblad operator. J Chem Phys, 156, 094109.
Résumé: In this paper, multidimensional dissipative quantum dynamics is studied within a system-bath approach in the Markovian regime using a model Lindblad operator. We report on the implementation of a Monte Carlo wave packet algorithm in the Heidelberg version of the Multi-Configuration Time-Dependent Hartree (MCTDH) program package, which is henceforth extended to treat stochastic dissipative dynamics. The Lindblad operator is represented as a sum of products of one-dimensional operators. The new form of the operator is not restricted to the MCTDH formalism and could be used with other multidimensional quantum dynamical methods. As a benchmark system, a two-dimensional coupled oscillators model representing the internal stretch and the surface-molecule distance in the O2/Pt(111) system coupled to a Markovian bath of electron-hole-pairs is used. The simulations reveal the interplay between coherent intramolecular coupling due to anharmonic terms in the potential and incoherent relaxation due to coupling to an environment. It is found that thermalization of the system can be approximately achieved when the intramolecular coupling is weak.
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Matthaei CT, Mukhopadhyay DP, Roder A, Poisson L, & Fischer I. (2022). Photodissociation of the trichloromethyl radical: photofragment imaging and femtosecond photoelectron spectroscopy. Phys Chem Chem Phys, 2(24), 928–940.
Résumé: Halogen-containing radicals play a key role in catalytic reactions leading to stratospheric ozone destruction, thus their photochemistry is of considerable interest. Here we investigate the photodissociation dynamics of the trichloromethyl radical, CCl3 after excitation in the ultraviolet. While the primary processes directly after light absorption are followed by femtosecond-time resolved photoionisation and photoelectron spectroscopy, the reaction products are monitored by photofragment imaging using nanosecond-lasers. The dominant reaction is loss of a Cl atom, associated with a CCl2 fragment. However, the detection of Cl atoms is of limited value, because in the pyrolysis CCl2 is formed as a side product, which in turn dissociates to CCl + Cl. We therefore additionally monitored the molecular fragments CCl2 and CCl by photoionisation at 118.2 nm and disentangled the contributions from various processes. A comparison of the CCl images with control experiments on CCl2 suggest that the dissociation to CCl + Cl2 contributes to the photochemistry of CCl3.
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