Peer-reviewed Publications |
Aerts, A., Brown, A., & Gatti F. (2022). Intramolecular vibrational redistribution in formic acid and its deuterated forms. J Chem Phys, 157, 014306.
Résumé: The intramolecular vibrational relaxation dynamics of formic acid and its deuterated isotopologues is simulated on the full-dimensional potential energy surface of Richter and Carbonniere [J. Chem. Phys. 148, 064303 (2018)] using the Heidelberg MCTDH package. We focus on couplings with the torsion vibrational modes close to the trans-cis isomerization coordinate from the dynamics of artificially excited vibrational mode overtones. The bright C-O stretch vibrational mode is coupled to the out-of-the plane torsion mode in HCOOH, where this coupling could be exploited for laser-induced trans-to-cis isomerization. Strong isotopic effects are observed: deuteration of the hydroxyl group, i.e., in HCOOD and DCOOD, destroys the C-O stretch to torsion mode coupling whereas in DCOOH, little to no effect is observed.
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Albers, H., Corgier, R., Herbst, A., Rajagopalan, A., Schubert, C., Vogt, C., Woltmann, M., Lämmerzahl, C., Herrmann, S., Charron, E., Ertmer, W., Rasel, E. M., Gaaloul, N., & Schlippert, D. (2022). All-optical matter-wave lens using time-averaged potentials. Commun Phys, 5(60).
Résumé: The precision of matter-wave sensors benefits from interrogating large-particle-number atomic ensembles at high cycle rates. Quantum-degenerate gases with their low effective temperatures allow for constraining systematic errors towards highest accuracy, but their production by evaporative cooling is costly with regard to both atom number and cycle rate. In this work, we report on the creation of cold matter-waves using a crossed optical dipole trap and shaping them by means of an all-optical matter-wave lens. We demonstrate the trade off between lowering the residual kinetic energy and increasing the atom number by reducing the duration of evaporative cooling and estimate the corresponding performance gain in matter-wave sensors. Our method is implemented using time-averaged optical potentials and hence easily applicable in optical dipole trapping setups.
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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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Dowek, D., & Decleva, P. (2022). Trends in angle-resolved molecular photoelectron spectroscopy. Phys Chem Chem Phys, 40(24), 24614–24654.
Résumé: The field of angle-resolved molecular photoelectron spectroscopy is reviewed, with emphasis on foundations and most recent applications in different regimes of light-matter interaction. The basic formalism underlying one-photon electron angular distributions is presented, from the primary molecular frame (MF) photoemission i.e. emission from fully oriented molecules to laboratory frame (LF) observables produced from randomly oriented targets, extensions to multiphoton and strong field processes being briefly described, followed by a survey of current quantum mechanical computational approaches. The description of experimental developments is focused on the advancements in two major instrumentation fields for angle-resolved PES of molecules in the last two decades, namely charged-particle imaging spectrometers and adiabatically or impulsively laser-induced molecular alignment, together with their interplay with the remarkable characteristics achieved nowadays by the ionizing light sources and the challenging control of complex molecules in the gas phase. Aspects and applications of LF angular observables from unoriented targets are presented, with contemporary applications, especially as probes of the target electronic structure, including higher angular observables, in particular photoelectron circular dichroism (PECD) from chiral molecules, which is confirmed as a powerful chiral technique, and higher terms arising from multiphoton or non-dipole terms. Molecular frame photoelectron angular distributions (MFPADs), which stand out as the most complete observables of molecular photoionization stereodynamics in different excitation regimes, now broadly extended to characterize molecular structure and dynamics, are then discussed stemming from fully oriented molecules tackled by electron-ion momentum coincidence techniques, or from laser aligned samples. Finally, novel developments and challenging perspectives, notably the implementation of PAD in time-resolved schemes at ultrashort time scales, high energy, and high intensity regimes are drawn.
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Gaaloul, N., Meister, M., Corgier, R., Pichery, A., Boegel, P., Herr, W., Ahlers, H., Charron, E., Williams, J. R., Thompson, R. J., Schleich, W. P., Rasel, E. M., & Bigelow, N. P. (2022). A space-based quantum gas laboratory at picokelvin energy scales. Nat Commun, (13), 7989.
Résumé: Ultracold quantum gases are ideal sources for high-precision space-borne sensing as proposed for Earth observation, relativistic geodesy and tests of fundamental physical laws as well as for studying new phenomena in many-body physics during extended free fall. Here we report on experiments with the Cold Atom Lab aboard the International Space Station, where we have achieved exquisite control over the quantum state of single (87)Rb Bose-Einstein condensates paving the way for future high-precision measurements. In particular, we have applied fast transport protocols to shuttle the atomic cloud over a millimeter distance with sub-micrometer accuracy and subsequently drastically reduced the total expansion energy to below 100 pK with matter-wave lensing techniques.
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Han, S., Schroder, M., Gatti, F., Meyer, H. - D., Lauvergnat, D., Yarkony DR, & Guo H. (2022). Representation of Diabatic Potential Energy Matrices for Multiconfiguration Time-Dependent Hartree Treatments of High-Dimensional Nonadiabatic Photodissociation Dynamics. J Chem Theory Comput, 18(8), 4627–4638.
Résumé: Conventional quantum mechanical characterization of photodissociation dynamics is restricted by steep scaling laws with respect to the dimensionality of the system. In this work, we examine the applicability of the multi-configurational time-dependent Hartree (MCTDH) method in treating nonadiabatic photodissociation dynamics in two prototypical systems, taking advantage of its favorable scaling laws. To conform to the sum-of-product form, elements of the ab initio diabatic potential energy matrix (DPEM) are re-expressed using the recently proposed Monte Carlo canonical polyadic decomposition method, with enforcement of proper symmetry. The MCTDH absorption spectra and product branching ratios are shown to compare well with those calculated using conventional grid-based methods, demonstrating its promise for treating high-dimensional nonadiabatic photodissociation problems.
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Ismail, I., Khalal, M. A., Huttula, M., J ankala, K., Bizau, J. - M., Cubaynes, D., Hikosaka, Y., Bucar, K., Zitnik, M., Andric, L., Lablanquie, P., Palaudoux, J., & Penent, F. (2022). A modified magnetic bottle electron spectrometer for the detection of multiply charged ions in coincidence with all correlated electrons: decay pathways to Xe(3+) above xenon-4d ionization threshold. Phys Chem Chem Phys, 34(24), 20219–20227.
Résumé: Single-photon multiple photoionization results from electron correlations that make this process possible beyond the independent electron approximation. To study this phenomenon experimentally, the detection in coincidence of all emitted electrons is the most direct approach. It provides the relative contribution of all possible multiple ionization processes, the energy distribution between electrons that can reveal simultaneous or sequential mechanisms, and, if possible, the angular correlations between electrons. In the present work, we present a new magnet design of our magnetic bottle electron spectrometer that allows the detection of multiply charged Xe(n+) ions in coincidence with n electrons. This new coincidence detection allows more efficient extraction of minor channels that are otherwise masked by random coincidences. The proof of principle is provided for xenon triple ionization.
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J.-P. Mosnier, E. T. Kennedy, D. Cubaynes, J.-M. Bizau, S. Guilbaud, M. F. Hasoğlu, C. Blancard, & T. W. Gorczyca. (2022). L-shell photoionization of Mg-like S4+ ions in ground and metastable states: Experiment and theory. Phys. Rev. A, (106), 033113.
Résumé: We report measurements of the absolute photoionization cross sections of magnesiumlike S4+ over the 158–280 eV photon energy range. The experiments were performed with the multianalysis ion apparatus at the SOLEIL synchrotron radiation facility. Single- and double-ionization ion yields produced by the photoionization of the 2p subshell of the S4+ both from the 2p63s21S0 ground state and the 2p53s3p3P0,1,2 metastable levels were observed, as well as 2s excitations. Theoretical calculations of the photoionization cross sections were carried out using multiconfiguration Dirac-Fock and R-matrix computer codes and the results are compared with the experimental data. While in general reasonably good agreement was found, notable differences in the strengths and positions of predicted resonances were observed and significant systematic energy shifts of the theoretical predictions were required.
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Jarraya, M., Bellili, A., Barreau, L., Cubaynes, D., Garcia, G. A., Poisson L, & Hochlaf M. (2022). Probing the dynamics of the photo-induced decarboxylation of neutral and ionic pyruvic acid. Faraday Discuss, 238, 266–294.
Résumé: The dynamics of the electronically excited pyruvic acid (PA) and of its unimolecular decomposition upon single photon ionisation are investigated by means of a table top fs laser and VUV synchrotron radiation. The latter is coupled with photo-ion/photo-electron coincidence acquisition devices that allow the identification of the ionic products coming from state-to-state fragmentation upon ionisation. The fs-based setup provides time-resolved mass spectra with 266 nm (= 4.661 eV) excitation and an 800 nm multiphoton probe. For interpretation, we carried out theoretical computations using a composite scheme combining density functional theory full molecular geometric optimisation and post-Hartree-Fock correction inclusion. We therefore determined the neutral and ionic species formed during these experiments and the corresponding dissociation channels. Although several PA isomers are found, we show that solely the most stable isomer of PA (i.e. Tc) is present in the molecular beam prior to ionisation. We determined its adiabatic ionisation energy (AIE = 10.031 +/- 0.005 eV). The fragmentation of the Tc(+) ion occurs at approximately 0.4 eV above the threshold and it is dominated by the CC bond breaking channel, forming the HOCO fragment in conjunction with the CH3CO(+) ion. The decarboxylation of Tc(+) channels has a minor contribution, although they are more favourable thermodynamically. These findings are in contrast with the dominance of decarboxylation while fragmenting Tc populated in the S1-S3 states. For explanation, we invoke an indirect process populating first a short lived autoionising neutral state located in energy at the HOCO + CH3CO(+) dissociation limit. Later on, fragmentation occurs, followed by autoionisation. On the other hand, the fs-based experiment does not reveal any appreciable dynamics for the Tc isomer of PA after a 266 nm excitation because of non-favourable Franck-Condon factors at this energy. In sum, our work highlights the importance of the couplings between the parent ion vibrational modes and the dissociative channels in the vicinity of the loss ionic fragmentation thresholds.
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Laurent, J., Bozek, J., Briant, M., Carcabal, P., Cubaynes, D., Milosavljevic, A., Puttner, R., Shafizadeh, N., Simon, M., Soep, B., & Goldsztejn, G. (2022). Consistent characterization of the electronic ground state of iron(II) phthalocyanine from valence and core-shell electron spectroscopy. Phys Chem Chem Phys, 4(24), 2656–2663.
Résumé: We studied the iron(II) phthalocyanine molecule in the gas-phase. It is a complex transition organometallic compound, for which, the characterization of its electronic ground state is still debated more than 50 years after the first published study. Here, we show that to determine its electronic ground state, one needs a large corpus of data sets and a consistent theoretical methodology to simulate them. By simulating valence and core-shell electron spectra, we determined that the ground state is a (3)E(g) and that the ligand-to-metal charge transfer has a large influence on the spectra.
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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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Mainali, S., Gatti, F., & Atabek, O. (2022). Laser control strategies in full-dimensional funneling dynamics: The case of pyrazine. Chin Opt Lett, 20(10), 100007.
Résumé: Motivated by the major role funneling dynamics plays in light-harvesting processes, we built some laser control strategies inspired from basic mechanisms such as interference and kicks, and applied them to the case of pyrazine. We are studying
the internal conversion between the two excited states, the highest and directly reachable from the initial ground state being considered as a donor and the lowest as an acceptor. The ultimate control objective is the maximum population
deposit in the otherwise dark acceptor from a two-step process: radiative excitation of the donor, followed by a conical-intersection-mediated funneling towards the acceptor. The overall idea is to first obtain the control field param-
eters (individual pulses leading frequency and intensity, duration, and inter-pulse time delay) for tractable reduced dimensional models basically describing the conical intersection branching space. Once these parameters are optimized, they are
fixed and used in full-dimensional dynamics describing the electronic population transfer. In the case of pyrazine, the reduced model is four-dimensional, whereas the full dynamics involves 24 vibrational modes. Within experimentally achiev-
able electromagnetic field requirements, we obtain a robust control with about 60% of the ground state population deposited in the acceptor state, while about 16% remains in the donor. Moreover, we anticipate a possible transposition to the
control of even larger molecular systems, for which only a small number of normal modes are active, among all the others acting as spectators in the dynamics.
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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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Mandal, S., Gatti, F., Bindech, O., Marquardt, R., & Tremblay, J. C. (2022). Stochastic multi-configuration time-dependent Hartree for dissipative quantum dynamics with strong intramolecular coupling. J Chem Phys, 157(144105).
Résumé: In this article, we explore the dissipation dynamics of a strongly coupled multidimensional system in contact with a Markovian bath, following a system-bath approach. We use in this endeavor the recently developed stochastic multi-configuration time-dependent Hartree approach within the Monte Carlo wave packet formalism [S. Mandal et al., J. Chem. Phys. 156, 094109 (2022)]. The method proved to yield thermalized ensembles of wave packets when intramolecular coupling is weak. To treat strongly coupled systems, new Lindblad dissipative operators are constructed as linear combinations of the system coordinates and associated momenta. These are obtained by a unitary transformation to a normal mode representation, which reduces intermode coupling up to second order. Additionally, we use combinations of generalized raising/lowering operators to enforce the Boltzmann distribution in the dissipation operators, which yield perfect thermalization in the harmonic limit. The two ansatz are tested using a model two-dimensional Hamiltonian, parameterized to disentangle the effects of intramolecular potential coupling, of strong mode mixing observed in Fermi resonances, and of anharmonicity.
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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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Schroder, M., Gatti F, Lauvergnat D, Meyer HD, & Vendrell O. (2022). The coupling of the hydrated proton to its first solvation shell. Nat Commun, 13(6170).
Résumé: The Zundel and Eigen cations play an important role as intermediate structures for proton transfer processes in liquid water. In the gas phase they exhibit radically different infrared (IR) spectra. The question arises: is there a least common denominator structure that explains the IR spectra of both, the Zundel and Eigen cations, and hence of the solvated proton? Full dimensional quantum simulations of these protonated cations demonstrate that two dynamical water molecules and an excess proton constitute this fundamental subunit. Embedded in the static environment of the parent Eigen cation, this subunit reproduces the positions and broadenings of its main excess-proton bands. In isolation, its spectrum reverts to the well-known Zundel ion. Hence, the dynamics of this subunit polarized by an environment suffice to explain the spectral signatures and anharmonic couplings of the solvated proton in its first solvation shell.
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Song, Q., Zhang, X., Gatti, F., Miao, Z., Zhang, Q., & Meng, Q. (2022). Multilayer Multiconfiguration Time-Dependent Hartree Study on the Mode-/Bond-Specific Quantum Dynamics of Water Dissociation on Cu(111). J Phys Chem A, 126(36), 6047–6058.
Résumé: In this work, full-dimensional (9D) quantum dynamics calculations on mode-/bond-specific surface scattering of a water molecule on a copper (111) rigid surface are performed through the multilayer multiconfiguration time-dependent Hartree (ML-MCTDH) method. To easily perform the ML-MCTDH calculations on such a triatomic molecule-surface system, we first choose specific Jacobi coordinates as a set of coordinates of water. Next, to efficiently perform the 9D ML-MCTDH wavepacket propagation, the potential energy surface is transferred to a canonical polyadic decomposition form with the aid of a Monte Carlo-based method. Excitation-specific dissociation probabilities of H2O on Cu(111) are computed, and mode-/bond-specific dynamics are demonstrated by comparison with a probability curve computed for a water molecule in the ground state. The dependence of the dissociation probability of the initial state of H2O is studied, and it is found that the excitation-specific dissociation probabilities can be divided into three groups. We find that the vibrationally excited states enhance the dissociation reactivity of H2O, while the rotationally excited states hardly influence it.
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Vigneau, J. - N., Nguyen-Dang, T. - T., Charron, E., & Atabek, O. (2022). Strong-field molecular ionization beyond the single active electron approximation. J Chem Phys, 157, 134304.
Résumé: This work explores quantitative limits to the single-active electron approximation, often used to deal with strong-field ionization and subsequent attosecond dynamics. Using a time-dependent, multiconfiguration approach, specifically the time-dependent configuration interaction method, we solve the time-dependent Schrodinger equation for the two-electron dihydrogen molecule with the possibility of tuning at will the electron-electron interaction by an adiabatic switch-on/switch-off function. We focus on signals of the single ionization of H(2) under a strong near-infrared, four-cycle, linearly polarized laser pulse of varying intensity and within a vibrationally frozen molecular model. The observables we address are post-pulse total ionization probability profiles as a function of the laser peak intensity. Three values of the internuclear distance R taken as a parameter are considered, R = R(eq) = 1.4 a.u. for the equilibrium geometry of the molecule, R = 5.0 a.u. for an elongated molecule, and R = 10.2 a.u. for a dissociating molecule. The most striking observation is the non-monotonous behavior of the ionization probability profiles at intermediate elongation distances with an instance of enhanced ionization and one of partial ionization quenching. We give an interpretation of this in terms of a resonance-enhanced-multiphoton ionization mechanism with interfering overlapping resonances resulting from excited electronic states.
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