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Vilà A, González M. Quantum dynamics of the Br 2 (B-excited state) photodissociation in superfluid helium nanodroplets: importance of the recombination process. Phys Chem Chem Phys 2022; 24:24353-24361. [PMID: 36178095 DOI: 10.1039/d2cp02984g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We have studied the Br2 photodissociation dynamics (B ← X electronic transition) of Br2(v = 0, X)@(4He)N doped nanodroplets (T = 0.37 K) at zero angular momentum, with N in the 100-1000 interval. To do this, we have used a quantum mechanical hybrid strategy proposed by us and, as far as we know, this is the second quantum dynamics study available on the photodissociation of molecules in superfluid helium nanodroplets. While the results obtained for some properties are qualitatively similar to those reported previously by us for the Cl2(B ← X) related case (in particular, the oscillating Br final velocity distribution which also arises from quantum interferences), large differences are evident in three key properties: the photodissociation mechanism and probability and the time scale of the process. This can be interpreted on the basis of the significantly lower excitation energy achieved by the Br2(B ← X) transition and the higher reduced mass of Br-Br in comparison to the chlorine case. The Br2(B) photodissociation dynamics is significantly more complex than that of Cl2(B) and leads to the fragmentation of the initial wave packet. Thus, the probability of non-dissociation is equal to 17, 18, 51, 85 and 100% for N = 100, 200, 300, 500 and 1000, respectively, while for chlorine this probability is equal to zero. In spite of the very large experimental difficulties that exist for obtaining nanodroplets with a well defined size, we hope that these results will encourage experimentalists to investigate these interesting systems.
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Affiliation(s)
- Arnau Vilà
- Departament de Ciència dels Materials i Química Física and IQTC, Universitat de Barcelona, Martí i Franquès, 1-11, 08028 Barcelona, Spain.
| | - Miguel González
- Departament de Ciència dels Materials i Química Física and IQTC, Universitat de Barcelona, Martí i Franquès, 1-11, 08028 Barcelona, Spain.
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García-Alfonso E, Barranco M, Bonhommeau DA, Halberstadt N, Pi M, Calvo F. Clustering, collision, and relaxation dynamics in pure and doped helium nanoclusters: Density- vs particle-based approaches. J Chem Phys 2022; 157:014106. [DOI: 10.1063/5.0091942] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The clustering, collision, and relaxation dynamics of pristine and doped helium nanodroplets is theoretically investigated in cases of pickup and clustering of heliophilic argon, collision of heliophobic cesium atoms, and coalescence of two droplets brought into contact by their mutual long-range van der Waals interaction. Three approaches are used and compared with each other. The He time-dependent density functional theory method considers the droplet as a continuous medium and accounts for its superfluid character. The ring-polymer molecular dynamics method uses a path-integral description of nuclear motion and incorporates zero-point delocalization while bosonic exchange effects are ignored. Finally, the zero-point averaged dynamics approach is a mixed quantum–classical method in which quantum delocalization is described by attaching a frozen wavefunction to each He atom, equivalent to classical dynamics with effective interaction potentials. All three methods predict that the growth of argon clusters is significantly hindered by the helium host droplet due to the impeding shell structure around the dopants and kinematic effects freezing the growing cluster in metastable configurations. The effects of superfluidity are qualitatively manifested by different collision dynamics of the heliophilic atom at high velocities, as well as quadrupole oscillations that are not seen with particle-based methods, for droplets experiencing a collision with cesium atoms or merging with each other.
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Affiliation(s)
- Ernesto García-Alfonso
- Laboratoire Collisions, Agrégats, Réactivité (LCAR), Université de Toulouse, CNRS, 31062 Toulouse, France
| | - Manuel Barranco
- Laboratoire Collisions, Agrégats, Réactivité (LCAR), Université de Toulouse, CNRS, 31062 Toulouse, France
- Department FQA, Facultat de Física, Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain
- Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, Barcelona, Spain
| | - David A. Bonhommeau
- Université de Reims Champagne Ardenne, CNRS, GSMA UMR 7331, 51100 Reims, France
| | - Nadine Halberstadt
- Laboratoire Collisions, Agrégats, Réactivité (LCAR), Université de Toulouse, CNRS, 31062 Toulouse, France
| | - Martí Pi
- Department FQA, Facultat de Física, Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain
- Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, Barcelona, Spain
| | - Florent Calvo
- Université Grenoble Alpes, CNRS, LIPHY, F38000 Grenoble, France
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Briant M, Mestdagh JM, Gaveau MA, Poisson L. Reaction dynamics within a cluster environment. Phys Chem Chem Phys 2022; 24:9807-9835. [PMID: 35441619 DOI: 10.1039/d1cp05783a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
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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Affiliation(s)
- Marc Briant
- Université Paris-Saclay, CEA, CNRS, LIDYL, 91191, Gif-sur-Yvette, France
| | | | - Marc-André Gaveau
- Université Paris-Saclay, CEA, CNRS, LIDYL, 91191, Gif-sur-Yvette, France
| | - Lionel Poisson
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, 91405, Orsay, France.
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Blancafort-Jorquera M, González M. Vibrational energy relaxation of a diatomic molecule in a superfluid helium nanodroplet: influence of the nanodroplet size, interaction energy and energy gap. Phys Chem Chem Phys 2021; 23:25961-25973. [PMID: 34783338 DOI: 10.1039/d1cp03629g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The influence of the nanodroplet size, molecule-helium interaction potential energy and ν = 1 - ν = 0 vibrational energy gap on the vibrational energy relaxation (VER) of a diatomic molecule (X2) in a superfluid helium nanodroplet [HeND or (4He)N; finite quantum solvent at T = 0.37 K] has been studied using a hybrid quantum approach recently proposed by us and taking as a reference the VER results on the I2@(4He)100 doped nanodroplet (Vilà et al., Phys. Chem. Chem. Phys., 2018, 20, 118, which corresponds to the first theoretical study on the VER of molecules embedded in a HeND). This has allowed us to obtain a deeper insight into the vibrational relaxation dynamics. The nanodroplet size has a very small effect on the VER, as this process mainly depends on the interaction between the molecule and the nanodroplet first solvation shell. Regarding the interaction potential energy and the energy gap, both factors play an important and comparable role in the VER time properties (global relaxation time, lifetime and transition time). As the former becomes stronger the relaxation time properties decrease in a significant way (their inverse follows a linear dependence with respect to the ν = 1 - ν = 0 coupling term) and they also decrease in a significant manner when the energy gap diminishes (linear dependence on the ν = 1 - ν = 0 energy difference). We expect that this study will motivate further work on the vibrational relaxation process in HeNDs.
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Affiliation(s)
- Miquel Blancafort-Jorquera
- Departament de Ciència dels Materials i Química Física and IQTC, Universitat de Barcelona, Martí i Franquès, 1-11, 08028 Barcelona, Spain.
| | - Miguel González
- Departament de Ciència dels Materials i Química Física and IQTC, Universitat de Barcelona, Martí i Franquès, 1-11, 08028 Barcelona, Spain.
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Alharzali N, Rodríguez-Segundo R, Prosmiti R. Modelling interactions of cationic dimers in He droplets: microsolvation trends in He nK 2+ clusters. Phys Chem Chem Phys 2021; 23:7849-7859. [PMID: 33220666 DOI: 10.1039/d0cp05406b] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We report the results of a detailed theoretical investigation of small K2+-doped He clusters. The structural characteristics and stabilities of such cations are determined from ab initio electronic structure calculations at the MRCI+Q level of theory. The underlying interactions show a multireference character and such effects are analyzed. The interaction potentials are constructed employing an interpolation technique within the inverse problem theory method, while the nuclear quantum effects are computed for the trimers, their spatial arrangements are discussed, and information was extracted on the orientational anisotropy of the forces. We found that energetically the most stable conformer corresponds to linear arrangements that are taking place under large amplitude vibrations, with high zero-point energy. We have further looked into the behavior of higher-order species with various He atoms surrounding the cationic dopant. By using a sum of potentials approach and an evolutionary programming method, we analyzed the structural stability of clusters with up to six He atoms in comparison with interactions energies obtained from MRCI+Q quantum chemistry computations. Structures containing Hen motifs that characterize pure rare gas clusters, appear for the larger K2+-doped He clusters, showing selective growth during the microsolvation process of the alkali-dimer cation surrounded by He atoms. Such results indicate the existence of local solvation microstructures in these aggregates, where the cationic impurity could get trapped for a short time, contributing to the slow ionic mobility observed experimentally in ultra-cold He-droplets.
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Affiliation(s)
- Nissrin Alharzali
- Institute of Fundamental Physics (IFF-CSIC), CSIC, Serrano 123, 28006 Madrid, Spain.
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Blancafort-Jorquera M, Vilà A, González M. Quantum-classical approach to the reaction dynamics in a superfluid helium nanodroplet. The Ne 2 dimer and Ne-Ne adduct formation reaction Ne + Ne-doped nanodroplet. Phys Chem Chem Phys 2019; 21:24218-24231. [PMID: 31661098 DOI: 10.1039/c9cp04561a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The dynamics of the Ne2 dimer and Ne-Ne adduct formation in a superfluid helium nanodroplet [(4He)N; T = 0.37 K], Ne + Ne@(4He)N→ Ne2@(4He)N'/Ne-Ne@(4He)N' + (N-N')4He with N = 500, has been investigated using a hybrid approach (quantum and classical mechanics (QM-CM) descriptions for helium and the Ne atoms, respectively) and taking into account the angular momentum of the attacking Ne atom, Ne(1). Comparison with zero angular momentum QM results of our own shows that the present results are similar to the quantum ones for the initial Ne(1) velocities (v0) of 500 and 800 m s-1 (the former one being the most probable velocity of Ne at 300 K), in all cases leading to the Ne2 dimer (re = 3.09 Å). However, significant differences appear below v0 = 500 m s-1, because in the QM-CM dynamics, instead of the dimer, a Ne-Ne adduct is formed (r0 = 5.45 Å). The formation of this adduct will probably dominate as the contribution to reactivity of angular momenta larger than zero is the leading one and angular momentum strongly acts against the Ne2 production. Angular momentum adds further difficulties in producing the dimer, since it makes it more difficult to remove the helium density between both Ne atoms to lead, subsequently, to the Ne2 molecule. Hence, the formation of the neon-neon adduct, Ne-Ne@(4He)N', clearly dominates the reactivity of the system, which results in the formation of a "quantum gel"/"quantum foam", because the two Ne atoms essentially maintain their identity inside the nanodroplet. Large enough Ne(1) initial angular momentum values can induce the formation of vortex lines by the collapse of superficial excitations (ripplons), but they occur with greater difficulty than in the case of the capture of the Ne atom by a non doped helium nanodroplet, due to the wave interferences induced by the Ne induced by the solvation layers of the Ne atom originally placed inside the nanodroplet. We hope that this work will encourage other researchers to investigate the reaction dynamics in helium nanodroplets, an interesting topic on which there are few studies available.
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Affiliation(s)
- Miquel Blancafort-Jorquera
- Departament de Ciència de Materials i Química Física and IQTC, Universitat de Barcelona, Martí i Franquès, 1-11, 08028 Barcelona, Spain.
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Blancafort-Jorquera M, Vilà A, González M. Rotational energy relaxation quantum dynamics of a diatomic molecule in a superfluid helium nanodroplet and study of the hydrogen isotopes case. Phys Chem Chem Phys 2019; 21:21007-21021. [PMID: 31528895 DOI: 10.1039/c9cp00952c] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The rotational energy relaxation (RER) of a molecule X2(j,mj) in a 4He superfluid nanodroplet [HeND or (4He)N; T = 0.37 K] has been investigated using a hybrid quantum dynamics approach recently proposed by us. As far as we know, this is the first theoretical study about rotational relaxation inside HeNDs, and here several (real and hypothetical) isotopes of H2 have been examined, in order to analyze the influence of the rotational constant Be of these fast rotors on the dynamics. The structure of the nanodroplet practically does not change during the RER process, which approximately takes place according to a cascade mechanism j → j - 2; j - 2 → j - 4; …; 2 → 0, and mj is conserved. The results are consistent with the very scarce estimated experimental data available. The lifetime of an excited rotational state (≈1.0-7.6 ns) increases when: (a) Be increases; (b) j increases; and (c) N decreases (above N = 100 there is a small influence of N on the lifetime). This also applies to the global relaxation time and transition time. The analysis of the influence of the coupling between the j and j - 2 rotational states (due to the X2-helium interaction) and the X2 angular velocity on the lifetime and related properties has been helpful to better understand the dynamics. In contrast to the RER results, for the vibrational energy relaxation (VER) in HeNDs, when the quantum number v increases a decrease is observed in the lifetime of the excited vibrational state. This difference can be interpreted taking into account that RER and VER are associated with very different types of motion. Besides, in VER the intermediate excited states show metastability, differing from the RER case. We hope that the present study will encourage more studies to be developed on the RER dynamics in HeNDs, a basic, interesting and difficult to study physical phenomenon about which we still know very little.
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Affiliation(s)
- Miquel Blancafort-Jorquera
- Departament de Ciència de Materials i Química Física and IQTC, Universitat de Barcelona, Martí i Franquès, 1-11, 08028 Barcelona, Spain.
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Coppens F, Ancilotto F, Barranco M, Halberstadt N, Pi M. Dynamics of impurity clustering in superfluid 4He nanodroplets. Phys Chem Chem Phys 2019; 21:17423-17432. [DOI: 10.1039/c9cp02789k] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Snapshot taken at 75 ps of the capture of six Ar atoms hitting a 4He5000 droplet at 100 m s−1.
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Affiliation(s)
- François Coppens
- Université Toulouse 3 and CNRS
- Laboratoire des Collisions
- Agrégats et Réactivité
- IRSAMC
- F-31062 Toulouse Cedex 09
| | - Francesco Ancilotto
- Dipartimento di Fisica e Astronomia “Galileo Galilei” and CNISM
- Università di Padova
- 35122 Padova
- Italy
- CNR-IOM Democritos
| | - Manuel Barranco
- Université Toulouse 3 and CNRS
- Laboratoire des Collisions
- Agrégats et Réactivité
- IRSAMC
- F-31062 Toulouse Cedex 09
| | - Nadine Halberstadt
- Université Toulouse 3 and CNRS
- Laboratoire des Collisions
- Agrégats et Réactivité
- IRSAMC
- F-31062 Toulouse Cedex 09
| | - Martí Pi
- Departament FQA
- Facultat de Física
- Universitat de Barcelona
- 08028 Barcelona
- Spain
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