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Vindel-Zandbergen P, Jiang J, Lewerenz M, Meier C, Barranco M, Pi M, Halberstadt N. Impulsive alignment of 4He-CH 3I: A theoretical study. J Chem Phys 2018; 149:124301. [PMID: 30278652 DOI: 10.1063/1.5048338] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We simulate the non-adiabatic laser alignment of the weakly bound 4He-CH3I complex based on a quantum mechanical wave packet calculation for a model He-CH3I interaction potential. Two different regimes are found depending on the laser intensity. At intensities typical of non-adiabatic alignment experiments, the rotational dynamics resembles that of the isolated molecule. This is attributed to the fact that after the initial prompt alignment peak the complex rapidly dissociates. The subsequent revival pattern is due to the free rotation of the molecule detached from the helium atom. It is superimposed to a flat background corresponding to ∼20% of the wave packet which remains bound, containing lower rotational excitation. At lower intensities, dissociation is avoided but the rotational excitation is not high enough to provide an efficient alignment and a broad non-regular structure is observed. Besides, the interaction of the He atom with the molecule quenches any possible alignment. These interpretations are based on the calculation of different observables related to the rotational motion. We compare our findings with recent experimental and theoretical results of non-adiabatic alignment of linear molecules solvated in helium nanodroplets or weakly interacting with one helium atom.
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Affiliation(s)
- Patricia Vindel-Zandbergen
- Laboratoire Collisions Agrégats Réactivité (LCAR), IRSAMC, Université de Toulouse, CNRS UMR 5589, Toulouse, France
| | - Ji Jiang
- Laboratoire de Modélisation et Simulation Multi Echelle, Equipe de Chimie Théorique, 5 Boulevard Descartes 77454, Marne-la Vallée Cedex 2, France
| | - Marius Lewerenz
- Laboratoire de Modélisation et Simulation Multi Echelle, Equipe de Chimie Théorique, 5 Boulevard Descartes 77454, Marne-la Vallée Cedex 2, France
| | - Christoph Meier
- Laboratoire Collisions Agrégats Réactivité (LCAR), IRSAMC, Université de Toulouse, CNRS UMR 5589, Toulouse, France
| | - Manuel Barranco
- Laboratoire Collisions Agrégats Réactivité (LCAR), IRSAMC, Université de Toulouse, CNRS UMR 5589, Toulouse, France
| | - Martí Pi
- Departament FQA, Facultat de Física, Universitat de Barcelona, Barcelona, Spain
| | - Nadine Halberstadt
- Laboratoire Collisions Agrégats Réactivité (LCAR), IRSAMC, Université de Toulouse, CNRS UMR 5589, Toulouse, France
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2
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Søndergaard AA, Shepperson B, Stapelfeldt H. Nonadiabatic laser-induced alignment of molecules: Reconstructing ⟨𝖼𝗈𝗌 𝟤 θ⟩ directly from ⟨𝖼𝗈𝗌 𝟤 θ 2D⟩ by Fourier analysis. J Chem Phys 2018; 147:013905. [PMID: 28688434 DOI: 10.1063/1.4975817] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present an efficient, noise-robust method based on Fourier analysis for reconstructing the three-dimensional measure of the alignment degree, ⟨cos2θ⟩, directly from its two-dimensional counterpart, ⟨cos2θ2D⟩. The method applies to nonadiabatic alignment of linear molecules induced by a linearly polarized, nonresonant laser pulse. Our theoretical analysis shows that the Fourier transform of the time-dependent ⟨cos2θ2D⟩ trace over one molecular rotational period contains additional frequency components compared to the Fourier transform of ⟨cos2θ⟩. These additional frequency components can be identified and removed from the Fourier spectrum of ⟨cos2θ2D⟩. By rescaling of the remaining frequency components, the Fourier spectrum of ⟨cos2θ⟩ is obtained and, finally, ⟨cos2θ⟩ is reconstructed through inverse Fourier transformation. The method allows the reconstruction of the ⟨cos2θ⟩ trace from a measured ⟨cos2θ2D⟩ trace, which is the typical observable of many experiments, and thereby provides direct comparison to calculated ⟨cos2θ⟩ traces, which is the commonly used alignment metric in theoretical descriptions. We illustrate our method by applying it to the measurement of nonadiabatic alignment of I2 molecules. In addition, we present an efficient algorithm for calculating the matrix elements of cos2θ2D and any other observable in the symmetric top basis. These matrix elements are required in the rescaling step, and they allow for highly efficient numerical calculation of ⟨cos2θ2D⟩ and ⟨cos2θ⟩ in general.
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Søndergaard AA, Zillich RE, Stapelfeldt H. Rotational dissociation of impulsively aligned van der Waals complexes. J Chem Phys 2017; 147:074304. [PMID: 28830172 DOI: 10.1063/1.4990616] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The nonadiabatic alignment dynamics of weakly bound molecule-atom complexes, induced by a moderately intense 300 fs nonresonant laser pulse, is calculated by direct numerical solution of the time-dependent Schrödinger equation. Our method propagates the wave function according to the coupled channel equations for the complex, which can be done in a very efficient and stable manner out to large times. We present results for two van der Waal complexes, CS2-He and HCCH-He, as respective examples of linear molecules with large and small moments of inertia. Our main result is that at intensities typical of nonadiabatic alignment experiments, these complexes rapidly dissociate. In the case of the CS2-He complex, the ensuing rotational dynamics resembles that of isolated molecules, whereas for the HCCH-He complex, the detachment of the He atom severely perturbs and essentially quenches the subsequent rotational motion. At intensities of the laser pulse ≲2.0 × 1012 W/cm2, it is shown that the molecule-He complex can rotate and align without breaking apart. We discuss the implications of our findings for recent experiments on iodine molecules solvated in helium nanodroplets.
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Affiliation(s)
| | - Robert E Zillich
- Institute for Theoretical Physics, Johannes Kepler University, Linz, Austria
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Moazzen-Ahmadi N, McKellar ARW, Fernández B, Farrelly D. The infrared spectrum of the Ne-C2D2 complex. J Chem Phys 2015; 143:204307. [PMID: 26627959 DOI: 10.1063/1.4936359] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Infrared spectra of Ne-C2D2 are observed in the region of the ν3 fundamental band (asymmetric C-D stretch, ≈2440 cm(-1)) using a tunable optical parametric oscillator to probe a pulsed supersonic slit jet expansion from a cooled nozzle. Like helium-acetylene, this system lies close to the free rotor limit, making analysis tricky because stronger transitions tend to pile up close to monomer (C2D2) rotation-vibration transitions. Assignments are aided by predicted rotational energies calculated from a published ab initio intermolecular potential energy surface. The analysis extends up to the j = 3←2 band, where j labels C2D2 rotation within the dimer, and is much more complete than the limited infrared assignments previously reported for Ne-C2H2 and Ne-C2HD. Two previous microwave transitions within the j = 1 state of Ne-C2D2 are reassigned. Coriolis model fits to the theoretical levels and to the spectrum are compared. Since the variations observed as a function of C2D2 vibrational excitation are comparable to those noted between theory and experiment, it is evident that more detailed testing of theory will require vibrational averaging over the acetylene intramolecular modes.
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Affiliation(s)
- N Moazzen-Ahmadi
- Department of Physics and Astronomy, University of Calgary, 2500 University Drive North West, Calgary, Alberta T2N 1N4, Canada
| | - A R W McKellar
- National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada
| | - Berta Fernández
- Department of Physical Chemistry and Center for Research in Biological Chemistry and Molecular Materials (CIQUS), University of Santiago de Compostela, E-15782 Santiago de Compostela, Spain
| | - David Farrelly
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322-0300, USA
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Moazzen-Ahmadi N, McKellar ARW, Fernández B, Farrelly D. The infrared spectrum of the He-C2D2 complex. J Chem Phys 2015; 142:084312. [PMID: 25725736 DOI: 10.1063/1.4913492] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Spectra of the helium-acetylene complex are elusive because this weakly bound system lies close to the free rotor limit. Previously, limited assignments of He-C2D2 transitions in the R(0) region of the ν3 fundamental band (≈2440 cm(-1)) were published. Here, new He-C2D2 infrared spectra of this band are obtained using a tunable optical parametric oscillator laser source to probe a pulsed supersonic slit jet expansion from a cooled nozzle, and the analysis is extended to the weaker and more difficult P(1) and R(1) regions. A term value approach is used to obtain a consistent set of "experimental" energy levels. These are compared directly with calculations using two recently reported ab initio intermolecular potential energy surfaces, which exhibit small but significant differences. Rovibrational energies for the He-C2H2 complex are also calculated using both surfaces. A Coriolis model, useful for predicting spectral intensities, is used to interpret the energy level patterns, and a comparison with the isoelectronic complex He-CO is made.
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Affiliation(s)
- N Moazzen-Ahmadi
- Department of Physics and Astronomy, University of Calgary, 2500 University Drive North West, Calgary, Alberta T2N 1N4, Canada
| | - A R W McKellar
- National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada
| | - Berta Fernández
- Department of Physical Chemistry, and Center for Research in Biological Chemistry and Molecular Materials (CIQUS), University of Santiago de Compostela, E-15782 Santiago de Compostela, Spain
| | - David Farrelly
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322-0300, USA
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Affiliation(s)
- Majed Chergui
- Ecole Polytechnique Fédérale de Lausanne, Laboratoire de Spectroscopie Ultrarapide, ISIC, FSB, Station 6, CH-1015 Lausanne, Switzerland.
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Galinis G, Cacho C, Chapman RT, Ellis AM, Lewerenz M, Mendoza Luna LG, Minns RS, Mladenović M, Rouzée A, Springate E, Turcu ICE, Watkins MJ, von Haeften K. Probing the structure and dynamics of molecular clusters using rotational wave packets. PHYSICAL REVIEW LETTERS 2014; 113:043004. [PMID: 25105616 DOI: 10.1103/physrevlett.113.043004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Indexed: 06/03/2023]
Abstract
Rotational wave packets of the weakly bound C(2)H(2)-He complex have been created using impulsive alignment. The coherent rotational dynamics were monitored for 600 ps enabling extraction of a frequency spectrum showing multiple rotational energy levels up to J = 4. spectrum has been combined with ab initio calculations to show that the complex has a highly delocalized structure and is bound only by ca. 7 cm(-1). The experiments demonstrate how highly featured rotational spectra can be obtained from an extremely cold environment where only the lowest rotational energy states are initially populated.
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Affiliation(s)
- Gediminas Galinis
- University of Leicester, Department of Physics & Astronomy, Leicester LE1 7RH, United Kingdom
| | - Cephise Cacho
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire OX11 0QX, United Kingdom
| | - Richard T Chapman
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire OX11 0QX, United Kingdom
| | - Andrew M Ellis
- University of Leicester, Department of Chemistry, Leicester LE1 7RH, United Kingdom
| | - Marius Lewerenz
- Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle, MSME UMR 8208 CNRS, 5 bd Descartes, 77454 Marne-la-Vallée, France
| | - Luis G Mendoza Luna
- University of Leicester, Department of Physics & Astronomy, Leicester LE1 7RH, United Kingdom
| | - Russell S Minns
- University of Southampton, Chemistry, Southampton SO17 1BJ, United Kingdom
| | - Mirjana Mladenović
- Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle, MSME UMR 8208 CNRS, 5 bd Descartes, 77454 Marne-la-Vallée, France
| | - Arnaud Rouzée
- Max Born Institute, Max Born Strasse 2A, 12489 Berlin, Germany
| | - Emma Springate
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire OX11 0QX, United Kingdom
| | - I C Edmond Turcu
- Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire OX11 0QX, United Kingdom
| | - Mark J Watkins
- University of Leicester, Department of Physics & Astronomy, Leicester LE1 7RH, United Kingdom
| | - Klaus von Haeften
- University of Leicester, Department of Physics & Astronomy, Leicester LE1 7RH, United Kingdom
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Chapman HN. Disruptive photon technologies for chemical dynamics. Faraday Discuss 2014; 171:525-43. [DOI: 10.1039/c4fd00156g] [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
A perspective of new and emerging technologies for chemical dynamics is given, with an emphasis on the use of X-ray sources that generate sub-picosecond pulses. The two classes of experimental techniques used for time-resolved measurements of chemical processes and their effects are spectroscopy and imaging, where the latter includes microscopy, diffractive imaging, and crystallography. X-Ray free-electron lasers have brought new impetus to the field, allowing not only temporal and spatial resolution at atomic time and length scales, but also bringing a new way to overcome limitations due to perturbation of the sample by the X-ray probe by out-running radiation damage. Associated instrumentation and methods are being developed to take advantage of the new opportunities of these sources. Once these methods of observational science have been mastered it should be possible to use the new tools to directly control those chemical processes.
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Affiliation(s)
- Henry N. Chapman
- Center for Free-Electron Laser Science
- DESY
- 22607 Hamburg, Germany
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