Laser-Controlled Torsions: Four-Dimensional Theory and the Validity of Reduced Dimensionality Models

Grohmann, Thomas; Leibscher, M.; Seideman, Tamar

doi:10.1103/physrevlett.118.203201

Cited by 12 publications

(11 citation statements)

References 26 publications

(60 reference statements)

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“…This result, unexpected, since the Stark coupling Hamiltonian does not depend explicitly on the large amplitude torsional coordinate, stems from the fact that the torsional energy levels of a methyl group attached to a freely rotating hydroxyl group differ from those of a methyl group attached to an hydroxyl group aligned along the electric field. Unlike in biphenyl-like molecules [4][5][6][7][8][9][10][11][12][13][14], the electric field does not alter the torsional potential energy function, but changes a torsional kinetic energy term. In Section IV B, the effects of the strong short pulse are computed for several temperatures.…”

Section: Discussionmentioning

confidence: 99%

“…(13) is nonzero if ij = xx, yy, zz, or xz and reduces then to α 0 ij δ n,n . Equation (10) means that the matrix of the Stark Hamiltonian can be split into four blocks corresponding to the symmetry species of G 6 . Equation (12) shows that each block can be further split into several subblocks characterized by M .…”

Section: B Stark Coupling Hamiltonianmentioning

confidence: 99%

“…In these molecules, the two subunits are identical, or nearly identical, and the polarizability tensor, strongly dependent on their respective orientation, leads to a large amplitude torsional motion strongly coupled to the electric field through quadratic Stark effect. For this reason the behavior of these prototypical molecules when subject to a strong short electric field was extensively studied both theoretically [4][5][6][7][8][9][10][11] and experimentally [12][13][14]. In the second type of molecules, the two subunits are different and the polarizability tensor can be approximated by that of the larger one.…”

Section: Introductionmentioning

confidence: 99%

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Torsional control of the methyl group in methanol

et al. 2019

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Experimental and theoretical investigations of the field-free alignment of the non-rigid methanol molecule are reported. The molecule is subject to a 140 TW/cm 2 intensity laser pulse with a 100 fs duration. The experimental signal displays a constant permanent alignment and a fast decaying transient alignment consistent with a prolate-like molecule with (B + C)/2 on the order of 0.808 cm −1. The theoretical model takes into account the large amplitude internal rotation of the methyl group with respect to the hydroxyl group. In the case of a continuous wave laser field, a rotational alignment close to that of a rigid molecule is predicted. Torsional alignment also occurs even though there is no explicit dependence of the polarizability tensor on the angle of internal rotation. In the case of a strong short laser pulse, the theoretical approach shows that permanent and transient rotational alignment take place. The latter displays an exponential-like decay due to the high density of rotation-torsion levels. Torsional alignment also occurs and depends on the temperature. The theoretical model allows us to reproduce the experimental signal provided one component of the polarizability tensor is adjusted and dissipation effects due to molecular collisions are taken into account.

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Section: Discussionmentioning

confidence: 99%

Section: B Stark Coupling Hamiltonianmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Torsional control of the methyl group in methanol

et al. 2019

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“…The potential can be time-dependent, for example, for an investigation of laser-induced molecular alignment. 35,36 The dipole operators of the system are defined as μx = µ 0 sin( θ) cos( φ), μy = µ 0 sin( θ) sin( φ), and μz = µ 0 cos( θ), where µ 0 is the amplitude of the dipole for the liner-rigid rotor system. The rotor system is independently coupled to three heat baths in the x, y and z directions (a three-dimensional heat bath) through the functions of θ and φ.…”

Section: A the 3d-risb Modelmentioning

confidence: 99%

Open quantum dynamics of a three-dimensional rotor calculated using a rotationally invariant system-bath Hamiltonian: Linear and two-dimensional rotational spectra

Iwamoto

Tanimura

2019

The Journal of Chemical Physics

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We consider a rotationally invariant system-bath (RISB) model in three-dimensional space that is described by a linear rigid rotor independently coupled to three harmonic-oscillator baths through functions of the rotor's Euler angles. While this model has been developed to study the dielectric relaxation of a dipolar molecule in solvation as a problem of classical Debye relaxation, here we investigate it as a problem of open quantum dynamics. Specifically, the treatment presented here is carried out as an extension of a previous work [J. Chem. Phys, 149, 084110 (2018)], in which we studied a two-dimensional (2D) RISB model, to a three-dimensional (3D) RISB model. As in the 2D case, due to a difference in the energy discretization of the total Hamiltonian, the dynamics described by the 3D RISB model differ significantly from those described by the rotational Caldeira-Leggett (RCL) model. To illustrate the characteristic features of the quantum 3D rotor system described by angular momentum and magnetic quantum numbers, we derive a quantum master equation (QME) and hierarchical equations of motion (HEOM) for the 3D RISB model in the hightemperature case. Using the QME, we compute linear and two-dimensional (2D) rotational spectra defined by the linear and nonlinear response functions of the rotor dipole, respectively. The quantum transitions between the angular momentum states and magnetic states arising from polarized Stark fields as well as the system-bath interactions can be clearly observed in 2D rotational spectroscopy.

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“…Although purely quantum mechanical phenomenon, due to weak spectroscopic feature, tracking individual chemical bond break-up experimentally in dissociative or other chemical reaction mechanisms can be challenging both in gas or solution phase by traditional spectroscopies 6 . Spectroscopic detection of such torsion singularities will require advanced state-of-art single molecule based force or torque spectroscopy experiments 7 , 8 , 9 , 10 .…”

Section: Introductionmentioning

confidence: 99%

Quantum Signature of Anisotropic Singularities in Hydrogen Bond Breaking of Water Dimer

Ali¹,

Mezei²

2020

Preprint

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Abstract Molecular simulations from small molecules to large bio-macromolecules and polymer systems are routinely used to simulate thermodynamics properties of interests by molecular mechanics-based potentials. In a recent paper, via three different semi-empirical methods, we reported quantum singularities in molecular mechanics torsion potentials as signature of chemical bond break-up process revealed under experimental X-ray as broken chemical moieties. In this present work, applying first principle methods of Hartree-Fock, Density Functional as well as Moller-Plesset techniques we have reconfirmed the previous general predictions of singularities in the torsion potential for the case of water dimer that connects two water monomers by weak hydrogen bond. Due to quantum nature of chemical bond breaking process leading to break-point conditions in otherwise connected molecular topology aided by molecular mechanics based potentials, the singularities are also suggestive of large forces as onset in the bond-breaking process. We have presented the details of these novel interesting findings in this paper. These results of quantum singularities can have significant impacts to improve current force fields and can open up new areas we define as “Fracture Molecular Mechanics” or “Fracture Force Field” in overlap regions of molecular and quantum mechanics based approaches to explore and account for chemical bond-breaking mechanisms in molecular simulation techniques.

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Laser-Controlled Torsions: Four-Dimensional Theory and the Validity of Reduced Dimensionality Models

Cited by 12 publications

References 26 publications

Torsional control of the methyl group in methanol

Torsional control of the methyl group in methanol

Open quantum dynamics of a three-dimensional rotor calculated using a rotationally invariant system-bath Hamiltonian: Linear and two-dimensional rotational spectra

Quantum Signature of Anisotropic Singularities in Hydrogen Bond Breaking of Water Dimer

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