Level-dependent damping in intermolecular vibrations: Linear spectroscopy

Farrer, Richard A.; Loughnane, Brian J.; Deschenes, Laura A.; Fourkas, John T.

doi:10.1063/1.473715

Cited by 61 publications

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References 59 publications

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“…In vibrational spectroscopies population and phase relaxation are often modeled by phenomenological level-dependent decay rates, that can be included in a perturbative treatment without major problems. 9,[60][61][62][63] However, these rates reflect the intermolecular dynamics in a rather indirect way, since they rely on the assumption of a white heat bath spectrum. Frequency fluctuations with a finite correlation time can be described by the stochastic model of Anderson and Kubo.…”

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confidence: 99%

“…49) Although the Fokker-Planck approach can be applied to any potential, we restrict ourselves in this pilot study to a harmonic coordinate, since different relaxation processes have been investigated for this system in great detail. 5,8,63,[67][68][69][70][71][72][84][85][86][87][88][89] It is then in principle possible to solve the integral for the potential kernel [eq. (8)] analytically: the first term on the r.h.s of eq.…”

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confidence: 99%

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Two-Dimensional Spectroscopy for Harmonic Vibrational Modes with Nonlinear System-Bath Interactions. I. Gaussian-White Case

Steffen

Tanimura

2000

J. Phys. Soc. Jpn.

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The quantum Fokker-Planck equation is derived for a system nonlinearly coupled to a harmonic oscillator bath. The system-bath interaction is assumed to be linear in the bath coordinates but quadratic in the system coordinate. The relaxation induced dynamics of a harmonic system are investigated by simulating the higher-order correlation functions of the Raman polarizability and the dipole moment, which represent the nonlinear optical responses of Raman or infrared spectroscopy. The 5th-order Raman response shows that, in addition to the frequency fluctuations induced by the bath, higher-order energy transfer between the system and bath plays a role. The nonlinearity of the system-bath interaction yields also an interesting feature in the 7th-order Raman echo or the 3rd-order infrared photon echo response: The calculations predict a finite signal for the case of a harmonic potential and a linear coordinate dependence of the polarizability or dipole while for linear system-bath coupling this response vanishes completely due to destructive interference of different Liouville space pathways.KEYWORDS: 2D Raman, 2D IR, quantum Fokker-Planck, nonlinear system-bath interaction monly assumes a certain functional form for the Hamiltonian of the medium, which allows for the derivation of closed form expressions that are fit to the experimental results. Such model approach, which is useful to understand the complex molecular interactions involved in optical processes, is complementary to more "realistic" approaches such as Molecular dynamics simulations. A typical example for this strategy is the Brownian oscillator model, which can be used to calculate, e.g., the first-order resonant IR response or the third-order offresonant Raman response. 5,8,9) Since the dipole moment or the polarizability is usually expanded in the power of molecular coordinate Q as μ(Q) = μ 1 Q + μ 2 Q 2 · · · or α(Q) = α 1 Q + α 2 Q 2 · · ·, the first-order IR or the third-order Raman onse in lowest order of Q is nothing but the two-time correlation functions of Brownian resp 3115 * E-mail: tanimura@ims.ac.jp rules for the transitions involved.To calculate the (non)linear optical response one com- §1. IntroductionFemtosecond nonlinear optical spectroscopies have proven to be valuable and versatile tools to obtain information on the dynamic characteristics of condensed phase systems.1-6) Usually, these experiments are described by a response function formalism, 5, 7) which is based on a perturbative expansion of the optical polarization in powers of the applied electric fields. For resonant spectroscopy, which is carried by the Infrared (IR) laser for molecular vibrational modes, the laser interaction is described by μE(t), where μ is the dipole moment of the system. Then, for example, the lowestorder signal is expressed by the dipole correlation function μ(t )μ(t) . For off-resonant Raman spectroscopy, in which resonance arises from a pair of laser pulses through Raman excitation processes, the laser interaction is described by αE 2 (t), where α is ...

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Section: )mentioning

confidence: 99%

Section: )mentioning

confidence: 99%

Two-Dimensional Spectroscopy for Harmonic Vibrational Modes with Nonlinear System-Bath Interactions. I. Gaussian-White Case

Steffen

Tanimura

2000

J. Phys. Soc. Jpn.

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“…The low-frequency Raman spectrum of benzene has been studied extensively in both the time and frequency domains through experiments 8,9,[13][14][15][16][17][18][19][20][21][22][23][24] and molecular simulations. 11,18,[25][26][27][28] McMorrow and Lotshaw observed the broad, flattened shape of the benzene OKE spectrum in 1993, and on a preliminary basis concluded that the spectral features are a result of collective modes arising from molecular aggregates.…”

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Assessing Polarizability Models for the Simulation of Low-Frequency Raman Spectra of Benzene

2014

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Optical Kerr effect (OKE) spectroscopy is a widely used technique for probing the low-frequency, Raman-active dynamics of liquids. Although molecular simulations are an attractive tool for assigning liquid degrees of freedom to OKE spectra, the accurate modeling of the OKE and the motions that contribute to it relies on the use of a realistic and computationally tractable molecular polarizability model. Here we explore how the OKE spectrum of liquid benzene, and the underlying dynamics that determines its shape, are affected by the polarizability model employed. We test a molecular polarizability model that uses a point anisotropic molecular polarizability and three other models that distribute the polarizability over the molecule. The simplest and most computationally efficient distributed polarizability model tested is found to be sufficient for the accurate simulation of the many-body polarizability dynamics of this liquid. We further find that the atomic-to-molecular polarizability transformation approximation [Hu et al. J. Phys. Chem. B 2008, 112, 7837-7849], used in conjunction with this distributed polarizability model, yields OKE spectra whose shapes differ negligibly from those calculated without this approximation, providing a substantial increase in computational efficiency.

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“…Second, the assumption that ⌸ ( j) (q) decreases quickly with increasing j may not be as valid for intermolecular modes as it is for intramolecular modes. 38 For instance, we have evidence from simulations that while the value of ⌸ (2) (Q) for an intramolecular mode can be accurately predicted given knowledge of ⌸ (1) (Q), no such relationship holds for intermolecular modes. 39 Thus, C 2,2 (x;tЈ) may make a significant contribution to C(x;tЈ) that cannot be predicted based on knowledge of C 1,1 (x;tЈ).…”

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confidence: 96%

“…37,38 There are two primary reasons why these other contributions may not be negligible. First, as is the case for intramolecular modes, there exist intermolecular modes whose symmetry dictates that ⌸ (1) (q)ϭ0 but for which ⌸ (2) (q) need not vanish.…”

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confidence: 99%

Polarization selectivity of nonresonant spectroscopies in isotropic media

Murry

Fourkas

1997

The Journal of Chemical Physics

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Articles you may be interested inWater models based on a single potential energy surface and different molecular degrees of freedomWe present an analysis of the contributions of the first-and second-derivative tensors of the many-body polarizability to third-and fifth-order nonresonant spectroscopies in isotropic media. Collision-induced effects are shown to have a notable influence on the second-derivative polarizability tensor (⌸ (2) ) for intermolecular modes. As a result, polarization selectivity in nonresonant intermolecular spectroscopies can be achieved in fifth-order spectroscopies. Additionally, terms in fifth-order spectroscopy that arise from three interactions through ⌸ (2) may not be negligible in many liquids. Our analysis shows that there exists no straightforward relationship between the observables in third-and fifth-order intermolecular spectroscopies. The predictions of this analysis are tested against the available experimental data for CS 2 .

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Level-dependent damping in intermolecular vibrations: Linear spectroscopy

Cited by 61 publications

References 59 publications

Two-Dimensional Spectroscopy for Harmonic Vibrational Modes with Nonlinear System-Bath Interactions. I. Gaussian-White Case

Two-Dimensional Spectroscopy for Harmonic Vibrational Modes with Nonlinear System-Bath Interactions. I. Gaussian-White Case

Assessing Polarizability Models for the Simulation of Low-Frequency Raman Spectra of Benzene

Polarization selectivity of nonresonant spectroscopies in isotropic media

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