Dephasing of Molecular Vibrations in Liquids

Oxtoby, David W.

doi:10.1002/9780470142592.ch1

Cited by 513 publications

(46 citation statements)

References 110 publications

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“…24 F I G U R E 5 Correlation between the mean value of the experimentally measured stretch band ( Figure 1A One possible reason for the decrease in the SR-IR intensity upon increasing the modifier concentration could be associated with the broadness of the band in the spectra. In addition to the distributions in bond parameters of the structural units (Figure 4), the broadness of the absorption (resonance) band could also be caused by nonirradiative energy dissipation processes; [83][84][85] if such inhomogeneous line broadening process exist, then the re-emission efficiency of the absorbed photon energy (which is defected as the reflectance) will decrease. Most silicate glasses with high concentrations of modifier ions have broader absorption bands and smaller k values than silica in the mid-IR region.…”

Section: Can the Si-o Stretch Bands In Ir Be Related To Bond Lengthmentioning

confidence: 99%

Searching for correlations between vibrational spectral features and structural parameters of silicate glass network

et al. 2020

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Infrared (IR) and Raman spectroscopic features of silicate glasses are often interpreted based on the analogy with those of smaller molecules, molecular clusters, or crystalline counterparts; this study tests the accuracy and validity of these widely cited peak assignment schemes by comparing vibrational spectral features with bond parameters of the glass network created by molecular dynamics (MD) simulations. A series of sodium silicate glasses with compositions of [Na2O]x[Al2O3]2[SiO2]98−x with x = 7, 12, 17, and 22 were synthesized and analyzed with IR and Raman. A silica glass substrate and a crystalline quartz were also analyzed for comparison. Glass structures with the same compositions were generated with MD simulations using three types of potentials: fixed partial charge pairwise (Teter), partial diffuse charge potential (MGFF), and bond order‐based charge transfer potential (ReaxFF). The comparison of simulated and experimental IR spectra showed that, among these three potentials tested, ReaxFF reproduces the concentration dependence of spectral features closest to the experimentally observed trend. Thus, the bond length and angle distributions as well as Si–Qn species and ring size distributions of silica and sodium silicate glasses were obtained from ReaxFF‐MD simulations and further compared with the peak assignment or deconvolution schemes—which have been widely used since 1970s and 1980s—(a) correlation between the IR peak position in the Si–O stretch region (1050‐1120 cm−1) and the Si–O–Si bond angle; (b) deconvolution of the Raman bands in the Si–O stretch region with the Qn speciation; and (c) assignment of the Raman bands in the 420‐600 cm−1 region to the bending modes of (SiO)n rings with different sizes (typically, n = 3‐6). The comparisons showed that none of these widely used methods is congruent with the bond parameters or structures of silicate glass networks produced via ReaxFF‐MD simulations. This finding invokes that the adequacy of these spectral interpretation methods must be questioned. Alternative interpretations are proposed, which are to be tested independently in future studies.

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Section: Can the Si-o Stretch Bands In Ir Be Related To Bond Lengthmentioning

confidence: 99%

Searching for correlations between vibrational spectral features and structural parameters of silicate glass network

et al. 2020

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“…In principle, all other superpositions of vibrational excitations (the so-called dark states) remain uncoupled. However, within this setting, a thermal bath of low-frequency rovibrational modes, which normally only introduces dephasing [14,15], interacts with the vibrational excitations and may influence the system dynamics.…”

Section: Introductionmentioning

confidence: 99%

Quantum theory of collective strong coupling of molecular vibrations with a microcavity mode

2015

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We develop a quantum mechanical formalism to treat the strong coupling between an electromagnetic mode and a vibrational excitation of an ensemble of organic molecules. By employing a Bloch-Redfield-Wangsness approach, we show that the influence of dephasing-type interactions, i.e., elastic collisions with a background bath of phonons, critically depends on the nature of the bath modes. In particular, for long-range phonons corresponding to a common bath, the dynamics of the 'bright state' (the collective superposition of molecular vibrations coupling to the cavity mode) is effectively decoupled from other system eigenstates. For the case of independent baths (or shortrange phonons), incoherent energy transfer occurs between the bright state and the uncoupled dark states. However, these processes are suppressed when the Rabi splitting is larger than the frequency range of the bath modes, as achieved in a recent experiment (Shalabney et al 2015 Nat. Commun. 6 5981). In both cases, the dynamics can thus be described through a single collective oscillator coupled to a photonic mode, making this system an ideal candidate to explore cavity optomechanics at room temperature. OPEN ACCESS RECEIVED

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“…In a disordered hydrogen-bond network, such as water, the v OH s0 to 1 transition frequency of the OH stretching mode depends on the local environment, resulting in a (inhomogeneous) frequency distribution within the OH stretching absorption band (left panel) (Rey et al, 2002). As the structure of the hydrogen bond network and -thus -the local molecular environments fluctuate, the frequency position of a particular oscillator changes with time, undergoing stochastic frequency shifts within the spectral envelope, i.e., spectral diffusion (Oxtoby, 1979). 2D absorption spectra (right panel of Figure 3B) reveal spectral diffusion directly: 2D spectra for Ts0 when the second and third pulses interact simultaneously with the sample reflect the initial frequency distribution.…”

Section: Probing Structural Dynamics In Real-time: Femtosecond Vibratmentioning

confidence: 99%

Ultrafast memory loss and relaxation processes in hydrogen-bonded systems

Elsaesser

2009

BCHM

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Structural memory of aqueous systems, such as neat water and biomolecules, in an aqueous environment is strongly influenced by hydrogen bond dynamics. Vibrational spectroscopy in the femtosecond (fs) time domain is applied to map structural dynamics in real-time and identify underlying molecular interactions. Neat liquid water displays an ultrafast loss of structural memory with the fastest decay of structural correlations occurring in the sub-100 fs regime. Both OH stretching and bending excitations of water molecules decay on a subpicosecond time scale, followed by dissipation of excess energy in the hydrogen bond network within a few picoseconds. Water shells around fully hydrated DNA show similar although slightly slower dynamics. A detailed study of hydration shells around ionic phosphate groups in the DNA backbone demonstrates a strong phosphate-water coupling and a subpicosecond rearrangement of hydrogen bonds upon energy disposal. Hydration shells serve as primary heat sinks for excess energy.

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Dephasing of Molecular Vibrations in Liquids

Cited by 513 publications

References 110 publications

Searching for correlations between vibrational spectral features and structural parameters of silicate glass network

Searching for correlations between vibrational spectral features and structural parameters of silicate glass network

Quantum theory of collective strong coupling of molecular vibrations with a microcavity mode

Ultrafast memory loss and relaxation processes in hydrogen-bonded systems

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