Raman Spectra in Organic Chemistry.

Hibben, James H.

doi:10.1021/cr60059a001

Cited by 30 publications

(13 citation statements)

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“…Weaker bands are also observed at about 420 and 550 cm –1 , mainly for detection on the red-detuned side of detection. The intense band at 885 cm –1 is again ascribed to a solvent contribution (EtOH) . Only very low power is observed for the high-frequency modes (note magnification) in the energetic region of 1000–2000 cm –1 , similar to that for ATR data.…”

Section: Resultssupporting

confidence: 64%

“…The intense band at 885 cm −1 is again ascribed to a solvent contribution (EtOH). 70 Only very low power is observed for the highfrequency modes (note magnification) in the energetic region RSB in EtOH. ATR transients were recorded at 18 800 cm −1 for T = 5 (black), 3 (red), 1 (blue), 0.5 (magenta), and 0.2 ps (green) and blocked IP (gray) using the cyan DFWM spectrum (Figure 3).…”

Section: ■ Resultsmentioning

confidence: 98%

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Excited State Vibrational Spectra of All-trans Retinal Derivatives in Solution Revealed By Pump-DFWM Experiments

2018

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The ultrafast structural changes during the photoinduced isomerization of the retinal-protonated Schiff base (RPSB) is still a poorly understood aspect in the retinal’s photochemistry. In this work, we apply pump-degenerate four-wave mixing (pump-DFWM) to all-trans retinal (ATR) and retinal Schiff bases (RSB) to resolve coherent high- and low-frequency vibrational signatures from excited electronic states. We show that the vibrational spectra of excited singlet states in these samples exhibit pronounced differences compared to the relaxed ground state. Pump-DFWM results indicate three major features for ATR and RSB. (i) Excited state vibrational spectra of ATR and RSB consist predominately of low-frequency modes in the energetic range 100–500 cm–1. (ii) Excited state vibrational spectra show distinct differences for excitation in specific regions of electronic transitions of excited state absorption and emission. (iii) Low-frequency modes in ATR and RSB are inducible during the entire lifetime of the excited electronic states. This latter effect points to a transient molecular structure that, following initial relaxation between different excited electronic states, does not change anymore over the lifetime of the finally populated excited electronic state.

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Section: Resultssupporting

confidence: 64%

Section: ■ Resultsmentioning

confidence: 98%

Excited State Vibrational Spectra of All-trans Retinal Derivatives in Solution Revealed By Pump-DFWM Experiments

2018

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“…Thus they are significantly more accurate than the corresponding absolute differential cross-sections, whose uncertainties are as significant as 24%. Calculated harmonic and VCI [3]+v depolarization ratios differ from the experimental data, on average, respectively, by 2.1% and 3.0%. These results indicate that the differences between calculated and measured absolute scattering cross-sections may originate, at least partially, from the significant experimental uncertainties accompanying measured Raman cross-sections.…”

Section: Computational Detailscontrasting

confidence: 53%

“…In this case, the integrals involving the operator b V Q ð Þ were evaluated using the tri-dimensional Gauss-Hermite quadrature, with 10 grid points for each dimension (N g = 10). The anharmonic Raman shifts obtained from the PJT1996 PES, presented in Table 1, are even more than those from the 3-mode representation computed at the CCSD(T)/FC/aug-cc-pVQZ level, for example, Δ % = 0.0 for the VCI [3] wave functions. In addition, the anharmonic scattering crosssections are now slightly closer to the experimental value.…”

Section: Computational Detailsmentioning

confidence: 85%

“…where I k and I ⊥ are the intensities of observed radiation with polarization directions parallel and perpendicular to the scattering plane. In Table 4 are listed the harmonic, VCI [3]+v and experimental values of ϱ fi for the totally symmetric fundamental transitions of water (λ 1 = 514.5 nm). Measured depolarization ratios have uncertainties of 1.5% or less.…”

Section: Computational Detailsmentioning

confidence: 99%

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Calculation of absolute Raman scattering cross‐sections using vibrational self‐consistent field/vibrational configuration interaction wave functions

Carvalho

Vidal

2022

J Comput Chem

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In the present study, the differential scattering cross-sections, depolarization ratios and Raman shifts of small molecular systems are obtained from configuration iteration wave functions of vibrational self-consistent field (VSCF) states. The transition polarizabilities were modeled using the Placzek approximation, neglecting those contributions not arising from the electric dipole mechanism. This theoretical approach is considered a good approximation for samples that absorb in the UV range if the excitation radiation falls in the visible region, as is the case of the molecules selected for the present study, namely: water, methane, and acetylene. Potential energy and electronic polarizability surfaces are calculated by the CCSD(T) and CC3 methods with aug-cc-p(C)V(T,Q,5)Z basis sets. The vibrational Hamiltonian includes the vibrational angular momentum contribution of the Watson kinetic energy operator. As expected, due to the variational nature of the VSCF and vibrational configuration interaction (VCI) methods, the Raman transition wavenumbers are substantially improved over the harmonic predictions. Surprisingly, the scattering cross-sections obtained using the harmonic approximation or the VSCF method better agrees with the experimental values than those cross-sections predicted using VCI wave functions. The more significant deviations of the VCI results from the experimental reference may be related to the significant uncertainties of the measured cross-sections. Still, it may also indicate that the VCI Raman transition moments may require a more accurate description of the electronic polarizability surface. Finally, the depolarization ratios calculated for H 2 O and C 2 D 2 using harmonic and VCI wave functions have similar accuracy, whereas, for C 2 H 2 and C 2 HD, the VCI results are more accurate.

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Properties and Reactions of Pyridine and its Hydrogenated Derivatives

Barnes

1960

Chemistry of Heterocyclic Compounds: A Series of Monographs

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Raman Spectra in Organic Chemistry.

Cited by 30 publications

References 0 publications

Excited State Vibrational Spectra of All-trans Retinal Derivatives in Solution Revealed By Pump-DFWM Experiments

Excited State Vibrational Spectra of All-trans Retinal Derivatives in Solution Revealed By Pump-DFWM Experiments

Calculation of absolute Raman scattering cross‐sections using vibrational self‐consistent field/vibrational configuration interaction wave functions

Properties and Reactions of Pyridine and its Hydrogenated Derivatives

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