High-Resolution Rotation-Vibrational Raman Spectroscopy

Brodersen, Svend

doi:10.1007/978-3-642-81279-8_2

Cited by 24 publications

(10 citation statements)

References 100 publications

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“…Prior to each RCS experiment, the experimental apparatus function G ( t ) is measured via the zero time Kerr peak of Ar gas. The stimulated Raman response of the medium to the three laser pulses is described by the third-order susceptibility χ (3) ( t ), which can be modeled for t > 0 as where C is a proportionality constant and b J , K ,ν is an amplitude coefficient that includes the rotational and vibrational level population factors, the rotational ( g J , K ) and vibrational ( g ν ) degeneracies, nuclear spin statistics, and the rotational Raman intensity coefficients for anisotropic Raman scattering (Placzek–Teller factors). − The Δω J , K ,ν in eq are the frequencies of all rotational Raman-allowed transitions from states with rotational quantum numbers J , K and vibrational quantum number ν that can undergo stimulated Raman transitions within the femtosecond laser bandwidth of ∼100 cm –1 . While the classical bent and twist equilibrium geometries are asymmetric, the vibrational ν = 0 level is delocalized over all 20 stationary points (see Figure ), which renders cyclopentane an effective symmetric top molecule.…”

Section: Degenerate Four-wave Mixing Theory and Rcs Signal Analysismentioning

confidence: 99%

Probing the Structure, Pseudorotation, and Radial Vibrations of Cyclopentane by Femtosecond Rotational Raman Coherence Spectroscopy

et al. 2015

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The 10 nJ pulses from a Kerr-lens mode-locked Ti:sapphire oscillator (Mai Tai, SpectraPhysics) are amplified in a Ti:sapphire multipass chirped-pulse amplifier system (ODIN DQC, Quantronix), which is pumped by a 14 W pulsed frequency- The output of the fs laser system is reduced to a laser pulse energy between 75 − 120 µJ and split into three equally intense pump, dump and probe beams, which are aligned in a forward BOXCARS degenerate four-wave mixing (DFWM) arrangement, and focused by an f = 1000 mm achromatic lens into the center of either a 1.0 m long stainless-steel gas-cell or into the supersonic jet vacuum chamber. The probe beam runs over a retroreflector that is mounted on a high-precision 1000 mm long delay stage, housed in a vacuum tank with 800 nm AR coated windows that is evacuated to < 10 −3 mbar. The time-delay of the probe pulse is by measuring the retroreflector displacement with a two-axis He-Ne laser interferometric system (SP2000 D; SIOS GmbH) with an accuracy of ±30 nm. After the output window of gas-cell or jet vacuum chamber, the three input beams are blocked by a mask, while the DFWM signal beam is collimated, spatially filtered and detected by a thermoelectrically cooled GaAs photomultiplier (H7422-50, Hamamatsu). The signals are recorded with a 1 GHz/8-bit oscilloscope at a sweep rate of 8 GHz/s. The experiment is controlled and the data acquired by a PC using LabView.

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Section: Degenerate Four-wave Mixing Theory and Rcs Signal Analysismentioning

confidence: 99%

Probing the Structure, Pseudorotation, and Radial Vibrations of Cyclopentane by Femtosecond Rotational Raman Coherence Spectroscopy

et al. 2015

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“…60 For convenience, the g v,K,NS statistical weights are given for cyclohexane in Table 2 and for cyclohexane-d 12 in Table 3. For anisotropic Raman scattering, the rotational Raman intensity coefficients b J 0 K 0 JK are described with the ClebschÀGordan formalism 61 and are included according to Weber 62 for the O, P, R, and S transitions.…”

Section: Vibrational and Rotationalmentioning

confidence: 99%

Accurate Determination of the Structure of Cyclohexane by Femtosecond Rotational Coherence Spectroscopy and Ab Initio Calculations

et al. 2011

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We combine femtosecond time-resolved rotational coherence spectroscopy with high-level ab initio theory to obtain accurate structural information for the nonpolar molecules cyclohexane (C(6)H(12)) and cyclohexane-d(12) (C(6)D(12)). We measured the rotational B(0) and centrifugal distortion constants D(J), D(JK) of the v = 0 states of C(6)H(12) and C(6)D(12) to high accuracy, for example, B(0)(C(6)H(12)) = 4306.08(5) MHz, as well as B(v) for the vibrationally excited states ν(32), ν(6), ν(16) and ν(24) of C(6)H(12) and additionally ν(15) for C(6)D(12). To successfully reproduce the experimental RCS transient, the overtone and combination levels 2ν(32), 3ν(32), ν(32) + ν(6), and ν(32) + ν(16) had to be included in the RCS model calculations. The experimental rotational constants are compared to those obtained at the second-order Møller-Plesset (MP2) level. Combining the experimental and calculated rotational constants with the calculated equilibrium bond lengths and angles allows determination of accurate semiexperimental equilibrium structure parameters, for example, r(e)(C-C) = 1.526 ± 0.001 Å, r(e)(C-H(axial)) = 1.098 ± 0.001 Å, and r(e)(C-H(equatorial)) = 1.093 ± 0.001 Å. The equilibrium C-C bond length of C(6)H(12) is only 0.004 Å longer than that of ethane. The effect of ring strain due to the unfavorable gauche interactions is mainly manifested as small deviations from the C-C-C, C-C-H(axial), and C-C-H(equatorial) angles from the tetrahedral value.

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“…The nuclear spin states of cyclohexane are classified in the rigid-molecule point group D 3 d , and the combined statistical weights due to vibrational degeneracy, K -degeneracy, and nuclear spin g v , K ,NS are evaluated using the GAP software package and the irreducible representations Γ rve given by Weber; see Table 2 in ref . The b J ′ K ′ JK are the rotational Raman intensity coefficients for anisotropic scattering. , The rotational–vibrational populations p J , K , v = p J , K · p v are defined via independent rotational and vibrational temperatures T rot and T vib .…”

Section: Dfwm Theory and Data Analysismentioning

confidence: 99%

Femtosecond Rotational Raman Coherence Spectroscopy of Cyclohexane in a Pulsed Supersonic Jet

et al. 2011

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We combine the technique of femtosecond degenerate four-wave mixing (fs-DFWM) with a high repetition-rate pulsed supersonic jet source to obtain the rotational coherence spectrum (RCS) of cold cyclohexane (C(6)H(12)) with high signal/noise ratio. In the jet expansion, the near-parallel flow pattern combined with rapid translational cooling effectively eliminate dephasing collisions, giving near-constant RCS signal intensities over time delays up to 5 ns. The vibrational cooling in the jet eliminates the thermally populated vibrations that complicate the RCS coherences of cyclohexane at room temperature [Brügger, G.; et al. J. Phys. Chem. A 2011, 115, 9567]. The rotational cooling reduces the high-J rotational-state population, yielding the most accurate ground-state rotational constant to date, B(0) = 4305.859(9) MHz. Based on this B(0), a reanalysis of previous room-temperature gas-cell RCS measurements of cyclohexane gives improved vibration-rotation interaction constants for the ν(32), ν(6), ν(16), and ν(24) vibrational states. Combining the experimental B(0)(C(6)H(12)) with CCSD(T) calculations yields a very accurate semiexperimental equilibrium structure of the chair isomer of cyclohexane.

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High-Resolution Rotation-Vibrational Raman Spectroscopy

Cited by 24 publications

References 100 publications

Probing the Structure, Pseudorotation, and Radial Vibrations of Cyclopentane by Femtosecond Rotational Raman Coherence Spectroscopy

Probing the Structure, Pseudorotation, and Radial Vibrations of Cyclopentane by Femtosecond Rotational Raman Coherence Spectroscopy

Accurate Determination of the Structure of Cyclohexane by Femtosecond Rotational Coherence Spectroscopy and Ab Initio Calculations

Femtosecond Rotational Raman Coherence Spectroscopy of Cyclohexane in a Pulsed Supersonic Jet

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