Erratum: “Theory of damped quantum rotation in NMR spectra. I. Fundamental aspects” [J. Chem. Phys. 123, 204509 (2005)]

Ratajczyk, Tomasz; Szymański, Sławomir

doi:10.1063/1.4734318

Cited by 6 publications

(7 citation statements)

References 3 publications

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“…Its full exposition can be found in Refs. 15,16 , where the latter involves a general N-fold rotator.…”

Section: Overview Of Dqr Modelmentioning

confidence: 99%

“…15,16 These vibrational effects are described by the equation of motion for the density matrix of the rotator embedded in the phonon bath, derived using a variant of the Nakajima-Zwanzig theory. 29,30 A brief description of the essential properties of this crucial equation of motion is given in the Appendix.…”

Section: Overview Of Dqr Modelmentioning

confidence: 99%

“…9,13,14 However, the jump model has recently proved insufficient for exact description of NMR line shape effects in variabletemperature spectra of even very strongly hindered methyl groups. On the other hand, the competing, consistently quantum mechanical theory of damped quantum rotation (DQR)) 15,16 was shown to be adequate not only in low-temperature solids 17,18 but also in liquids above 170 K. [19][20][21][22] In place of the single classical rate constant characterizing the jump process, the DQR model employs two rate parameters. These are the rate constants of certain coherence-damping processes in the system of spinspace correlated torsional/rotational (TR) states of the methyl group treated as a hindered quantum rotator.…”

Section: Introductionmentioning

confidence: 99%

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A quantum mechanical alternative to the Arrhenius equation in the interpretation of proton spin–lattice relaxation data for the methyl groups in solids

Bernatowicz

Shkurenko

Osior

et al. 2015

Phys. Chem. Chem. Phys.

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CitationQuantum mechanical alternative to Arrhenius equation in the interpretation of proton spin-lattice relaxation data for the methyl groups in solids 2015 Phys. Chem. Chem. Phys. Theory of nuclear spin-lattice relaxation in methyl groups in solids has been a recurring problem in nuclear magnetic resonance (NMR) spectroscopy. The current view is that, except for extreme cases of low torsional barriers where special quantum effects are at stake, the relaxation behaviour of the nuclear spins in methyl groups is controlled by thermally activated classical jumps of the methyl group between its three orientations. The temperature effects on the relaxation rates can be modelled by Arrhenius behaviour of the correlation time of the jump process. The entire variety of relaxation effects in protonated methyl groups has recently been given a consistently quantum mechanical explanation not invoking the jump model regardless of the temperature range. It exploits the damped quantum rotation (DQR) theory originally developed to describe NMR line shape effects for hindered methyl groups. In the DQR model, the incoherent dynamics of the methyl group include two quantum rate, i.e., coherence-damping processes. For proton relaxation only one of these processes is relevant. In this paper, temperature-dependent proton spin-lattice relaxation data for the methyl groups in polycrystalline methyltriphenyl silane and methyltriphenyl germanium, both deuterated in aromatic positions, are reported and interpreted in terms of the DQR model. A comparison with the conventional approach exploiting the phenomenological Arrhenius equation is made. The present observations provide further indications that incoherent motions of molecular moieties in condensed phase can retain quantum character over much broader temperature range than is commonly thought. Eprint version

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“…Its full exposition can be found in Refs. 15,16 , where the latter involves a general N-fold rotator.…”

Section: Overview Of Dqr Modelmentioning

confidence: 99%

Section: Overview Of Dqr Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A quantum mechanical alternative to the Arrhenius equation in the interpretation of proton spin–lattice relaxation data for the methyl groups in solids

Bernatowicz

Shkurenko

Osior

et al. 2015

Phys. Chem. Chem. Phys.

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“…[20][21][22] It was later generalized to n-fold rotators. 23,24 A concise presentation of its version for threefold rotators was reported recently. 25 The eigenstates of a hindered methyl group, a prototypical threefold rotator, are delocalized over the three wells of the hindering potential.…”

Section: Theorymentioning

confidence: 99%

“…To assess the adopted assumption about a linear dependence of ∆ on temperature, the temperature behavior of k t was simulated theoretically using the already cited DQR model. 7,23,25 Formerly it afforded a perfect theoretical reproduction of the DQR effects evaluated from spectra of a single crystal 12 and of the spin-lattice relaxation data reinterpreted in the spirit of the DQR approach. 25,34 Before going into details of these calculations, a brief description of the relevant model parameters will be given.…”

Section: Interpretation Of the Obtained Dqr Parametersmentioning

confidence: 99%

Nonclassical dynamics of the methyl group in 1,1,1-triphenylethane. Evidence from powder 1H NMR spectra

Osior

Kalicki

Kamieński

et al. 2017

The Journal of Chemical Physics

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According to the damped quantum rotation (DQR) theory, hindered rotation of methyl groups, evidenced in nuclear magnetic resonance (NMR) line shapes, is a nonclassical process. It comprises a number of quantum-rate processes measured by two different quantum-rate constants. The classical jump model employing only one rate constant is reproduced if these quantum constants happen to be equal. The values of their ratio, or the nonclassicallity coefficient, determined hitherto from NMR spectra of single crystals and solutions range from about 1.20 to 1.30 in the latter case to above 5.0 in the former, with the value of 1 corresponding to the jump model. Presently, first systematic investigations of the DQR effects in wide-line NMR spectra of a powder sample are reported. For 1,1,1-triphenylethane deuterated in the aromatic positions, the relevant line-shape effects were monitored in the range 99-121 K. The values of the nonclassicality coefficient dropping from 2.7 to 1.7 were evaluated in line shape fits to the experimental powder spectra from the range 99-108 K. At these temperatures, the fits with the conventional line-shape model are visibly inferior to the DQR fits. Using a theoretical model reported earlier, a semiquantitative interpretation of the DQR parameters evaluated from the spectra is given. It is shown that the DQR effects as such can be detected in wide-line NMR spectra of powdered samples, which are relatively facile to measure. However, a fully quantitative picture of these effects can only be obtained from the much more demanding experiments on single crystals.

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Unusual effects in variable temperature powder NMR spectra of the methyl group protons in 9,10-dimethyltriptycene-d12

Bernatowicz

Ratajczyk

Kalicki

et al. 2014

Solid State Nuclear Magnetic Resonance

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Erratum: “Theory of damped quantum rotation in NMR spectra. I. Fundamental aspects” [J. Chem. Phys. 123, 204509 (2005)]

Cited by 6 publications

References 3 publications

A quantum mechanical alternative to the Arrhenius equation in the interpretation of proton spin–lattice relaxation data for the methyl groups in solids

A quantum mechanical alternative to the Arrhenius equation in the interpretation of proton spin–lattice relaxation data for the methyl groups in solids

Nonclassical dynamics of the methyl group in 1,1,1-triphenylethane. Evidence from powder 1H NMR spectra

Unusual effects in variable temperature powder NMR spectra of the methyl group protons in 9,10-dimethyltriptycene-d12

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