Selective determination of relaxation times in high resolution NMR

Freeman, Ray; Wittekoek, S.

doi:10.1016/0022-2364(69)90065-1

Cited by 88 publications

(45 citation statements)

References 31 publications

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“…The two couplings were then increased in magnitude until the undecoupled observed spectra matched the calculated spectra as closely as possible. Considering the uncertainties (f 0.5 s) in the assumed T2 values, the fact that the peaks need not have the same natural line-widths (14,15) and the inherent uncertainties in intensity measurements, it was concluded that 4~p H , N H 2 and 6 J, H , N H~ remained uncertain to within 0.03 Hz.…”

Section: Results and Discussion ( I ) Analyses Of Spectramentioning

confidence: 99%

Proton Magnetic Resonance Spectrum of 2-Chloroaniline-¹⁵N. Long-range Coupling Constants to Amino Protons from all Ring Protons

Wasylishen¹,

Schaefer²

1971

Can. J. Chem.

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The p.m.r. spectra of 2-chloroaniline and 2-chloroaniline-15N in benzene and toluene solutions are analyzed at 60 and 100 MHz under conditions where the amino protons are exchanging intermolecularly and also where they are not exchanging. The spectrum of 2-chloroaniline-H15ND in the absence of amino proton exchange is observed between -48 and 80 "C. In all situations fast rotation about the C-N bond evidently occurs. Long-range couplings of the amino protons to all ring protons are observed and their signs are determined. The nonplanarity of the amino group is discussed in terms of the longrange couplings, of the one-bond 15N-H couplings, and of the two-bond H-H couplings in the amino group. The signs and magnitudes of the coupling constants between the ring protons and 15N are also determined.Les spectres de r.m.p. des 2-chloroaniline et 2-chloroaniline 15N dans des solutions de benzene et toluene sont analysts a 60 et 100 MHz dans des conditions telles que l'echange intermolCculaire des protons de l'azote ait lieu, ainsi qu'en absence d'echange. Le spectre de la 2-chloroaniline-HL5ND en l'absence d'tchange est observe entre -48 et 80 "C. Dans tous les cas, la rotation rapide autour de la liaison G-N est mise en evidence. Les couplages a longue distance entre les protons de I'azote et tous les protons du cycle sont determines avec leurs signes. La non-planearite du groupement amine est discutee en termes de couplages a longue distance, de couplage I5N-N et de couplages H-H a travers deux liaisons dans le groupement amine. Le signe et la valeur des constantes de couplages entre les protons du cycle et le noyau 15N sont aussi determines.

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Section: Results and Discussion ( I ) Analyses Of Spectramentioning

confidence: 99%

Proton Magnetic Resonance Spectrum of 2-Chloroaniline-¹⁵N. Long-range Coupling Constants to Amino Protons from all Ring Protons

Wasylishen¹,

Schaefer²

1971

Can. J. Chem.

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“…For a mainly unperturbed situation, the proton H 1 could produce a relevant NOE on the proton These may also be detected by the determination of the cross-relaxation parameters σ ij for the proton pairs H 1 ϪH 4 and H 1 ϪH 2 . In the initial rate approximation, [15] these relaxation parameters describe the magnetization transfer between the spins i and j and depend on the internuclear distances r ij and on the rotational correlation times τ c of the vector ij, as described in Equation 2. (2) where γ is the proton magnetogyric ratio, ω 0 is the proton Larmor frequency and is the reduced Planck constant.…”

Section: Resultsmentioning

confidence: 99%

“…The data were zero-filled to 2 K ϫ 1 K and a Gaussian function was applied for processing in both dimensions. The selective relaxation rates were measured in the initialrate approximation [15] by employing a selective π pulse with the proton decoupler at the selected frequency for 25 ms. After the delay τ, a non-selective π/2 pulse was employed to detect the longitudinal magnetization. For the biselective measurements, the two protons were inverted consecutively.…”

Section: Methodsmentioning

confidence: 99%

NMR Detection of the Conformational Distortion Induced in Cyclodextrins by Introduction of Alkyl or Aromatic Substituents

et al. 2000

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“…The optimal pulse sequence in this case reduces to selectively inverting I z S ␤ to ϪI z S ␤ by weak rf irradiation at the frequency (ϪJ͞2) of the slowly relaxing multiplet component. Such selective inversions have been performed in the past for various applications, including the selective measurement of relaxation rates (11,(20)(21)(22)(23). Because the component I z S ␣ , which we do not want to invert, has a large transverse relaxation rate given by k a ϩ k c , it is possible to carry out the selective inversion process Selective population inversion of the energy levels ␣␤ and ␤␤, corresponding to a transfer of polarization I z (A) to longitudinal two-spin order 2I zSz (B).…”

Section: Theorymentioning

confidence: 99%

Boundary of quantum evolution under decoherence

Khaneja

Luy

Glaser

2003

Proc. Natl. Acad. Sci. U.S.A.

102

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Relaxation effects impose fundamental limitations on our ability to coherently control quantum mechanical phenomena. In this article, we use principles of optimal control theory to establish physical limits on how closely a quantum mechanical system can be steered to a desired target state in the presence of relaxation. In particular, we explicitly compute the maximum amplitude of coherence or polarization that can be transferred between coupled heteronuclear spins in large molecules at high magnetic fields in the presence of relaxation. Very general decoherence mechanisms that include cross-correlated relaxation have been included in our analysis. We give analytical characterization for the pulse sequences (control laws) that achieve these physical limits and provide supporting experimental evidence. Exploitation of crosscorrelation effects has recently led to the development of powerful methods in NMR spectroscopy to study very large biomolecules in solution. For two heteronuclear spins, we demonstrate with experiments that cross-correlated relaxation optimized pulse (CROP) sequences provide significant gains over the state-of-the-art methods. It is shown that despite large relaxation rates, coherence can be transferred between coupled spins without any loss in special cases where cross-correlated relaxation rates can be tuned to autocorrelated relaxation rates. T he control of quantum ensembles has many applications, ranging from coherent spectroscopy to quantum information processing. In practice, the quantum system of interest interacts with its environment, which leads to the phenomenon of relaxation. This results in signal loss and ultimately limits the range of applications. Relaxation is also a major road block standing in the way of practical quantum computing. Manipulating quantum systems in a manner that minimizes relaxation losses is a fundamental challenge of utmost practical importance. What is the ultimate limit on how close an ensemble of quantum systems can be steered from an initial state to a desired target state in the presence of relaxation? Until now there existed no theory that answers this question. This situation is comparable to the time before the fundamental efficiency limits of heat engines were known: More than 100 years after the invention of the steam engine, the physical limits for the maximum amount of work a steam engine could produce were unclear, despite decades of advances in its design. ''The theory of its operation is rudimentary and attempts to improve its performance are still made in an almost haphazard way'' (1). Of course, the maximum efficiency of a heat engine is not given by the cleverness of the engineer who attempts to build such a machine, but by the fundamental law of thermodynamics as captured in Carnot's Theorem.In this article we derive fundamental limits on how close an ensemble of nuclear spins can be driven from its initial state to a desired target state in the presence of relaxation. In particular, we derive the maximum efficiency of polarization and c...

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Selective determination of relaxation times in high resolution NMR

Cited by 88 publications

References 31 publications

Proton Magnetic Resonance Spectrum of 2-Chloroaniline-¹⁵N. Long-range Coupling Constants to Amino Protons from all Ring Protons

Proton Magnetic Resonance Spectrum of 2-Chloroaniline-¹⁵N. Long-range Coupling Constants to Amino Protons from all Ring Protons

NMR Detection of the Conformational Distortion Induced in Cyclodextrins by Introduction of Alkyl or Aromatic Substituents

Boundary of quantum evolution under decoherence

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Selective determination of relaxation times in high resolution NMR

Cited by 88 publications

References 31 publications

Proton Magnetic Resonance Spectrum of 2-Chloroaniline-15N. Long-range Coupling Constants to Amino Protons from all Ring Protons

Proton Magnetic Resonance Spectrum of 2-Chloroaniline-15N. Long-range Coupling Constants to Amino Protons from all Ring Protons

NMR Detection of the Conformational Distortion Induced in Cyclodextrins by Introduction of Alkyl or Aromatic Substituents

Boundary of quantum evolution under decoherence

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Proton Magnetic Resonance Spectrum of 2-Chloroaniline-¹⁵N. Long-range Coupling Constants to Amino Protons from all Ring Protons

Proton Magnetic Resonance Spectrum of 2-Chloroaniline-¹⁵N. Long-range Coupling Constants to Amino Protons from all Ring Protons