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Field Dependent Electron and Quadrupole Spin Relaxation: A Unified Treatment

100%
Kruk D.
Acta Physica Polonica A
|
2007
|
vol. 111
|
issue 2
215-238
EN
This article reviews recent theoretical treatments of field dependent relaxation processes in complex systems containing mutually coupled dipolar, quadrupole, and electron spins. The presented approaches are based on an analogy between the Hamiltonian formalisms for quadrupole and zero field splitting interactions. Limitations of the presented treatments, resulting from the validity conditions of the second-order perturbation theory are discussed in detail.
2
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Influence of Sample Rotation on the Shape of the Free Induction Decay

63%
Blicharska B., Kruk D.
Acta Physica Polonica A
|
1993
|
vol. 84
|
issue 2
321-325
EN
Free induction decay is calculated at the presence of rotation of a liquid sample in a static magnetic field with a constant gradient.
3
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ESR Studies of Paramagnetic Centers in Pharmaceutical Materials - Cefaclor and Clarithromycin as an Example

45%
Skowronska A., Wojciechowski M., Ramos P., Pilawa B., Kruk D.
Acta Physica Polonica A
|
2012
|
vol. 121
|
issue 2
514-517
EN
Electron spin resonance (ESR) studies of two antibiotics, Cefaclor and Clarithromycin, have been performed in order to investigate concentration and dynamics of free radicals generated in these compounds due to thermal sterilization. For Cefaclor three combinations of temperature and heating time have been applied: 160°C, 170°C, 180°C for 120 min, 60 min, and 30 min, respectively, according to the pharmaceutical sterilization norm. Clarithromycin has been heated at 160°C for 120 min. The ESR lineshape has been investigated versus microwave power ranging from 2.2 mW to 70 mW. Electron spin-spin relaxation time has been estimated from the ESR lineshape analysis. Concentrations of radicals generated due to different sterilization procedures have been compared with the purpose to select the best sterilization scheme.
4
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NMR Relaxation and ESR Lineshape of Anisotropically Rotating Paramagnetic Molecules

45%
Kubica A., Milewska A., Noinska M., Earle K., Kruk D.
Acta Physica Polonica A
|
2012
|
vol. 121
|
issue 2
527-532
EN
The role of anisotropic rotation for electron spin resonance lineshape and nuclear magnetic relaxation dispersion profiles for paramagnetic molecules with electron spin quantum number S ≥ 1 is discussed. The ESR spectra and nuclear magnetic relaxation dispersion profiles are calculated by means of an approach based on the stochastic Liouville equation and referred to in the literature as "Swedish slow motion theory". This description is valid for arbitrary motional conditions and interaction strengths. Molecular tumbling influences the ESR spectra by modulating zero field splitting interactions. The nuclear spin relaxation is affected by the rotational motion in a twofold way: via the electron spin dynamics and as a direct source of modulations of the electron-nuclear dipole-dipole interactions. For coinciding principal axes systems of the permanent (residual, static) zero field splitting and rotational tensors the ESR lineshape is not affected by rotational anisotropy. Rotational anisotropy is important for nuclear relaxation as it is influenced by molecular rotation not only via the electron spin dynamics, but also directly by modulations of the electron spin-nuclear spin dipole-dipole interaction (when the dipole-dipole and zero field splitting frames do not coincide). The anisotropy effects depend strongly on the relative orientation of the dipole-dipole and permanent zero field splitting axes. Nevertheless, a different scenario is also possible. When the diffusion axis coincides with the dipole-dipole axis (but not with the principal axis system of the permanent zero field splitting), the nuclear spin relaxation as well as the ESR lineshape, become sensitive to the rotational anisotropy. The possible dependence of the ESR lineshape and nuclear spin relaxation on the rotational anisotropy should be carefully considered when attempting a joint analysis of ESR and nuclear magnetic relaxation dispersion results for paramagnetic molecules.
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