NMR OBSERVATION OF THE SPIN-LATTICE AND SPIN-SPIN RELAXATION IN SOME POLIBUTADIENES WITH DIFFERENT VINYL CONTENTS

2005 ◽  
Vol 19 (13) ◽  
pp. 2167-2174
Author(s):  
M. TODICA
Keyword(s):  
Relaxation Process ◽  
Spin Relaxation ◽  
Dynamic Properties ◽  
Dipolar Interaction ◽  
Transverse Magnetization ◽  
Spin Lattice ◽  
Polymeric Chains ◽  
Nmr Methods

Some polybutadienes with different vinyl contents were observed by NMR methods in order to disclose the influence of the microstructure of the polymeric chains on the relaxation of the longitudinal and transverse magnetization. The relaxation process is correlated with the dynamic properties of the polymeric chains. The residual dipolar interaction determined by the rigidity of the polymeric chains is observed by the pseudo-solid echo method and is associated with the vinyl contents of the samples.

COMPARATIVE OBSERVATION OF THE NMR SPIN-LATTICE AND SPIN-SPIN RELAXATION IN MOLTEN AND CROSS-LINKED POLIBUTADIENE

2005 ◽  
Vol 19 (10) ◽  
pp. 1771-1781 ◽  
Author(s):  
M. TODICA
Keyword(s):  
Spin Relaxation ◽  
Dipolar Interaction ◽  
Transverse Magnetization ◽  
Spin Lattice ◽  
Temporary Network ◽  
Polymeric Chains ◽  
Nmr Methods ◽  
Comparative Observation

The molten and cross-linked polybutadiene were observed by NMR methods in order to disclose the influence of the presence of the temporary and permanent junctions between the polymeric chains on the relaxation of the longitudinal and transverse magnetization. The residual dipolar interaction determined by the entanglements of the polymeric chains is observed by the pseudo-solid echo method and is associated with the existence of the temporary network.

A nuclear magnetic resonance study of pyridoxal phosphate – metal ion interactions. II. Binding of manganese(II)

1979 ◽  
Vol 57 (9) ◽  
pp. 1050-1055 ◽  
Author(s):  
Tenkasi S. Viswanathan ◽  
Terrence J. Swift
Keyword(s):  
Metal Ion ◽  
Pyridoxal Phosphate ◽  
Lattice Relaxation ◽  
Dipolar Interaction ◽  
Rotational Correlation Time ◽  
Nuclear Magnetic Resonance Study ◽  
Spin Lattice Relaxation ◽  
Relaxation Rates ◽  
Spin Lattice ◽  
Nmr Methods

The line width and spin–lattice relaxation rates of phosphorus and proton nuclei in PLP have been measured as a function of temperature in the presence of Mn(II) using pulsed nmr methods. The T1M of 31P in PLP-Mn(II) is very close to the T1M values of β- and γ-phosphorus atoms in ATP–Mn(II) at ∼40 °C. The T1 data of 31P and 1H have been interpreted in terms of the dipolar interaction between the electron and nuclear spins. With the assumption that the Mn(II) interacts directly with the phosphate of PLP the rotational correlation time τc at 38 °C was calculated to be 7.6 × 10−10 s from phosphorus T1 data. This τc value was subsequently used to calculate metal–proton distances from proton T1 and T2 data. The results lead to the conclusion that the phosphate-bound metal interacts directly with the aldehyde oxygen in a 1:1 PLP–Mn(II) complex. The linewidth of the 13C resonances of PLP in the presence of Mn(II) supports this conclusion. The structure assigned for PLP–Mn(II) complex is in conformity with the structure for PLP-Co(II) complex.

OBSERVATION OF THE NMR SPIN–SPIN RELAXATION OF SOME POLYBUTADIENE-C7D8 SOLUTIONS

2006 ◽  
Vol 20 (28) ◽  
pp. 1795-1801
Author(s):  
M. TODICA
Keyword(s):  
Temperature Dependence ◽  
Spin Relaxation ◽  
Experimental Parameter ◽  
Nmr Relaxation ◽  
Transverse Magnetization ◽  
Large Temperature ◽  
Linear Temperature Dependence ◽  
Linear Temperature ◽  
Polymeric Chains ◽  
Relaxation Curves

The NMR relaxation of the transverse magnetization of the protons attached to the polymeric chains was observed for the molten polybutadiene and for some polybutadiene–toluene solutions in a large temperature domain. The superposition properties of the relaxation curves, the linear temperature dependence of the experimental parameter t0.6(T) and the observation of the pseudo-solid echoes were correlated to the existence of the temporary junctions between the polymeric chains.

Electron Spin Relaxation of (Diphenyl) in Dimethoxyethane

1975 ◽  
Vol 30 (6-7) ◽  
pp. 883-890 ◽  
Author(s):  
F. Köksal ◽  
G. J. Krüger
Keyword(s):  
Spin Relaxation ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Dipolar Interaction ◽  
Translational Diffusion ◽  
Spin Lattice Relaxation ◽  
High Concentration ◽  
Electron Spin Relaxation ◽  
Spin Lattice ◽  
Electron Relaxation

Abstract The electron relaxation times T1 and T2 have been measured by ESR pulse techniques in solutions of normal and perdeuterated (diphenyl)- in dimethoxyethane at various radical concentrations and temperatures. The results are discussed in terms of different relaxation mechanisms. The most important contribution to spin-lattice relaxation at high concentration is dipolar interaction with other radical electrons modulated by translational diffusion. Spin-spin relaxation has in addition contributions from electron exchange and ion pairing.

Nuclear spin-lattice relaxation in a multi-spin system. A spin 1/2 particle dipolar coupled to a spin 1 and spin 3/2 particle. 13C spin relaxation in urea

1980 ◽  
Vol 33 (12) ◽  
pp. 2571
Author(s):  
DM Doddrell ◽  
KM Kleinschmidt
Keyword(s):  
Spin Relaxation ◽  
Matrix Theory ◽  
Relaxation Times ◽  
Coupled System ◽  
Lattice Relaxation ◽  
Dipolar Interaction ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
System A ◽  
Density Matrix Theory

Density matrix theory is used to show that for S = 1/2, 1, 3/2 the decay of the I-magnetization (I = 4) in a two-spin IS dipolar coupled system is governed by the differential equation ��������������� d<Iz>/dt= -k1{J(ωI-ωS)+3J(ωI)+6J(ωI+ωS)}{<Iz>-I0}������ ������������������-k2{6J(ωI+ωS)-J(ωI-ωS)}{<SZ>-S0} where k1 and k2 are positive constants dependent on S and the dipolar interaction constants. It follows that if <S2> = 0, as arises on S- irradiation, or <SZ> = S0, as in paramagnetic transition-metal complexes, the decay of the I-magnetization is exponential.�The theory is used to analyse 14N,2H dipolar-induced 13C spin relaxation in deuterated urea. It is shown that at low temperatures dipolar interactions dominate the relaxation whereas at high temperatures spin rotation effects become important. The relaxation times are very long; at 300 T1 is 114s.

Protonenspin-Relaxation durch Spinrotationswechselwirkung in kristallinen Methylnaphthalinen/Proton Spin-Lattice Relaxation on Crystalline Methylnaphthalenes by Spin-Rotational Interaction

1975 ◽  
Vol 30 (10) ◽  
pp. 1302-1307 ◽  
Author(s):  
J. U. von Schütz
Keyword(s):  
Spin Relaxation ◽  
Lattice Relaxation ◽  
Dipolar Interaction ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Field Range ◽  
Spin Lattice ◽  
Methyl Naphthalene ◽  
First Time ◽  
Rotational Interaction

Abstract The high temperature behavior of the longitudinal proton spin relaxation time T1 of several methyl naphthalene crystals, differing in the arrangement and number of the substituted CH3-groups, was investigated in a large magnetic field range. It could be prooved - for the first time via proton spin relaxation - that in solids the fast reorientation of CH3-groups with low hindering barriers can lead to remarkable contributions to the total relaxation rate by spin-rotational interaction, in addition to the well known dipolar interaction discussed in preceeding works.

Photophysics of the lowest triplet state in 2-benzoylpyridine crystals. II. Optically detected e. p. r. in zero and high magnetic fields

1979 ◽  
Vol 369 (1737) ◽  
pp. 187-206 ◽  
Keyword(s):  
Triplet State ◽  
Rate Constants ◽  
Radiative Decay ◽  
Dynamic Properties ◽  
Deep Trap ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Zero Field ◽  
Spin Lattice ◽  
Optically Detected

Optically detected zero-field resonance has been used to characterize the intrinsic and deep trap 3 nπ * states in single crystals of 2-benzoylpyridine at 4.2 K. The dynamic properties of these states were studied by means of time-resolved modulated phosphorescence (t. r. m. p.) and estimates for the rate constants for depopulation and spin-lattice relaxation of the magnetic sub-levels obtained by computer simulation. For all species, depopulation from ז z dominates, having rates of order 100 s -1 , but the ז x and ז y sub-states have substantial radiative activity. The orientations of the fine-structure tensors of the magnetic species were determined from high-field e. p. r. spectra. Assuming that z is parallel to C = O, excitation causes the C = O direction to change by 8 ± 2° for the intrinsic species and by an in-significant amount for the deep trap. These spectra also demonstrated that the intrinsic triplet state is mobile. This species is believed to be a polaron with slow intersite hopping rate. A maximum energy transfer rate of 10 4 -10 5 s -1 was found for transfer between translationally inequivalent sites symmetry-related by twofold rotation about the crystal b -axis. Rate estimates for transfer to the other two translationally inequivalent sites established the two dimensional nature of the polaron. The sign and shape of the zero-field resonances for the intrinsic species were found to depend on whether excitation was through S 1 or T 1 . From the parameters required to simulate the corresponding t. r. m. p. signals it is inferred that the changes are largely due to differences in the rate constants for non-radiative decay. The deep trap was shown to have an orientation and magnetic properties similar to those of the intrinsic species, and is believed to be a physical defect. It has radiative activity from the ז x sub-level which is significantly less than for the intrinsic species. Spin-lattice relaxation is fast for the mobile intrinsic species ( ca . 10 4 s -1 ) compared with the deep trap rate ( ca . 50 4 s -1 ). For the intrinsic species a field dependence for spin-lattice relaxation is apparent.

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