Nuclear Quadrupole Relaxation Research Articles

Apparent spin–spin relaxation time T*2 for an aged single crystal of p-dichlorobenzene using a superregenerative spectrometer

The nuclear quadrupole relaxation parameter T*2 has been measured for a single crystal of p-dichlorobenzene (α-phase) at 293 and 77 K using the detection threshold quench frequency shift technique and a superregenerative oscillator. The results are compared with those from polycrystalline samples.

Gamma-gamma angular correlation study of oxygen motion in yttria-stabilized zirconia

The nuclear quadrupole relaxation of 181Ta in ZrO 29 mole% Y 2O 3 has been measured by time differential angular correlations between 350 and 1150°C. The results are consistent with a distribution of the activation energy controlling the local motion of oxygen vacancies.

Nuclear quadrupolar spin-lattice relaxation in the amorphous state

It is proposed that the nuclear quadrupole spin-lattice relaxation in glasses is due to interaction of solitons with the nuclear quadrupole moment. The magnitude of the interaction is estimated and the resulting temperature dependence of the spin-lattice relaxation time is compared to experiment.

NQR resonance and relaxation in mixed crystals

The mechanism of the cubic to lower-symmetry phase transition occuring around 260 K in powders of mixed hexachlorostannates has been studied by nuclear quadrupole resonance and relaxation. Me propose a relation between the effects that the insertion of a NH + 4 impurity on a K + site has on the rigid reorientation rate of the octahedral SnCl 2− 6 ion on one hand, and on the phase transition temperature on the other hand.

A quantum-kinetic approach to the theory of nuclear quadrupole relaxation

A generalization of the approach to the magnetic resonance and relaxation problems based on the treating of the lattice as a classical system with random parameters is presented. The main point is taking into account the mutual influence of the spin system and the lattice motions more completely than it conventionally used to be done. The method developed is applied to the problem of the nuclear quadrupole relaxation due to the random rotations of nuclei with I= 3 2 in the case of the axially symmetric electric field gradient. The relaxation time temperature dependence is obtained in the temperature region where the Bayer theory is not valid.

Binding of coenzyme, coenzyme fragments, and inhibitors to native and carboxymethylated horse liver alcohol dehydrogenase from chlorine-35 nuclear magnetic resonance quadrupole relaxation

Binding of coenzyme, coenzyme fragments, and inhibitors to native and carboxymethylated horse liver alcohol dehydrogenase from chlorine-35 nuclear magnetic resonance quadrupole relaxation

Ion binding to cytochrome c studied by nuclear magnetic quadrupole relaxation

The enhancement of the 35Cl- transverse relaxation rate on binding of chloride ions to oxidized and reduced cytochrome c has been studied under conditions of variable sodium chloride concentration, temperature, pH, sodium phosphate, iron hexacyanide, and sodium cyanide concentration. The results revealed the presence of a strong binding site(s) for chloride in both oxidized and reduced cyt c, with a higher affinity in ferrocytochrome c. Competition experiments suggest that these sites also bind iron hexacyanide and phosphate. Cyanide binding to the iron in ferricytochrome c at alkaline and neutral pH was shown to decrease the binding of chloride. The pH dependence of the 35Cl- relaxation rate has been fitted by using literature pK values for ionizable groups. No indications of Na+ binding to oxidized and reduced cytochrome c have been observed by using 23Na+ NMR. Our results suggest that chloride is bound near the exposed heme edge and that the surface structure or dynamics in this region are different in the two oxidation states.

Nuclear quadrupole relaxation in solid Cu host doped with Rh

The nuclear quadrupole frequencies generated by 0.5 at% Rh in Cu host were measured by the TDPAC technique in the temperature range from 780 to 1040°C. At ∼900°C were observe strong damping of the TDPAC spectra, which is interpreted in terms of a relaxation mechanism.

Systematical trends of nuclear quadrupolar relaxation in metallic liquid alloys of indium

Applying the method of perturbed angular distributions following the nuclear reaction $^{115}\mathrm{In}(\ensuremath{\alpha},2n)^{117}\mathrm{Sb}^{m}$, systematic measurements have been made of the nuclear-quadrupolar relaxation rate ${R}_{Q}$ for $^{117}\mathrm{Sb}^{m}$ probe nuclei in liquid alloys of In, as a function of various parameters: the dependence of the rate enhancement on the partner element is established in 14 equicomposition alloys with $\mathrm{I}b$, $\mathrm{II}b$, $\mathrm{II}a$, $\mathrm{IV}a$, and $\mathrm{V}a$ group elements. The composition dependence of the rate in the In-rich domain has been recorded for ${\mathrm{In}}_{C}{X}_{1\ensuremath{-}C}$, $X=\mathrm{A}\mathrm{u},\phantom{\rule{0ex}{0ex}}\mathrm{H}\mathrm{g},\phantom{\rule{0ex}{0ex}}\mathrm{A}\mathrm{s},\phantom{\rule{0ex}{0ex}}\mathrm{a}\mathrm{n}\mathrm{d}\phantom{\rule{0ex}{0ex}}\mathrm{B}\mathrm{i}$, and the temperature dependence of the rate is presented for ${\mathrm{In}}_{0.5}$${\mathrm{Bi}}_{0.5}$ and ${\mathrm{In}}_{0.5}$${\mathrm{Hg}}_{0.5}$. On the average we find a correlation of the rate enhancement to the valence difference between In and the partner element. The composition dependence confirms the characteristic deviation from a simple substitutional behavior described by a $C(1\ensuremath{-}C)$ rule which has been found in earlier NMR work. The temperature dependence of the rate in ${\mathrm{In}}_{0.5}{X}_{0.5}$ alloys with enhancement, can be parametrized by an Arrhenius law where the activation energy is roughly a linear function of the alloy melting temperature; the proportionality factor, however, is about one half the factor occuring in diffusion. These results are examined in the frame of the Sholl and Warren theory for quadrupolar relaxation which we extend to alloys in its general form in terms of partial-dynamical structure factors taking advantage of analogies in the formulation of electrical resistivity. It is concluded from an evaluation of the formulas based upon a hard-sphere model that quadrupolar relaxation must be governed by the long-wavelength part of the structure factors. More specifically quadrupolar relaxation seems to be sensitive to the wave-number interval between the thermodynamical limit and the main peak of the static-pair correlation function of the liquid, a region which is poorly explored by other experimental techniques.

14N Nuclear Quadrupole Relaxation Near the Plastic Transition Point in the Low-temperature Phase of 1,4-Diazabicyclo[2.2.2]octane

Abstract The relaxation mechanism near the plastic transition in the low-temperature phase of 1,4-diazabicyclo[2.2.2]octane is attributed to the overall molecular tumbling. The activation energy is 23.0 kJ mol−1, which is nearly equal to the value of 22.2 kJ mol−1 in the proton NMR in the plastic phase.

Nuclear quadrupolar relaxation in molten salts

From the straightforward extension of a general theory for nuclear quadrupolar spin–lattice relaxation in monatomic liquids the rate RQ,α for an α ion in a simple uni-univalent ionic melt is expressed in terms of the local electric field gradients (e.f.g.) which originate from unlike or like charges external to the ion of interest, the van Hove time-dependent pair distribution function, and the static pair distribution function between unlike or like ions. RQ,α may be approximated in terms of the partial elastic limit Sγδ(k, 0) of the dynamic liquid structure factor and the partial weighting factor Iαγ, αδ(k) involving the e.f.g. contribution. For a sodium cation in molten NaCl the terms of INaγ,Naδ(k)(γ, δ; Na or Cl) are estimated under an assumption of an electrostatic quadrupolar interaction. These numerical values are 10–100 times greater than those of I(k) for liquid Ne calculated from exchange–van der Waals e.f.g. The experimental results of the partial static-structure factor Sγδ(k) and the static pair radial distribution function gNaγ(r)(γ; Na or Cl) for molten NaCl are of great consequence in calculations of both Sγδ(k, 0) and Iαγ,αδ(k). Numerical calculation of RO,Na for the sodium cation in the molten NaCl is in rough agreement with experiment. The relaxation process of 23Na in molten NaNO3 is caused by both translation and reorientational motions. The rotation-like motion gives rise to the time dependent e.f.g. at the Na nucleus and contributes mainly to the observed relaxation rate. Numerical calculations of the temperature dependence of RQ,Na in molten NaNO3 are in no good agreement with experiment.

Chloride ion binding to human plasma albumin from chlorine-35 quadrupole relaxation.

The 35Cl nuclear magnetic quadrupole relaxation enhancement on binding of chloride ions to human plasma albumin (HPA) has been studied under conditions of variable temperature, pH, ionic strength, protein, and sodium dodecyl sulfate concentration. A small number (less than 10) of chloride ions, most of which are bound to the primary detergent binding sites, contribute a major portion of the relaxation enhancement (greater than 80% at neutral pH). A comparison of the pH dependence of the relaxation rate with the hydrogen ion titration curve, which was determined and analyzed, identified ten lysyl and arginyl residues as being involved in the chloride ion binding. These data, in conjuction with NaDodSO4 titrations at different pH values and the amino acid sequence of HPA, suggests that the high-affinity chloride-binding sites are doubly cationic at neutral pH. An irreversible dimerization at acidic pH and 5 x 10(-5) m HPA was detected. The data also indicate the presence of internal modes of motion in the expanded forms of the HPA molecule, probably an independent reorientation of domains. The rate of exchange of chloride ions was shown to be much higher than the corresponding intrinsic relaxation rate in the temperature range 2--26 degrees C and pH values ranging from 4.0 to 10.5. No indications of protein-protein interaction could be found up to the physiological concentration of ca. 6 x 10(-4)m HPA at either neutral or alkaline pH. The mechanistic basis for HPA's exceptional capacity for binding of inorganic anions was discussed.

Concentration fluctuations in liquid alloys as seen by nuclear quadrupolar spin relaxation

A connection between thermodynamic data, concentration fluctuations at small wave numbers k and nuclear spin relaxation due to quadrupolar interaction in liquid binary metallic alloys is established by analysing experimental data on In 0.5X 0.5alloys.

Nuclear quadrupole relaxation in liquid metals and alloys

A mathematical formula for the quadrupole part of the nuclear spin relaxation rate in liquid metals is given. Preliminary calculations indicate that the formula may be capable of explaining the difference in variation with temperature of the rate in liquid metals and alloys.

N14NQR and relaxation at the ferroelectric transition in NaNO2

$^{14}\mathrm{N}$ nuclear quadrupole resonance and relaxation measurements in NaN${\mathrm{O}}_{2}$ around the ferroelectric transitions have been performed by pulse and Fourier-transform technique, with high-temperature resolution and accuracy. In the narrow temperature range in which the antiferroelectric phase exists and where previous authors failed to detect the nuclear-quadrupole-resonance (NQR) signals, the splitting of the ${\ensuremath{\nu}}_{+}$ and ${\ensuremath{\nu}}_{\ensuremath{-}}$ lines in two components were observed. A theory is developed to connect the NQR parameters to the torsional vibrations of the N${\mathrm{O}}_{2}^{\ensuremath{-}}$ ions as well as to the order-disorder reorientational fluctuations driving the transitions. The critical fluctuations are described through a kinematical Ising model. It is proven that the reorientational order-disorder variable is reversed by an angle which is not exactly $\ensuremath{\pi}$. By analyzing the experimental results in the light of the theoretical treatment interesting information on the critical dynamics is obtained.

Nuclear quadrupolar relaxation of Sb in liquid In-Sb alloys

In the In1-cSbc alloys the nuclear spin relaxation of Sb is measured using the TDPAD technique on the 340 mu s isomer 117mSb which is produced and aligned by the nuclear reaction 115In( alpha ,2n). The temperatures and compositions studied are: at T=900K, 0<or=c<or=0.8; at c=0, 430K<or=T<or=1000K; and at c=0.5, 770K<or=T<or=1100K. These measurements complement and extend existing NMR data for Sb in In1-cSbc. The quadrupolar contribution to the rate (TQ-1) is found to dominate for 117mSb. Its temperature dependence (at c=0.5) and concentration dependence (over the full range 0<or=c<or=1) can be described fairly well by the current theory of TQ-1 for a random substitutional metallic alloy. The parameters entering the theory are discussed. The quadrupole moment of the isomer 117mSb is determined as Q=(-)0.54(20) barn.

Calculation of nuclear quadrupolar relaxation in liquid metals

AbstractThe nuclear quadrupolar relaxation (NQR) rate W1q in liquid metals, in 69Ga, 115In and 201Hg is calculated by using the Warren theory. In order to do this, the experimental static interference function I(K) is considered and the dynamic interference function I(K, 0) is generated in the zero frequency limit. W1q is calculated in the temperature range 20 to 150 °C for 69Ga, 170 to 650 °C for 115In, and ‐‐‐35 to 80 °C for 201Hg. It is found that in all the three cases, the temperature dependence of the calculated W1q is in very good agreement with that of the experimenta W1q, but numerically the magnitudes of W1q for 115In and 201Hg deviate considerably from the experimental values. It is concluded that the antishielding factors used may be in error and that the present theory is superior to the earlier classical diffusion theory.

Nuclear Quadrupole Relaxation and Viscosity in Liquid Metals

AbstractIt is shown that the nuclear quadrupole relaxation rate due to the molecular motions in liquid metals is related to the shear and bulk viscosity and hence to the absorption coefficient of ultrasound. Application of the “extended liquid phonon” model of Ortoleva and Nelkin – which is the third of a series of continued‐fraction‐approximations for the van Hove neutron scattering function – gives a relation to the self diffusion constant. The predictions of the theory concerning the temperature dependence are compared with quadrupole relaxation measurements of Riegel et al. and Kerlin et al. in liquid gallium. Agreement is found only with the data of Riegel et al.

Temperature dependence of the nuclear quadrupole relaxation rates in liquid metals

Temperature dependence of the nuclear quadrupole relaxation rates in liquid metals

Nuclear quadrupolar spin-lattice relaxation in zinc-blende lattices by acoustic phonons

The nuclear quadrupolar spin-lattice relaxation by acoustic phonons in zinc-blende-type crystals is calculated for a general Raman process, in which pairs of phonons couple to the nucleus by an arbitrary type of mechanism. Over the temperature range of experimental interest ($T&gt;4.2$ K) it is shown that (i) regardless of the phonon-spin coupling mechanism, the quadrupolar relaxation rate has the form ${W}_{Q}=A{T}^{2}{E}_{A}(\frac{kT}{\ensuremath{\eta}\ensuremath{\hbar}{\ensuremath{\omega}}_{\mathrm{TA}}})$, where ${E}_{A}$ is a known function, and $A$ and $\ensuremath{\eta}$ are parameters which in principle can be calculated from a model for the interaction, but in practice are fitted to the data; (ii) the LA phonons contribute relatively little to the total relaxation, an amount which can vary by less than 3% of the total relaxation over the entire temperature range; (iii) relaxation is due predominately to phonons near the Brillouin-zone boundary; and (iv) phonons associated with various symmetry points on the Brillouin-zone boundary couple differently to the group-III than to the group-V nuclear sites.