• Journal of the Korean Magnetic Resonance Society
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• v.17 no.2
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• pp.86-91
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• 2013

Detailed information about the structural nature of three-coordinate borons in ${\beta}-BaB_2O_4$ is obtained through $^{11}B$ MAS NMR and $^{11}B$ single-crystal NMR. The three-coordinate $BO_3$ of the two borons B(1) and B(2) in ${\beta}-BaB_2O_4$ were distinguished. The spin-lattice relaxation time in the laboratory frame $T_1$ for B(1) and B(2) slowly decreases with increasing temperature, whereas the spin-lattice relaxation time in the rotating frame $T_{1{\rho}}$ for B(1) and B(2), which differs from $T_1$, is nearly constant. The B(1) and B(2) of the two types were distinguished by $^{11}B$ MAS NMR and $^{11}B$ single-crystal NMR.

• Bulletin of the Korean Chemical Society
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• v.20 no.10
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• pp.1205-1208
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• 1999

27Al NMR chemical shielding, quadrupolar coupling, and dipolar coupling interactions for corundum (α-Al2O3) are determined from the single-crystal 27 Al NMR spectra according to the rotation about three orthogonal axis. 27 Al NMR parameters obtained in this work with high accuracy are as follows: δiso = 7.4(4) ppm, QCC = 2.30(4) MHz, h = 0.08(3), and R = 2.0(3) kHz. This work appears to be the first NMR measurement of an aluminum-aluminum dipolar coupling interaction in α-Al2O3 crystals.

• Bulletin of the Korean Chemical Society
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• v.25 no.4
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• pp.529-532
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• 2004

Cesium-133 NMR spectra of a single crystal of tetragonal $Cs^+ (15-crown-5)_2I^-$ were obtained as a function of crystal orientation in an applied magnetic field of 9.40T and analyzed to provide the magnitudes and orientations of the $^{133}Cs$ chemical shift and quadrupolar tensors for two magnetically nonequivalent and symmetry related sites. Chemical shift tensor components and parameters of quadrupolar interactions are obtained as ${\delta}_{11}=46(1),\;{\delta}_{22}=60(1),\;{\delta}_{33}=-30(1)$ ppm, quadrupole coupling constant QCC = 581(1) kHz, and asymmetry parameter ${\eta}$ = 0.481(1), respectively. The nonaxially symmetric NMR parameters imply that the local environment of the cesium nuclei is nonaxially symmetric. The DANTE experiment burned holes in the $^{133}Cs$ NMR line of the title compound. The hole burning of the single crystal and powder $^{133}Cs$ NMR lines showed that the NMR lines are not homogeneously broadened.

• Journal of the Korean Magnetic Resonance Society
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• v.17 no.1
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• pp.19-23
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• 2013

The temperature dependences of the NMR spectrum and the spin-lattice relaxation times in $KH_2PO_4$ were investigated via single-crystal NMR and MAS NMR. The stretched-exponential relaxation that occurred because of the distribution of correlation times was indicative of the degree of the distribution of the double-well potential on the hydrogen bond. The behaviors responsible for the strong temperature dependences of the $^1H$ and $^{31}P$ spin-lattice relaxation times in the rotating frame $T_{1{\rho}}$ in $KH_2PO_4$ are likely related to the reorientational motion of the hydrogen-bond geometry and the $PO_4$ tetrahedral distortion.

• Journal of the Korean Magnetics Society
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• v.25 no.6
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• pp.185-188
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• 2015

We have investigated nuclear magnetic resonance of $^{23}Na$ nucleus in $NaMgCl_3$ single crystal in the temperature range 200 K~410 K using FT-NMR spectrometer. The spin-lattice relaxation times $T_1$ of $^{23}Na$ nucleus residing at cubic symmetry in the host crystal was measured as a function of temperature. The $T_1$ of $^{23}Na$ nucleus decreased with increasing temperature. The nuclear spin-lattice relaxation rate $1/T_1$ of $^{23}Na$ in $NaMgCl_3$ single crystal was proportional to the temperature T. This behavior is explained with the characteristic feature of the direct process between the nuclear spins and single phonon, $1/T_1$ being proportional to the absolute temperature. The activation energy calculated was $E_a=4.82J/mol$.

• Journal of the Korean Magnetic Resonance Society
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• v.21 no.2
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• pp.63-66
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• 2017

The $^{14}N$ NMR spectra for $(NH_4)_2SO_4$ crystals were obtained near the phase transition temperature $T_C=223K$, and were found to precisely reflect the symmetry change in the crystal at this first-order phase transition. Changes in the resonance frequencies near $T_C$ were attributed to the structural phase transition. In the ferroelectric and paraelectric phases, two inequivalent NH4 groups were distinguished in the $^{14}N$ NMR spectra. The two types, $NH_4$(1) and $NH_4$(2), have slightly different local environments. Consequently, we conclude that the phase transition is caused by the change in the environment of the $^{14}N$ nuclei in the $NH_4$ groups, rather than by the $SO_4$ groups.

• Journal of the Korean Magnetic Resonance Society
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• v.17 no.1
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• pp.24-29
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• 2013

The structural characteristics of 4-coordinate $BO_4$ [B(1)] and 3-coordinate $BO_3$ [B(2)] groups in $BiB_3O_6$ were studied by $^{11}B$ magic angle spinning (MAS) and single-crystal nuclear magnetic resonance (NMR) spectroscopy. The spin-lattice relaxation time in the laboratory frame, $T_1$, for $^{11}B$ decreased slowly with increasing temperature, whereas the spin-lattice relaxation times in the rotating frame, $T_{1{\rho}}$, for B(1) and B(2), which differed from $T_1$, were nearly constant. Further, $T_{1{\rho}}$ for B(1) and B(2) showed very similar trends, although the $T_{1{\rho}}$ value of B(2) was shorter than that of B(1). The 3-coordinate $BO_3$ and 4-coordinate $BO_4$ were distinguished by $^{11}B$ MAS NMR spectrum and $T_{1{\rho}}$.

• Journal of the Korean Magnetic Resonance Society
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• v.10 no.1
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• pp.1-37
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• 2006

General expressions for solid state NMR lines are described for transitions under static, magic angle spinning, and variable angle spinning conditions in the case where the principal axis system for the anisotropic chemical shift tensor is noncoincident with that of the quadrupole coupling tensor. It is demonstrated that solid state NMR powder pattern simulation program VMAS based on the conventional grid point method of integrating over the Euler angle space is fast enough in comparison with the POWDER simulation package and Gauss-point method.

• Journal of Magnetics
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• v.19 no.2
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• pp.116-120
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• 2014

The spin-lattice relaxation time, $T_1$, for $^{69}Ga$, $^{71}Ga$, and $^{75}As$ nuclei in GaAs:$Mn^{2+}$ single crystals was measured as a function of temperature. The values of $T_1$ for $^{69}Ga$, $^{71}Ga$, and $^{75}As$ nuclei were found to decrease with increasing temperature. The $T_1$ values in GaAs:$Mn^{2+}$ crystal are similar to those in pure GaAs crystal. The calculated activation energies for the $^{69}Ga$, $^{71}Ga$, and $^{75}As$ nuclei are 4.34, 4.07, and 3.99 kJ/mol. It turns out that the paramagnetic impurity effect of $Mn^{2+}$ ion doped in GaAs single crystal was not strong on the spin-lattice relaxation time.

• Journal of the Korean Chemical Society
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• v.54 no.6
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• pp.727-730
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• 2010

A tricyclic ring system bearing new stereogenic center namely 2,3-dihydro[1]benzothieno[3,2-b]pyrrole 4,4-dioxide was synthesized by asymmetric photoisomerization of 2,3-dihydropyrrolo[1,2-b]benzisothiazole 5,5-dioxide by irradiation with 245 nm emission of the low-pressure mercury lamp. The chemical structure and the purity of the photoproduct were delineated preliminarily by IR, NMR, and MS and finally confirmed by single crystal X-ray crystallography.