Values Of Quadrupole Coupling Constants Research Articles

Microwave measurements of rotational transitions and nitrogen quadrupole coupling for 2-aminopyridine

The high-resolution microwave rotational spectrum was measured for 2-aminopyridine in the 4.5–13.2 GHz range using a pulsed beam Fourier transform microwave spectrometer. The measured transitions for the parent isotopologue in the 0+ vibrational state of the amino group inversion vibration were used to determine accurate rotational constants and quadrupole coupling constants for the two 14N atoms in the molecule. The molecular parameters determined for the 2-aminopyridine in 0+ vibrational state have the following values: A = 5780.374(1) MHz, B = 2733.5017(3) MHz, C = 1857.6768(3) MHz, 1.5χaa (14N1) = 3.5789(45) MHz, 0.25(χbb – χcc) (14N1) = 1.5033(24)MHz, 1.5χaa (14N2) = -0.0958(70) MHz, and 0.25(χbb – χcc) (14N2) = −1.1615(21) MHz. The measured quadrupole coupling constants are in excellent agreement with those calculated using different computational methods and basis sets. It is noted that the calculation using the MP2 functional with cc-pvDz basis set closely reproduces the experimental values for quadrupole coupling constants for the two 14N atoms.

Theoretical studies of cubic AuCu3-type intermetallic actinide compounds NpPx3 (Px=Al, Ga, In)

In this paper, we explore the structural, magnetic, electronic specific heat, electric field gradient (EFG) as well as quadrupole coupling constant of NpPx3 (Px = Al, Ga, In) by using LDA, GGA, GGA + U and HF-PBEsol. The relativistic effects of electrons of the actinides are considered by spin-orbit coupling calculations. The comparison of the calculated structural parameters, magnetic moments and EFG of these materials satisfy the available experimental results. This consistency shows the effectiveness of our theoretical tools. The calculated EFG and quadrupole coupling constant value increase in NpPx3 from Al to In due to change of fermions. The EFG and quadrupole coupling constant in NpPx3 (Px = Al, Ga, In) is mainly originated from f-f and p-p contributions of Np atom and p-p contribution of Al, Ga and In atom.

Tuning of tetrel bonds interactions by substitution and cooperative effects in XH3Si···NCH···HM (X = H, F, Cl, Br; M = Li, Na, BeH and MgH) complexes

ABSTRACTIn this work, the interplay between the tetrel bond and the dihydrogen bond is investigated in ternary XH3Si···NCH···HM complexes, where X = H, F, Cl, Br and M = Li, Na, BeH, MgH. The nature of Si···N and H···H interactions is studied by molecular electrostatic potential (MEP), noncovalent interaction and electron localisation function analyses. All binding distances in the ternary complexes are shorter than those of isolated XH3Si···NCH and NCH···HM systems. That is, the two types of interactions have a cooperative effect on each other. The results of the MEP analysis indicate that the enhancement of the Si···N and H···H bonds can mainly be attributed to the electrostatic interaction. The plot of the reduced density gradient versus sign (λ2)ρ indicates that the location of the spike associated with each interaction in the ternary systems moves slightly towards the negative (λ2)ρ values with respect to the binary systems. This confirms that both Si···N and H···H interactions in the ternary complexes are strengthened by the presence of other. Besides, cooperative effects lead to a considerable change in the 14N nuclear quadrupole coupling constant values of the ternary complexes relative to the XH3Si···NCH complexes.

Molecular motion of alcohols adsorbed in ACF hydrophobic nanoslits as studied by solid-state NMR

The molecular motion and local structure of methanol-d1 (CH3OD) and ethanol-d1 (C2H5OD) in activated carbon fiber (ACF) with a slit width of 0.7 and 1.1 nm have been investigated by solid-state 1H and 2H NMR. 2H NMR spectra for alcohols confined in ACF gave a so-called Pake doublet below 140 K, which were characterized by the 2H quadrupole coupling constant (QCC) of 185 kHz and the asymmetric parameter of the electric-field-gradient tensor (η) of 0.1. The QCC value of the deuteron was indicative of the hydrogen bond formation with the O···O distance of ca. 0.27 nm, suggesting the solid-like feature of alcohols in ACFs. The quadrupole broadening vanished on heating and the single isotropic resonance line was observed. Alcohol molecules were undergoing a rapid motion like as in the bulk liquid, indicating a transition from solid to liquid in ACFs. Temperature-dependent 1H NMR spectra were used for evaluating the Ea value for reorientation in solid-like alcohols, whereas the 2H NMR spectra were used for obtaining the translation accompanying reorientation in liquid-like alcohols. Alcohols with a bilayered structure in ACF with a slit width of 1.1 nm gave similar Ea values, whereas C2H5OD in ACF with a slit width of 0.7 nm, in which a monolayered structure is expected, exhibited a cross-over of two activation processes at 172 K. The variation in Ea was probably caused by the structural relaxation concerning with the hydrogen bonding formation and/or excitation of the large amplitude local motion. The competition of the directionality of hydrogen bonds and a freedom of molecular orientation plays an important role to characterize the intermolecular structure as well as the physicochemical properties in amphipathic molecules in confinement.

Interplay Between Lithium Bonding and Halogen Bonding in F3CX•••YLi•••NCCN and F3CX•••NCCN•••LiY Complexes (X = Cl, Br; Y = CN, NC)

MP2 calculations with cc-pVTZ basis set were used to analyze intermolecular interactions in F3CX···YLi···NCCN and F3CX···NCCN···LiY triads (X = Cl, Br; Y = CN, NC) which are connected via halogen and lithium bonds. Those complexes with the role of LiY as halogen acceptor and lithium donor show cooperativity with energy values ranging between -1.97 and -2.92 kJ mol -1 . Those complexes with simultaneous role of NCCN as halogen and lithium acceptor are diminutive with energetic effects between 1.24 and 1.86 kJ mol -1 . Results of energy decomposition analysis revealed that the electrostatic interactions are the major source of the attraction in the title complexes. The nuclear quadrupole coupling constant values at the sites of halogen atoms can be regarded as good descriptors to quantify the degree of cooperative/diminutive effects in the title systems.

Water confinement in faujasite cages: a deuteron NMR investigation in a wide temperature range. 1. Low temperature spectra.

Deuteron NMR spectra were measured for D2O confined in NaX, NaY, and DY faujasites with various D2O loadings at temperatures ranging from T = 70 K to T = 200 K with the aim to study the molecular mobility of confined water as a function of Si/Al ratio and loading. The recorded spectra were fitted with linear combinations of representative spectral components. At low loading, with the number of water molecules per unit cell close to the abundance of sodium cations, a component related to π-jumps of water deuterons about the 2-fold symmetry axis dominated. For loadings at levels 3 times and 5 times higher than the initial loading level, Pake dublets due to rigid water deuterons dominated the recorded spectra. A set of the quadrupole coupling constant values of localized water deuterons was derived from the analysis of the Pake dublets. Their values were attributed to deuteron positions corresponding to the locations at oxygen atoms in the faujasite framework and locations within hydrogen-bonded water clusters inside faujasite cages. The contributions of the different spectral components were observed to change with increasing temperature according to the Arrhenius law with a characteristic dynamic crossover point at T = 165 K. Below T = 165 K a spectral component was observed whose contribution changed with temperature, yielding the activation energy of about 2 kJ/mol, characteristic for jumps between inversion-related water positions in clusters.

Density functional theory study of nitrogen-14 nuclear quadrupole coupling parameters of L-histidine: hydrogen-bonded system

The calculations of nitrogen-14 nuclear quadrupole parameters, nuclear quadrupole coupling constant, χ, and asymmetry parameter, η, of L-His were done in two distinct environments: one as a free fully optimized molecule, an isolated molecule with the geometrical parameters taken from X-ray, and the other in the orthorhombic and monoclinic solid states. The most probable interacting molecules with the central molecule in the crystalline phase were considered in the hexameric clusters to include hydrogen-bonding effects in the calculations. The computations were performed with PW91P86/6-31++G** and B3LYP6-31++G** methods using the Gaussian 98 program. The good agreement between the nitrogen-14 quadrupole parameters of the free His and imidazole molecules with their microwave available data demonstrates that the applied level of theory and the 6-31++G** basis set are suitable to obtain reliable electric field gradient values. In the solid state, the shifts of quadrupole coupling parameters from the monomer to the solid phase are reasonably well reproduced for the amino and imino sites of imidazole ring in a hexameric cluster. That implies the fact that the hexameric cluster worked effectively to generate the results which are compatible with the experiment. The quadrupole coupling constant values of -N(+) H(3) group are in fair agreement with the experiment. This discrepancy is due to the absences of vibrational effects and the rotation of -N(+) H(3) group around N-C(α) bond.

A solid-state 35/37Cl NMR study of a chloride ion receptor and a GIPAW-DFT study of chlorine NMR interaction tensors in organic hydrochlorides

The results of a 35/37Cl solid-state nuclear magnetic resonance (SSNMR) study of the 1-butyl-3-methylimidazolium chloride complex of meso-octamethylcalix[4]pyrrole (1) are reported. Line shapes obtained from magic-angle-spinning and stationary powder samples collected at 9.4 and 21.1 T are analyzed to provide the 35/37Cl quadrupolar tensor and chemical shift (CS) tensor and their relative orientation. The relatively high symmetry of the chloride ion coordination environment is manifested in the small value of the quadrupole coupling constant, CQ(35Cl) = 1.0 MHz. The isotropic chemical shift of 120 ppm (with respect to NaCl(s)) is at the upper edge of the typical range seen for organic hydrochlorides. Consideration of chemical shift anisotropy (span, Ω = 50 ppm) and non-coincidence of the quadrupolar and CS tensors were essential to properly simulate the experimental spectra. The utility of gauge-including projector-augmented wave density functional theory (GIPAW-DFT) calculations of chlorine quadrupolar and CS tensors in organic chlorides was explored by validation against available benchmark experimental data for solid amino acid hydrochlorides. The calculations are shown to systematically overestimate the value of the 35Cl quadrupole coupling constant. Additional calculations on various hydrated and solvated models of 1 are consistent with a structure in which solvent and water of hydration are absent.

COMPUTATIONAL STUDY OF A CNT-URACIL-CNT COMPOUND

Density functional calculations were performed to investigate the properties of a combination of two representative carbon nanotubes by assistance of the atomic sites of uracil, which is the characteristic nucleobase of RNA. The obtained parameters indicated that the resulting compound exhibit new properties with respect to the original nanotubes and uracil. The effects of the modification process were significant for the dipole moments and conductivity properties of the components as were seen by the significant changes in the new compound. The values of quadrupole coupling constants for the nitrogen and oxygen atoms of the uracil counterpart of the investigated models also indicated the effects of changes of the electronic environments of the components due to the modification process.

Computational studies on boron nitride and boron phosphide nanotubes: Density functional calculations of boron-11 electric field gradient tensors

We have performed density functional theory (DFT) calculations employing BLYP exchange functional and 6–31 G * standard basis set by GAUSSIAN 98 package of program. The electronic structure properties of representative zigzag and armchair models of boron nitride nanotube (BNNT) and boron phosphide nanotube (BPNT) have been studied. The (6,0) and (4,4) structures have been optimized and the electric field gradient (EFG) tensors have been calculated at the sites of various boron-11 nuclei. The calculated EFG tensors have been converted to the equivalent experimental nuclear quadrupole resonance (NQR) parameters, quadrupole coupling constant and asymmetry parameter. The results revealed that the boron atoms at the edges of nanotubes play dominant roles in determining the electronic behaviors of BNNT and BPNT. The average of the calculated values of quadrupole coupling constants at the sites of boron-11 nuclei is in good agreement with experiments.

129I Mössbauer Spectroscopic Study of a Metallic MMX Chain System

One-dimensional iodide-bridged mixed-valence binuclear platinum complexes (the so-called "MMX chains") and their Pt(III) dimer precursors were investigated with (129)I Mossbauer spectroscopy. Spectra consisting of two sets of octuplets were observed at low temperatures for a neutral MMX chain complex, Pt(2)(dtp)(4)I (dtp = C(2)H(5)CS(2)(-)), with various charge-ordering states at the Pt dimers, indicating that the charge-ordering state is in an alternate-charge-polarization phase (ACP: ...[Pt(2+)-Pt(3+)]-I(0.4-)-[Pt(3+)-Pt(2+)]...I(0.3-)...), which is consistent with a previous low-temperature X-ray diffraction study. The estimated valence states of the bridging iodines of [(C(2)H(5))(2)NH(2)](4)[Pt(2)(pop)(4)I] (pop = H(2)P(2)O(5)(2-)), with a charge-polarization phase (CP: ...[Pt(2+)-Pt(3+)]-I(0.4-)...[Pt(2+)-Pt(3+)]-I(0.4-)...), and [H(3)N(CH(2))(6)NH(3)](2)[Pt(2)(pop)(4)I], with a charge-density-wave phase (CDW: ...[Pt(2+)-Pt(2+)]...I(0.3-)-[Pt(3+)-Pt(3+)]-I(0.3-)...), suggest that the covalent bond interaction is dominant in the CDW phase, whereas the Coulomb interaction is dominant in the CP phase. The estimated absolute quadrupole coupling constant (QCC) values for negatively charged MMX chain complexes with pop ligands are larger than those for neutral MMX chain complexes with CH(3)CS(2)(-) (dta) ligands, implying that the Madelung potential formed by the more-negative pop ligands and countercations effectively contributes to the physical properties of the pop system. The three Pt(III) dimer complexes Pt(2)(dta)(4)I(2), Pt(2)(dtp)(4)I(2), and K(4)[Pt(2)(pop)(4)I(2)] showed almost the same isomer shifts, indicating that the valence state of the iodide ion (I(0.5-)) depends negligibly on the terminal ligand. The QCC value observed for K(4)[Pt(2)(pop)(4)I(2)] was larger than those for Pt(2)(dta)(4)I(2) and Pt(2)(dtp)(4)I(2), originating from the anisotropic arrangement of the iodide anions, which form layers lying on the ab plane in the crystal.

Dynamics of Dilute Water in Carbon Tetrachloride

A dilute solution of water in a hydrophobic solvent, such as carbon tetrachloride (CCl4), presents an opportunity to study the rotational properties of water without the complicating effects of hydrogen bonds. We report here the results of theoretical, experimental, and semiempirical studies of a 0.03 mole percent solution of water in CCl4. It is shown that for this solution there are negligible water-water interactions or water-CCl4 interactions; theoretical and experimental values for proton NMR chemical shifts (deltaH) are used to confirm the minimal interactions between water and the CCl4. Calculated ab initio values and semiempirical values for oxygen-17 and deuterium quadrupole coupling constants (chi) of water/CCl4 clusters are reported. Experimental values for the 17O, 2H, and 1H NMR spin-lattice relaxation times, T1, of 0.03 mole percent water in dilute CCl4 solution at 291 K are 94+/-3 ms, 7.0+/-0.2 s, and 12.6+/-0.4 s, respectively. These T1 values for bulk water are also referenced. "Experimental" values for the quadrupole coupling constants and relaxation times are used to obtain accurate, experimental values for the rotational correlation times for two orthogonal vectors in the water molecule. The average correlation time, tauc, for the position vector of 17O (orthogonal to the plane of the molecule) in monomer water, H2(17)O, is 91 fs. The average value for the deuterium correlation time for the deuterium vector in 2H2O is 104 fs; this vector is along the OD bond. These values indicate that the motion of monomer water in CCl4 is anisotropic. At 291 K, the oxygen rotational correlation time in bulk 2H2(17)O is 2.4 ps, the deuterium rotational correlation time in the same molecule is 3.25 ps. (Ropp, J.; Lawrence, C.; Farrar, T. C.; Skinner, J. L. J. Am. Chem. Soc. 2001, 123, 8047.) These values are a factor of about 20 longer than the tauc value for dilute monomer water in CCl4.

33S NMR spectroscopy 3. substituent effects on 33S NMR parameters in 2‐substituted ethanesulfonates

33S NMR parameters (chemical shifts and linewidths) in 2-substituted sodium ethanesulfonates, XCH2CH2SO3Na (X = H, CH3, OH, SH, NH2, Cl, Br, NH3+) depend upon the electronic properties of substituents. To explain experimental results and obtain additional information on the origin of the observed substituent effect (SE), sulfur isotropic absolute shielding constants have been calculated at DFT level of theory (B3LYP/6-311++G(2d,p)) by gauge-including atomic orbitals (GIAO) method. Data have been interpreted with the aid of natural bond orbital (NBO) method and natural chemical shielding (NCS) analysis. It has been demonstrated that in the class of compounds considered the diamagnetic contribution to sulfur-shielding constant is constant and the observed upfield shift of 33S resonance induced by electron-withdrawing substituents (reverse chemical shift effect) can be related to variations of the paramagnetic contribution. Substituents with different electronic properties cause variations in the polarization of S-C and S-O bonds of the -C-SO3- moiety thus determining changes of the electron density at sulfur nucleus and consequently the expansion or contraction of 3p sulfur orbitals. Also oxygen lone-pairs and sulfur core 2p electrons can play an active role in determining the paramagnetic contribution to sulfur shielding. With regard to linewidth variations, they can be ascribed primarily to changes in the nuclear quadrupole coupling constant values. B3LYP/6-311++G(2d,p) method allows obtaining a good reproducibility of SE on the electric field gradient (EFG) at sulfur, although its values tend to be underestimated significantly. Moreover, 17O shielding constants have been calculated.

A Systematic Investigation of Hydrogen-Bonding Effects on the 17O, 14N, and 2H Nuclear Quadrupole Resonance Parameters of Anhydrous and Monohydrated Cytosine Crystalline Structures: A Density Functional Theory Study

A systematic computational study was carried out to characterize the 17O, 14N, and 2H nuclear quadrupole resonance (NQR) parameters in the anhydrous and monohydrated cytosine crystalline structures. To include the hydrogen-bonding effects in the calculations, the most probable interacting molecules with the central molecule in the crystalline phase were considered in the pentameric clusters of both structures. To calculate the parameters, couples of the methods B3LYP and B3PW91 and the basis sets 6-311++G** and CC-pVTZ were employed. The mentioned methods calculated reliable values of 17O, 14N, and 2H NQR tensors in the pentameric clusters, which are in good agreements with the experiment. The different influences of various hydrogen-bonding interactions types, N-H...N, N-H...O, and O-H...O, were observed on the 17O, 14N, and 2H NQR tensors. Lower values of quadrupole coupling constants and higher values of asymmetry parameters in the crystalline monohydrated cytosine indicate the presence of stronger hydrogen-bonding interactions in the monohydrated form rather than that of crystalline anhydrous cytosine.

155Gd Mössbauer spectra of some Gd(III)-b-diketonato complexes

155Gd Mossbauer spectra of some Gd(III)-b-diketonato complexes are reported. All of their 155Gd Mossbauer isomer shift (d) values fall in a narrow range of +0.55-+0.65 mm.s-1, and are between those of GdF3 and the cubic form of Gd2O3. This indicates that their Gd-O bonds have small covalent character. The value for quadrupole coupling constant (e2qQ) spread out from 1.67 to 7.56 mm.s-1 and reflects the difference well in symmetry of the coordination polyhedron around Gd(III) ions for those Gd(III)-b-diketonato complexes.

Structure and Properties of Acidic Protons in Anhydrous Dodecatungstophosphoric Acid, H3PW12O40, As Studied by Solid-State 1H, 2H NMR, and 1H−31P Sedor NMR

The binding position and the electronic properties of acidic proton in anhydrous dodecatungstophosphoric acid, H3PW12O40, were studied by means of 1H, 2H NMR, and 1H−31P spin−echo double resonance (SEDOR) NMR techniques. 1H broad line NMR spectrum showed a bell-type resonance line shape with 4.7 kHz line width and MAS NMR spectrum has a single resonance peak, suggesting that the hetero-polyanion PW12O403- provides a single site to the acidic proton. 2H NMR spectrum leads to the quadrupole coupling constant (QCC) of 210 kHz and the asymmetry parameter of the electric-field-gradient tensor (η) of 0.15. The value of QCC suggests that the deuterons are bonded to oxygen atoms in the hetero-polyanion very rigidly, and that any motion of the hetero-polyanion does not take place. A remarkable decay of the 1H−31P SEDOR signal was observed, due to the dipolar interaction between the central 31P and three protons strongly bonded to the hetero-polyanion. The P−H distance was evaluated by simulating the decay behavior...

121Sb, 57Fe and 127I Mössbauer spectroscopic study on antimony-transition metal bond in metal carbonyl derivatives of tertiary stibines

Antimony-transition metal bonds in five- or six-coordinate [M(CO) n (SbR 3)] (M=Fe, Ru; n=4, M=Cr, Mo, W; n=5, R=Me, Ph), seven-coordinate [MI 2(CO) 3(SbPh 3)L] − (M=Mo, W, L=PPh 3, AsPh 3) and [MI 3(CO) 3(SbPh 3)] − (M=Mo, W) have been investigated using the 121Sb, 57Fe and 127I Mössbauer spectroscopy. Coordination of SbR 3 to the transition metal atom results in the increase in the values of isomer shift and the decrease in the values of quadrupole coupling constant of the 121Sb Mössbauer spectra. This indicates that the lone pair electron of the stibine is transferred to the transition metal atom. The degree of the transfer increases in the order of Mo<W<Ru, and Cr≪Fe, being the order of the Allred–Rochow's electronegativity for the transition metal atom. The same trend holds for [MI 2(CO) 3(SbPh 3)L] (M=Mo, W). 57Fe Mössbauer spectra of [Fe(CO) 4(SbR 3)] at 80 K are not so different from that of Fe(CO) 5, suggesting that some redistribution of electron density around Fe atom occurs. The 127I Mössbauer spectra for [MI 2(CO) 3(SbPh 3)L] and [MI 3(CO) 3(SbPh 3)] show a typical σ interaction in MI bonds.

Effect of Intermolecular Hydrogen Bonding on the Nuclear Quadrupole Interaction in Imidazole and its Derivatives as Studied by ab initio Molecular Orbital Calculations

Ab initio Hartree-Fock molecular orbital calculations were applied to the crystalline imidazole and its derivatives in order to examine systematically the effect of possible N-H---N type hydrogen bond-ing on the nuclear quadrupole interaction parameters in these materials. The nitrogen quadrupole coupling constant (QCC) and the asymmetry parameter (η) of the electric field gradient (EFG) were found to depend strongly on the size of the molecular clusters, from single molecule, to dimer, trimer and to the infinite molecular chain, i.e., crystalline state, implying that the intermolecular N-H -N hydrogen bond affects significantly the electronic structure of imidazole molecule. A certain correla-tion between the QCC of 14N and the N-H bond distance R was also found and interpreted on the basis of the molecular orbital theory. However, we found that the value of the calculated EFG at the hy-drogen position of the N-H group, or the corresponding QCC value of 2 H, increases drastically as R-3 when R is shorter than about 0.1 nm, due probably to the inapplicability of the Gaussian basis sets to the very short chemical bond as revealed in the actual imidazole derivatives. We suggested that the ob-served N-H distances in imidazole derivatives should be re-examined.

General theoretical formalism for describing the high-order effects of the dipolar coupling between spin-1/2 and quadrupole nuclei

A general theoretical description of the effect of the second-order dipolar coupling between spin-1/2 and quadrupole nuclei is presented based on the density operator formalism rather than the Shrödinger equation as in previous publications. The main task of this formalism is to diagonalize the evolution operator which can be performed analytically when the quadrupole nucleus is spin-1 or spin-3/2; no approximations such as the adiabatic assumption, perturbation expansion and the average Hamiltonian treatment are assumed. Therefore, it is general and can be used for all nuclear spins and any value of quadrupole coupling constant and in the case of magic-angle spinning (MAS) for any rotor spinning speed; it can also include the case when more than one species of spin-1/2 nuclei is coupled to the quadrupole nucleus. The effects of indirect dipolar coupling, chemical shift anisotropy and sample spinning speeds on Nuclear Magnetic Resonance (NMR) lineshapes can be uniformly incorporated in the formalism. Lineshape simulations based on this formalism can yield structural and electronic parameters of compounds and materials with high accuracy. Experimental results for several typical compounds of different complexities are demonstrated and are shown to be in good agreement with the theoretical spectral simulations.

Deuteron dynamics and its isotope effect in β-Ti 1− yV yDx as studied by 2H NMR

Deuteron dynamics and its isotope effect in disordered metal deuterides, β-Ti 1− y V y D x ( x∼1 and 0.2≤ y≤0.8) were studied by 2H NMR. Temperature dependence of 2H spin-lattice relaxation times ( T 1) was measured over the temperature range 125–400 K. All the deuterides exhibited a minimum in ln( T 1) vs. 1/T curves, which originated from the fluctuation of the quadrupole interaction due to the deuteron diffusion. The quadrupole coupling constant (QCC) for the deuteron and the activation parameters were determined from the T 1 data analysis with Bloembergen-Purcell-Pound (BPP) theory taking account of the distribution of the correlation time. The QCC values, which were within the range of 21∼36 kHz, made it possible to assign the deuteron site in the alloys to the tetrahedral site. The remarkable isotope effect was found in the activation energy E a for the hydrides and the deuterides. The difference in the E a between the deuterides and the hydrides, E a D− E a H, was interpreted qualitatively by the atomic mass effect and the difference in the manner of site occupation between the hydrides and the deuterides.