Deuteron Quadrupole Coupling Constants Research Articles

Deuteron Quadrupole Coupling in Some Solid Chlorinated Hydrocarbons

We report deuteron quadrupole coupling constants in solids CDCl3, CD2Cl2, CD2ClCD2Cl, CD3CCl3, and CD3CCl2CD3. At 77°K these are 167.6 ± 0.8, 169.6 ± 1.1, 171.7 ± 0.8, 174.3 ± 1.6, and 174.7 ± 1.9 kHz, respectively, assuming an axial quadrupole interaction. We also report here a coupling constant of 149.3 ± 0.5 kHz for D in DCl at 77°K, in agreement with the data of Genin, O'Reilly, Peterson, and Tsang. Deuteron pure quadrupole spectra were observed by a pulse double-resonance technique suggested by Hahn and co-workers, in which the halogen serves as indicator nucleus. Interpretation of the results in terms of the electronic structure is briefly discussed.

Study of isotopic effects and determination of the quadrupole coupling constant from the nuclear magnetic resonance spectra of monodeuterobenzene in a nematic phase

The proton and the deuteron magnetic resonance spectra of monodeuterobenzene have been studied in the nematic phase of a mixture of 50% 4-methoxybenzylidene-4-amino-α-methyl cinnamic acid-n-propyl ester and 50% anisole–azophenyl-n-capronate at room temperature.The proton spectrum is studied as a superposition of three 5-spin sub-spectra due to coupling with one deuteron (spin I = 1) and analyzed iteratively as a 7-spin system, treating the deuteron as two spin [Formula: see text] particles.The values of the dipole–dipole couplings show minor but significant deviations due to isotopic substitution, from those expected for the regular hexagonal geometry. Two parameters are necessary to define molecular orientation. The ratio of the two orientation parameters is reported.The ratios (rHD/rHH)ortho and (rCH − rCD)/(rHH)ortho are obtained. They indicate a reduction in the time average value of the C—D bond length compared to the C—H one.It is suggested that the orientation parameters from the proton spectrum of the molecule are used in order to determine the deuteron quadrupole coupling constant from deuteron magnetic resonance (d.m.r.) spectra of partially deuterated molecules dissolved in the nematic phase. The method is applied to the present case. Its limitations and the sources of errors are discussed.

Proton and Deuteron NMR of Ice Polymorphs

Proton and deuteron nuclear magnetic resonances in the H2O and D2O ice polymorphs have been recorded at 60 MHz and at 8 MHz, respectively. Proton rigid-lattice second moments have been obtained at 75°K for ices Ih, Ic, II, V, VI, and IX. The modulation-corrected experimental values of the second moments ranged from 32.2 G2 in ice Ic to 37.9 G2 in ice VI. Theoretical inter- and intramolecular contributions to the second moments of these ices have been made, with corrections applied to the latter for librational and vibrational motions after the manner of Pederson. These theoretical results when compared with experimental values strongly support the bent hydrogen-bond model with an H–O–H angle near 104°, in agreement with conclusions reached from our recent neutron-diffraction pattern analyses of ices Ic, II, and IX. Deuteron quadrupole coupling constants for ices Ic, II, V, and IX have been estimated from derivative of dispersion traces by comparison with the ice Ih signal obtained under similar experimental conditions. Because of saturation effects, it was not possible to record deuteron resonances at the temperature of liquid nitrogen; however, signals were recorded at temperatures slightly below the respective phase-transition temperatures for these ice polymorphs. From the relatively constant values of e2qQ / h observed for these ices, it appears that the O–D bond distance is essentially unchanged in the different ice forms. This generalization is also supported by the results of neutron-diffraction studies.

Deuteron magnetic resonance studies. Part 1.—Calculated deuteron quadrupole coupling constants for deuterium fluoride and chloride

The deuteron quadrupole coupling constants of deuterium fluoride and deuterium chloride have been calculated for several wave-functions with extended basis sets using the Barnett and Coulson expansions to evaluate the necessary integrals. Values in DF of 363 ± 1 and 354 ±1 kc/sec at an internuclear distance of 0.917 Å were found from two wave-functions of Nesbet and 374 ± 10kc/sec at 0.915 Å from a one-centre wave-function of Moccia. In DCl, a wave-function of Scrocco and Tomasi gave a value of 213 ± 2 kc/sec. The agreement with experiment is discussed.

Deuteron magnetic resonance in solid and liquid SiD 4 above 36°K

Deutron magnetic resonance in SiD 4 has been studied by the absorption and pulse methods between 36 and 156°K. The solid state phase transition temperature is measured as 67 − 1°K. For the deuteron quadrupole coupling constant the value 95 kHz is obtained. Rotational potential barriers are discussed.

The deuteron quadrupole coupling constant in the deuteroxide ion

The deuteron quadrupole coupling constant and asymmetry parameter of the OD − ion in LiOD·D 2O are 267.7 kc/s and 0.044 at 273°K and 271.5 and 0.043 at 77°, compared to a theoretical estimate of 421 kc/s for the free ion from recent LCAO-MO-SCF wave-functions.

Deuteron Quadrupole Coupling Constant in CH3D

The deuteron electric-field gradient qD and quadrupole coupling constant (eqQ/h)D for CH3D have been calculated from extended basis-set LCAO-MO-SCF wavefunctions determined by Woznick for this system. Comparison of the results for different wavefunctions and different distances suggest that a reasonable theoretical estimate is (eqQ/h)D=210±30 kc/sec. Since this disagrees significantly with the present experimental estimate [(eqQ/h)D=100±50 kc/sec], a more refined measurement would be desirable. Simplified schemes are examined for calculating (eqQ/h)D with neglect of three-center integrals or introduction of a two-center model; errors of 5% to 20% result.

On the deuteron magnetic resonance in single crystals of ND4Cl and ND4Br

The deuteron quadrupole coupling constants in ND4Cl and ND4Br have been measured. The results are 179.9±2.0 and 180.0±2.0 kHz, respectively. From the temperature dependence of the line width in ND4Cl for the d. c. magnetic field along [100] the hindered rotation potential barrier of the ND4+-ion was found to be 5.1 kcal/mole. In crystals containing moisture a narrow line component was observed, which is probably due to the formation of an eutectic solution.

Nuclear Quadrupole Coupling in Polyatomic Molecules

The Gaussian-transform method has been applied to the evaluation of the deuteron and nitrogen-14 quadrupole coupling constant (eqQ/h) with the various minimal and extended basis-set SCF—LCAO—MO functions that are available for the linear polyatomic molecules DCN, C2D2, DF2—, and N3—. Comparisons are made between calculations neglecting and including the three-center integral contributions. The coupling constant is found to be quite sensitive to the choice of basis orbitals, particularly those responsible for the form of the valence-shell charge density. This suggests that the quadrupole coupling constant in polyatomic molecules is a useful criterion for testing the wavefunction obtained in approximate calculations. Of particular interest is the variation in the (eqQ/h)D results for DF2—, which points out the need for an experimental coupling constant measurement for this hydrogen-bonded species.

Hyperfine Structure in the Microwave Spectrum of HDO, HDS, CH2O, and CHDO : Beam-Maser Spectroscopy on Asymmetric-Top Molecules

Hyperfine structure in the 220→221 rotational transition of HDO at 10 278.2 Mc/sec and HDS at 11 283.8 Mc/sec, and in the 211→212 rotational transition of CH2O at 14 488.6 Mc/sec and CHDO at 16 038.1 Mc/sec, has been investigated with a high-resolution beam maser microwave spectrometer. Linewidths of 5 kc/sec have been obtained. The hyperfine Hamiltonian for an arbitrary number of nuclei with quadrupole, spin—rotation, and spin—spin interactions is discussed, and the matrix elements of the Hamiltonian and the intensities of hyperfine transitions calculated in terms of the tabulated 6j coefficients. Quadrupole and spin—rotation constants and bond lengths which have been determined are, for the 220 state of HDO: (eqJQ)D = 79.3±0.3 kc/sec, CH = —43.47±0.11 kc/sec, CD = —2.33±0.02 kc/sec; for the 221 state of HDO: (eqJQ)D = 79.6±0.3 kc/sec, CH = —43.63±0.13 kc/sec, CD = —2.20±0.02 kc/sec; for the 220 state of HDS: (eqJQ)D = 42.9±0.4 kc/sec, CH = —25.03±0.13 kc/sec, CD = —0.47±0.02 kc/sec; for the 221 state of HDS: (eqJQ)D = 43.3±0.4 kc/sec, CH = —25.45±0.13 kc/sec, CD = —0.22±0.02 kc/sec; for CH2O: CH (211) — CH (212) = 2.26±0.13 kc/sec, CH (211) = 0.65±0.50 kc/sec, 〈1/rHH3〉—⅓ = 1.898±0.017 Å; for CHDO: (eVξξQ)D = 170.0±2.0 kc/sec (where Vξξ is the second derivative of the electrostatic potential along the CD bond), CH (211) — CH (212) = 2.42±0.50 kc/sec, CD (211) — CD (212) = 0.25±0.10 kc/sec, CH (211) = 0.2±1.0 kc/sec, CD (211) = 0.13±0.20 kc/sec, and 〈1/rHD3〉—⅓ = 1.88±0.10 Å. The Vξξ calculated from the deuteron quadrupole coupling constants are, for HDO: 1.56×1015 statvolt/cm2; for HDS: 0.76×1015 statvolt/cm2; and for CHDO: 0.83×1015 statvolt/cm2.

Deuteron Quadrupole Coupling in Diatomic ``Hydrides''

For LiD and DF, the deuteron quadrupole coupling constant (eqQ/h) has been calculated with single-determinant SCF-LCAO-MO functions. The results obtained are 38 kc/sec for LiD and 373 kc/sec for DF, in rather satisfactory agreement with the recently measured values (30±3 kc/sec for LiD and 340±40 kc/sec for DF). To evaluate the molecular integrals required for the determination of q, a formulation in terms of confocal elliptic coordinates was used. This made possible the introduction of certain auxiliary functions that are very convenient for the calculation of field gradient and related integrals. A comparison of the quadrupole coupling constants obtained with a number of different molecular orbital functions is presented. The results demonstrate the importance of using atomic basis functions with exponents optimized for the molecular system and suggest that exact Hartree-Fock functions may yield relatively reliable values for field gradients and other one-electron weak-interaction parameters. A calculation of the field gradient at the Li nucleus (q = —0.0401 a.u.) yields a value of —3.7×10—26 cm2 for the Li7 quadrupole moment when combined with the coupling constant measurement of +346±1 kc/sec.

Ground-State Inversion Spectrum of N14D3

The inversion spectrum of N14D3 has been investigated between 1500 and 1620 mc/sec. A revised formula for the rotational fine structure was obtained to fit 17 observed lines. Splitting of K = 3 lines into two components was found in good agreement with predicted values. Nitrogen satellites were observed and the values (eQq)N = 4080–3 kc/sec and α = 2±2 kc/sec were assigned to the nitrogen quadrupole and magnetic coupling constants, respectively. Hyperfine structure due to removal of the K degeneracy was observed in K = 1 lines. Applying the theory of Hadley, calculated and observed line contours were brought into agreement. Assuming cylindrical symmetry about bonds, the value (eQq)D = 200±20 kc/sec was obtained for the deuteron quadrupole coupling constant. A value ε = 1.9±0.5 kc/sec was obtained for the magnetic coupling constant between deuteron spins and molecular rotation.

Theoretical Study of the Hyperfine Structure in the Inversion Spectra of the Deutero-Ammonias

The energy splittings in the inversion spectra of N14D3, N14HD2, and N14DH2 caused by nitrogen and deuteron quadrupole interactions with the molecular electric field, the interactions of the nuclear spins with the molecular magnetic field, and the spin-spin interactions are found. The molecular coupling scheme of Van Vleck is used to treat the Hamiltonian to second order in the electronic energies. Group theory is used to select wave functions which simplify the solution of the secular equations. For N14D3 thirteen constants appear in the energy expressions. Order of magnitude estimates for eleven of these constants can be made using data from the experimental work on N14H3. No estimate is made of the deuteron quadrupole coupling constants. With N14HD2 and N14DH2 twenty-four constants appear in each case. Order of magnitude estimates can be made for only nine of these.