Gen Soda

Deuteron Magnetic Resonance Study of Cupric Sulfate Pentahydrate

A deuteron magnetic resonance study is made of single crystals of CuSO4·5D2O between 130° and 360°K. The electric quadrupole coupling constant, the asymmetry parameter, and the directions of the principal axes of the field‐gradient tensor are determined for each deuteron at 133.2° and 294.8°K. At low temperatures ten pairs of lines are observed, corresponding to five nonequivalent stationary water molecules. At temperatures above room temperature, five pairs of lines are observed; these are shown to result from fast molecular reorientation about the bisecting axis of each water molecule. An activation energy for the 180° reorientational motion is derived for each water molecule and is discussed in relation to the lonepair coordination of the oxygen atom of the water molecule and the hydrogen‐bond strength. The field‐gradient tensor for each stationary water molecule is discussed in relation to the structure of the hydrogen‐bond system. For relatively weak asymmetric hydrogen bonds of O–H···O, an empirical...

Note on the Theory of Nuclear Spin Relaxation Exact Formulae in the Weak Collision Limit

A general relation exists between the relative magnitude of the power spectra J ( m ) (ω) that appear in the expressions of nuclear spin relaxation times T 1 , T 2 and T 1ρ of powdered specimen, i.e. J (0) (ω): J (1) (ω): J (2) (ω)=6:1:4. the relation holds exactly in the weak collision case irrespective of the modes of motion responsible for the relaxation. The proof is based on the symmetry properties of the spherical harmonics of rank two and therefore applicable not only to dipole-dipole but also to quadrupole coupling interaction and other problems. The reduction factor of the second moment of the nuclear magnetic resonance that results from a type of molecular motion also bears a simple general relation to the minimum value of T 1 due to the motion.

Deuteron Magnetic Resonance Study of Cupric Formate Tetrahydrate Cu(DCOO)2·4D2O

Deuteron magnetic resonance (DMR) of single crystals of Cu(DCOO) 2 ·4D 2 O has been studied from 153°K to 291°K to reveal the changes in the structure and the motions of the crystalline water molecules due to the paraelectric-antiferroelectric phase transition ( T c =246.1±0.2°K). Above T c , all the DMR lines of water molecules are broadened out by fast motions of deuterons among seven sites. Below T c , 20 pairs of DMR lines are observed corresponding to four water molecules in stable position and two formate ions and their a c -plane enantiomorphs. Following conclusions are derived from measurements of temperature and angular dependences of the quadrupole splittings for these DMR lines. The phase transition is an order-disordering type of water molecules. In the antiferroelectric phase, the unit cell doubling occurs along the c -axis direction and the space group is P 2 1 / n . The structure involves a three dimensional ordering of water molecules. The structure of hydrogen-bond network is determined. ...

Hydrogen-Bond Network and Ferroelectric Transition in Sodium Trihydrogen Selenite, NaD3(SeO3)2 by Nuclear Magnetic Resonance Study

Deuteron and 23 Na magnetic resonances are measured of single crystals of NaD 3 (SeO 3 ) 2 between 134°K and 298°K to reveal the nature of the ferroelectric transition ( T c ∼267°K). Deuteron resonance lines D a and D b (relative intensity 1:2) above T c split into two and into four, respectively. The 23 Na resonance line above T c also splits into two below T c . Following conclusions are derived from measurements of temperature and angular dependences of the quadrupole splittings for these deuteron and 23 Na resonance lines. All the hydrogen atoms are linked with moderately strong hydrogen bonds, and are jumping back and forth in the double well potential above T c . The phase transition is accompanied not only by order-disordering of hydrogen atoms in hydrogen bonds, but also by slight rotations of SeO 3 - ions and by a slight distortion of lattice in the neighborhood of Na + ions. The crystalline symmetry below T c is monoclinic, and the cell-doubling occurs along the b axis. Hydrogen-bond network bel...

Hydrogen-Bond Network in Ferroelectric Lithium Trihydrogen Selenite, LiD_3(SeO_3)_2 by Deuteron Magnetic Resonance

Deuteron magnetic resonance study is made of single crystals of LiD 3 (SeO 3 ) 2 between -143°C and 110°C. The electric quadrupole coupling constant, e Q q / h , the asymmetry parameter, η, and the directions of the principal axes of the field-gradient tensor are determined for each deuteron at room temperature. Three non-equivalent tensors are obtained corresponding to the three non-equivalent fairly strong hydrogen bonds determined by X-ray diffraction. The e Q q / h and η are 107.8 kc/sec and 0.172 for D a , 127.9 kc/sec and 0.154 for D b , and 181.1 kc/sec and 0.101 for D c , The hydrogen-bond network in LiD 3 (SeO 3 ) 2 is determined. The atomic coordinates of deuterons are estimated from the results of the present DMR study. The field-gradient tensor of 7 Li is also determined at room temperature. The values of e Q q / h and η are 33.9 kc/sec and 0.593.

Ferroelectric Phase Transition in Ammonium Hydrogen Bis(Chloroacetate). V. Nuclear Magnetic Resonance of NH4H(CH2ClCOO)2 and ND4D(CH2ClCOO)2

Proton resonance line shape and spin-lattice relaxation time T 1 were measured for polycrystalline NH 4 H(CH 2 ClCOO) 2 in ferro- and para-electric phases. Peculiar line shape and its temperature variation were ascribed to increasing tunnel splitting between the A and T symmetry levels in the librational ground state of NH 4 + ion from 15 kHz at 23 K to 20 kHz at 60 K. This increase corresponds to a decrease of rotational potential barrier (14.6 kJ mol -1 at 0 K) and a decrease of the ferroelectric order. Deuteron resonance line shape and T 1 were also measured for polycrystalline ND 4 D(CH 2 ClCOO) 2 . An extra line-width below T c was proportional to ( T c - T ) 0.76 ±0.09 . An activation energy of NH 4 + and ND 4 + reorientation above the transition point, 10.9 kJ mol -1 , was deduced from the T 1 data.