Halogan nuclear quadrupole resonance in tetrahedral halo complexes of zinc

Abstract

Halogen nuclear quadrupole resonance data are presented for a number of compounds containing tetrahedral ZnX42- ions, where X = Cl, Br, and I. Characteristic mean frequencies are: for 35Cl in ZnCl42- 8.9 MHz ; for 81Br in ZnBr42- 60 MHz; and for 127I in ZnI42- 75 and 150 MHz. The number and relative intensities of the resonances for any compound is found to be a useful indication of the site symmetry of the ZnX42- ion, and compounds of unknown structure are examined in this light. 35Cl data are also presented for Cs2CuCl4, which has a mean frequency of 10.6 MHz at 298�K.

Spin 3/2 Zeeman perturbed NQR in the presence of slow sample rotation

“…For our sample this line is inhomogeneously broadened with a FWHM of about 70 kHz and exhibits a spin-spin relaxation time, T 2 , measured using a Hahn echo, of 96 and 400 ls in Earth's field and in magnetic fields greater than about 10 G, respectively. This resonance has been assumed to correspond to g % 0 [15] which we verified by looking at the powder line shape in the presence of a magnetic field parallel to the RF coil axis [16,17]. The p-dichlorobenzene was obtained from a local merchant (sold as ''Moth Flakes'') and was ground into a fine powder.…”

The incommensurate phase of

“…If the discriminant is positive, one usually finds four real decay constants, two positive and two negative (the latter correspond to approach of the C-state values from x > X and are of no interest); imaginary solutions are occasionally found. With a the smaller of the two positive decay constants, the second-order interaction energy is F (2) inter (X)…”

“…If the discriminant is negative, on the other hand, the transition is unambiguously first order. The second-order interaction energy is formally F (2) inter (X) and so equation (A11) simplifies to…”

“…In some of the literature, the analysis for complex decay constants is stopped at equation (A11), leading to the incorrect conclusion that the second-order interaction energy has the form F (2) inter /L = exp(−2α R X)[C 1 + C 2 cos(2α I X + ψ)]/X with C 1 = 0; the possibility of a second-order transition (when C 1 > |C 2 |) is firmly denied by equation (A13). The equivalent of equation (A12) was used for a CDW model in [20] (which did not simplify the second square bracket).…”

“…The compound Cs 2 ZnI 4 belongs to the K 2 SeO 4 family of incommensurate systems [1], but is distinguished from the majority by a commensurate modulation k C = a * /2 (rather than k C = a * /3). Various physical properties of Cs 2 ZnI 4 have been investigated by a variety of experimental techniques [2][3][4][5][6][7][8][9][10][11][12]: nuclear quadrupole resonance [2,5,6], xray [2,5,6,10], dielectric constant [3,5,6], Raman scattering [4,9], nuclear magnetic resonance [5], optical birefringence [7,8,9], and heat capacity methods [11,12]. Cs 2 ZnI 4 has five phases [8,9,12]: P nma (Z = 4) ↔ incommensurate ↔ ferroelastic P 2 1 n (Z = 8) ↔ ferroelastic P 1 ↔ ferroelastic P 1; the respective transitions occur at T I = 117 K (second order), T L = 108 K (first order), 104 K (second order) and 94 K (first order).…”