ZfN: Search Results

1	Author	Hiroshi Ohki, Nobuo Nakamura	Requires cookie*
	Title	Sodium Ion Exchange in Na 1+x Zr 2 Si x P 3 _ ;c 0 1 2 as Studied by 23 Na Nutation NMR
	Abstract	23 Na two-dimensional nutation NMR was applied to Nat + *Zr2SivP3_vO,2 with x = 0, 1, and 2. The nutation spectrum in each compound consists of two clearly separated peaks corresponding to the two crystallographically inequivalent sodium sites. In the compound with x = 2 the nuclear quadrupole coupling constants (e Qq/h) and the asymmetry parameters (rj) were by spectral simu-lation estimated to be 1.0 MHz and 0 for one site, and 1.5 MHz and 0.8 for the other site. The spectrum varies considerably on heating; the two peaks merge into a single peak at high tempera-tures due to fast ion exchange between the two different sites. For x = 0 and x = 1 the nutation spectra did not show any significant temperature dependence, suggesting that the rates of the sodium ion exchange are negligibly low.
	Reference	Z. Naturforsch. 47a, 319—324 (1992); received August 10 1991
	Published	1992
	Keywords	Nutation NMR, Quadrupole effect, Superionic conductor, Chemical exchange
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	TEI-XML for	default:Reihe_A/47/ZNA-1992-47a-0319.pdf
	Identifier	ZNA-1992-47a-0319
	Volume	47

2	Author	V. P. Tarasov, G. A. Kirakosyan, K. E. German, Acad Sei, Ussr	Requires cookie*
	Title	Anomalous Temperature Dependence of the "Tc Quadrupole Coupling and Disordering of Cesium Positions in CsTc0 4
	Abstract	A "Tc and 133 Cs solid-state NMR study of polycrystalline CsTc04 at a field of 7.04 T and temperatures from 90 to 430 K revealed first-order quadrupole effects. "Tc quadrupole coupling constant, Cq, shows anomalous positive temperature coefficients and decreases from 2.0 MHz at 430 K to 0.45 MHz at 90 K. The asymmetry parameter, rj ("Tc), is zero at 430 K and at 210 K. The high-temperature minimum of rj is associated with a phase transition from orthorhombic to tetrag-onal and the second minimum reflects an orientational change of the principal axes q xx and q yy of the EFG-tensor. The 133 Cs NMR spectra are characterised by a superposition of the two powder multiplets from the first-order couplings which arise from magnetically and crystallographically nonequivalent cesium sites, Cs (1) and Cs (2); the population ratio of Cs (2) and Cs (1), p2/p1, varies from 2.0 at 120 K to 6.5 at 373 K. The nonequivalence and population changes are attributed to the temperature change of the crystal field potential in the vicinity of the cations.
	Reference	Z. Naturforsch. 47a, 325—329 (1992); received July 26 1991
	Published	1992
	Keywords	Technetium, Cesium, Solid State NMR, Quadrupole Effects, Phase Transitions
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	TEI-XML for	default:Reihe_A/47/ZNA-1992-47a-0325.pdf
	Identifier	ZNA-1992-47a-0325
	Volume	47

3	Author	PascalP M An	Requires cookie*
	Title	Solomon Echoes Extended to Soft Pulse Excitation
	Abstract	Solomon echoes, produced by two in-phase pulses separated by a delay r2, are derived in taking into account the first-order quadrupolar interaction during the pulses. Consequently, the results are valid for any ratio of the quadrupolar coupling, coQ, to the amplitude of the radiofrequency pulse, <yRF. Six echoes are predicted after the second pulse: three, detected as inner satellite signals, occur at t 4 = r2, t 4 = 2 t 2 and t 4 = 3 1 2; the other three, detected as outer satellite signals, occur at t 4 = r 2 /2, t 4 = t 2 , and t4 = 3 t 2 /2. These echoes originate from the refocusing of single-and multi-quantum off-resonance coherences developed during the first pulse. Four of them are allowed echoes, the other two are forbidden ones. However, there is no echo for the central transition. From a practical point of view this means that r2 must be short compared to TFID, the duration of the FID of the central transition. The behavior of the echo amplitude versus the second pulse length is discussed for several ratios of coQ/coRF.
	Reference	Z. Naturforsch. 49a, 89 (1994); received July 23 1993
	Published	1994
	Keywords	Quadrupole effect, Spin-5/2, Spin echo NM R, Solomon echoes
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	TEI-XML for	default:Reihe_A/49/ZNA-1994-49a-0089.pdf
	Identifier	ZNA-1994-49a-0089
	Volume	49

4	Author	S. V. Verkhovskii, B. Z. Malkin, A. Trokiner, A. Yakubovskii, E. Hallet, A. Ananyev, A. Gerashenko, Yu Piskunov, S. Saikin, A. Tikhomirov, V. Ozhogin	Requires cookie*
	Title	Quadrupole Effects on 73 Ge NMR Spectra in Isotopically Controlled Ge Single Crystals
	Abstract	NMR spectra of 73 Ge (nuclear spin / = 9/2) in perfect single crystals of germanium with different isotopic content were measured at 80, 300, and 450 K. The observed specific line shapes gave evidence of the isotopic disorder, in particular, abnormal broadening of the spectrum was found for the magnetic field directed along the [111] axis. Local lattice deformations in the germanium crystal lattice due to "isotopic disorder" were calculated in the framework of the adiabatic bond charge model. The results were applied to study random non-cubic crystal field interactions with the nuclear quadrupole moments and corresponding effects on NMR spectra. The simulated second moment of the resonance frequency distributions caused by the magnetic dipole-dipole and electric quadrupole interactions are used to analyze the lineshapes, theoretical predictions being in a qualitative agreement with the experimental data.
	Reference	Z. Naturforsch. 55a, 105—110 (2000); received September 11 1999
	Published	2000
	Keywords	Isotopic Disorder, Ge Single Crystal, NMR Spectra, Quadrupole Effects
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	TEI-XML for	default:Reihe_A/55/ZNA-2000-55a-0105.pdf
	Identifier	ZNA-2000-55a-0105
	Volume	55