Showing papers by "Robert Blinc published in 1984"
85 citations
TL;DR: In this article, the temperature dependence of the 13C NMR chemical shifts has been measured in the isotropic, the smectic A and C* phases of chiral DOBAMBC and HOBACPC.
Abstract: The temperature dependence of the 13C NMR chemical shifts has been measured in the isotropic, the smectic A and the smectic C* phases of chiral DOBAMBC (p-decyloxybenzylidene p′-amino 2-methyl butyl cinnamate) and HOBACPC (hexyloxybenzylidene p′-amino 2-chloro α propyl cinnamate). The measurements allowed for a microscopic determination of the temperature dependence of the molecular tilt angle and the dipolar ordering of the C=O groups-i.e. the in-plane spontaneous polarization-without destroying the helical structure.
42 citations
40 citations
TL;DR: In this article, the temperature dependence of the helical pitch in the DOBAMBC near the C*-A transition has been measured with a high temperature resolution and the consistency of the data with different theoretical models is studied.
Abstract: The temperature dependence of the helical pitch in the ferroelectric liquid crystal DOBAMBC near the C*-A transition (T c ) has been measured with a high temperature resolution. The pitch strongly decreases with temperature near the transition but reaches a finite value at T c. The consistency of the data with different theoretical models is studied.
30 citations
TL;DR: In this article, a model involving not only chiral but also non-chiral biquadratic coupling between the polarization and the tilt has been proposed to explain the anomalous behaviour of the critical magnetic field and the helical pitch in the vicinity of the Λ-line and the Lifshitz point in the ferroelectric liquid crystal DOBAMBC.
Abstract: In order to explain the anomalous behaviour of the critical magnetic field and the helical pitch in the vicinity of the Λ-line and the Lifshitz point in the ferroelectric liquid crystal DOBAMBC a model involving not only chiral but also non-chiral biquadratic coupling between the polarization and the tilt has been proposed The model predicts an “S - like” dependence of the modulation wave vector close to the smectic C* - smectic A transition High temperature resolution measurements of the helical pitch and the intensity of the diffraction sattelites indeed support the proposed model and seem to show that the pitch is finite at Tc In such a case the Lifshitz field HL is finite too
24 citations
22 citations
TL;DR: In this paper, the temperature dependence of the 17O nuclear quadrupole double-resonance spectra of squaric acid has been measured and the electric field gradient tensors at 17O H--O and 17O---H O sites have been determined from −5 to 144°C.
22 citations
TL;DR: In this paper, the transition between the incommensurate plane-wave modulation regime and the multisoliton lattice modulation regime is studied by 87Rb quadrupole perturbed nuclear magnetic resonance in Rb2ZnCl4.
Abstract: The transition between the incommensurate plane-wave modulation regime and the multisoliton lattice modulation regime is studied by 87Rb quadrupole perturbed nuclear magnetic resonance in Rb2ZnCl4. Both phase and amplitude solitons are taken into account in comparing the experimental and theoretical lineshapes and determining the soliton density. Commensurate lines are clearly seen already in the middle of the incommensurate phase demonstrating that multisoliton lattice effects are important over a much wider temperature range than reported previously.
18 citations
TL;DR: The hydrogen bond dynamics of pseudo-one-dimensional CsH2PO4 has been studied in the paraelectric and ferroelectric phases by 17O-proton nuclear double resonance spectroscopy as discussed by the authors.
Abstract: The hydrogen bond dynamics of pseudo‐one‐dimensional CsH2PO4 has been studied in the paraelectric and ferroelectric phases by 17O–proton nuclear double resonance spectroscopy. The results show that the protons in the short one‐dimensionally linked O–H(2)‐‐O hydrogen bonds are moving between two equilibrium sites above Tc and freeze into one of the two off‐center sites below Tc. The protons in the asymmetric O–H(1)‐‐O bonds are static and ordered in the same way both above and below Tc and seem to play only a minor role in the transition mechanism.
12 citations
TL;DR: In this paper, a partial motional averaging of the splitting between the two edge singularities in the 35 Cl nuclear quadrupole resonance spectrum was proposed, and the mean square phase fluctuations were close to T I proportional to (T I − T ) −2β with β = 0.39 ± 0.04.
11 citations
TL;DR: In this article, it was pointed out that the huge observed differences in the soft mode frequencies of PbHPO4, CsH2PO4 and squaric acid do not necessarily reflect a large difference in the proton 0-H−O tunneling frequencies but rather result from a difference in short range correlations renormalizing the single proton O−H−o tunneling frequency.
Abstract: It is pointed out that the huge observed differences in the soft mode frequencies of KH2PO4, PbHPO4, CsH2PO4 and squaric acid do not necessarily reflect a large difference in the proton 0—H———O tunneling frequencies but rather result from a difference in the short range correlations renormalizing the single proton O——H—O tunneling frequency.
TL;DR: The appearance of a liquid-like proton T2 component above 100°C and the relatively high value of the proton self-diffusion coefficient D = (5-8) × 10-7 cm2 sec-1 between 175°C to 200°C demonstrate the onset of a super-ionic state in N(CH3)4HSO4.
TL;DR: In this article, the frequency dispersion of the proton spin-lattice relaxation rates T−1 1 in the ferroelectric smectic phases of DOBAMBC has been determined in the MHz region and analyzed in terms of the order fluctuations, self-diffusion, and rotational contributions.
Abstract: The frequency dispersion of the proton spin-lattice relaxation rates T−1 1 in the ferroelectric smectic phases of DOBAMBC has been determined in the MHz region and analyzed in terms of the order fluctuations, self-diffusion, and rotational contributions to T−1 1. In the smectic C* phase the main rate determining contribution are order fluctuations with a T−1 1 ∝ ν−1/2 L frequency dependence, whereas in the smectic H* phase the translational diffusion, which is slower than in the smectic H* phase, determines the dispersion of T−1 1.
TL;DR: In this paper, temperature dependences of the dielectric constant and of the helical pitch have been measured for the mixture of 4-n-butiloxybenzylidene-4−n-octylaniline, 12.92 wt.
Abstract: Temperature dependences of the dielectric constant and of the helical pitch have been measured for the mixture 71.76 wt.% of 4-n-butiloxybenzylidene-4′-n-octylaniline, 12.92 wt.% of 4–4′-bis-n-heptyloxy-azoxybenzene and 15.32 wt.% of 4″-(2-methylbutylphenyl)-4′-(2-methylbutyl)-4-biphenylcarboxylate which is in the ferroelectric helicoidal smectic C* phase at room temperature. The anomalies close to the smectic C*-smectic A transition are of the same type as in DOBAMBC and cannot be understood in terms of the standard Landau free energy expansion.
TL;DR: In this article, the deuteron motion freezes out at Tc2 and the spin-lattice relaxation time is determined in the high temperature paraelectric phase, T > Tc1, the intermediate phase, TCI > T >Tc2, and the low temperature phase T < Tc 2.
Abstract: The 87Rb electric field gradient tensors and spin-lattice relaxation rates of monoclinic RbD2PO4 are determined in the high temperature paraelectric phase, T > Tc1, the intermediate phase, TCI > T > Tc2, and the low temperature phase T < Tc2. The transitions between these phases are of second order and are connected with significant changes in the 87Rb and deuteron quadru-pole coupling. The temperature dependence and anomalously short values of the 87Rb spin-lattice relaxation time seem to reflect the pseudo-one-dimensional nature of the correlations in the deuteron motion between the two potential minima in the ODO bonded chains along the b-axis. The deuteron motion freezes out at Tc2.
Die Tensoren des elektrischen Feldes von 87Rb und die Spin-Gitterrelaxationszeiten von mono-klinem RbD2PO4 werden in der paraelektrischen Hochtemperaturphase T > Fc1, der Zwischen-phase Tc1 > T > Tc2 und der Tieftemperaturphase T < Tc2 bestimmt. Die ubergange zwischen diesen Phasen sind von zweiter Ordnung und mit betrachtlichen anderungen der Quadrupolkopplung von 87Rb und Deuteriumkernen verknupft. Die Temperaturabhangigkeit und die anomal kleinen Werte der Spin-Gitterrelaxationszeit fur 87Rb scheinen die pseudo-eindimensionale Natur der Korrelation in der Deuteronbewegung zwischen den beiden Potentialminima in den ODO-Bindungsketten in Richtung der b-Achsen wiederzuspiegeln. Die Deuteronbewegung scheint bei Tc2 auszufrieren.
TL;DR: The translational diffusion of amphiphile molecules in lyotropic nematic phases has been studied for different orientations of the pulsed magnetic field gradient using the magic angle NMR spin-echo as discussed by the authors.
Abstract: The translational diffusion of amphiphile molecules in lyotropic nematic phases has been studied for different orientations of the pulsed magnetic field gradient using the magic angle NMR spin-echo...
TL;DR: In this paper, the dielectric constant of deuterated ammonium Rochelle salt along three crystallographic axes as well as the pyroelectric charge density developed on the crystal surface perpendicularly to the b-axis have been measured with a high temperature resolution.
TL;DR: The deuteron quadrupole coupling constant eQV zz / h in squaric acid amounts at room temperature to 142 ± 2 kHz and the asymmetry parameter η is 021 as discussed by the authors.