Search results for "dipole"

Frequency Dependence of the Orientational Freezing in(KBr)1−x(KCN)x

1982

Dielectric, ultrasonic, and neutron-scattering measurements in ${(\mathrm{KBr})}_{1\ensuremath{-}x}{(\mathrm{KCN})}_{x}$ are reported for concentrations $x$ ranging from 0.01 to 0.5. The dipolar and the quadrupolar susceptibilities exhibit frequency- and concentration-dependent cusps showing that the freezing process into an orientational glass state is a relaxational phenomenon.

Ferroelectricity and orientational glass behavior in the [Rbx(NH4)1−x]2SO4system

1996

Abstract The ordering in the electric dipole subsystem of the [Rbx(NH4)1−x]22SO4 family is investigated. The microscopic origin of ferroelectricity for x=0 is discussed, and evidences for the existence of orientational glass behavior in highly substituted crystals are presented.

Intramolecular Charge Transfer as Revealed by Results from the Measurement of Ground and Excited State Dipole Moments

1992

All-experimental values of self-quenching cross-sections for nf states (n=5-8) of potassium atoms

2007

All-experimental self-quenching cross-sections σ nf are reported for K(nf) states (n = 5, 6, 7, 8). The experiment was performed at varied temperatures of K vapour in a spectral cell. Time-resolved fluorescence was observed following pulsed step-wise excitation with dipole and quadrupole transitions K(4s) → K(4p) → K(nf). The values: σ 5f = 2.4 ± 1.7, σ 6f = 4.5±1.4, σ 7f = 8.1±1.8, and σ 8f = 18.2±3.0 (in units of 10−13 cm−1) were obtained from a Stern-Volmer-type plot.

Shear moduli of two dimensional binary glasses

2012

The shear moduli of two-component glasses in two dimensions are studied within mode coupling theory. Varying the concentration, strong mixing effects are observed along the glass transition lines for two interaction potentials. Nonoverlapping disks with size ratios between 0.3 and 0.9, and point particles interacting with (magnetic) dipoles of strength ratio between 0.1 and 0.6 are considered. Equilibrium structure factors (partially obtained from Monte Carlo simulations) and glass form factors, and perturbative calculations show that a softening of the elastic shear constant of glass upon adding another component arises from a dilution effect of the majority component. For very disparate m…

Use of the red-edge excitation effect for investigation of dielectric interactions in biomembranes

1999

Dipole moments of the fluorescent probes 1-phenylnaphthylamine (1-AN) and 1-anilinonaphthalene-8-sulfonate (1,8-ANS) are measured using electro-optical absorption and emission methods. Dipole moments in the ground and excited states were measured in cyclohexane and dioxane. It is shown that the charge distributions in the 1-AN and 1,8-ANS molecules differ substantially. The spectral dependence of the electro-optical coefficients suggests that the absorption spectrum of 1,8-ANS is due to a superposition of (at least two) electronic transitions. It is found that spectra of 1-AN in erythocyte ghosts are inhomogeneously broadened. The above effect makes it possible to selectively excite probe m…

Mutual capture of dipolar molecules at low and very low energies. II. Numerical study.

2011

The low-energy rate coefficients of capture of two identical dipolar polarizable rigid rotors in their lowest nonresonant (j(1) = 0 and j(2) = 0) and resonant (j(1) = 0, 1 and j(2) = 1, 0) states are calculated accurately within the close-coupling (CC) approach. The convergence of the quantum rate coefficients to their quantum-classical counterparts is studied. A comparison of the present accurate numerical with approximate analytical results (Nikitin, E. E.; Troe, J. J. Phys. Chem. A 2010, 114, 9762) indicates a good performance of the previous approach which was based on the interpolation between s-wave fly wheel quantal and all-wave classical adiabatic channel limits. The results obtaine…

A theoretical study on the regioselectivity of 1,3-dipolar cycloadditions using dft-based reactivity indexes

2004

The regioselectivity for a series of four 1,3-dipolar cycloaddition reactions has been studied using global and local reactivity indexes. The results of the theoretical analysis suggest that for asynchronous cycloadditions associated to polar processes, the regioselectivity is consistently explained by the most favorable two-center interactions between the highest nucleophilic and electrophilic sites of the reagents.

Dipolar NLO-phores with large off-diagonal components of the second-order polarizability tensor

1997

Triphenylmethyl and triphenylsilyl based molecular glasses for photonic applications

2015

Triphenylmethyl and triphenylsilyl structural fragments can be used to obtain glass forming, solution processable materials from polar chromophore molecules. Large number of compounds has been synthesized taking advantage of this approach, making it possible to identify some structure-property relations. Regarding the non-linear optical (NLO) properties of the given materials it is evident that triphenylmethyl groups help shielding unwanted NLO efficiency limiting dipolar interactions between polar chromophores in solid films. Chromophore stacking is still observed for compounds with large dipole momentum values. The glass transition temperatures of the compounds increase with the molecular…