Advances in Molecular Relaxation Processes最新文献

The rates of absorption (solubilization) of positively charged acridine (and related) dyes into anionic micelles formed by sodium n-alkyl sulphates

The mechanism proposed for incorporation of dye into the micelle is a two-step process involving a very rapid (diffusion-controlled) adsorption of dye

Below the critical micelle concentration (CMC) of the surfactant, a time-dependent association of dye and surfactant is observed, which gives large agg

CNDO/2 molecular orbital calculations have been carried out on the hydrogen bonding of water and HF with the π-electrons of HCN, CH₃CN, C₂H₄, C₂H₂ and H₂CO. The dissociation energies of hydrogen bonds with the π-electrons of the triple bond are higher than those with the double bond in H₂CO. In the case of the interaction of water with HCN and CH₃CN, the hydrogen bond energies with the lone pairs and π-electrons are about the same. For the interaction of HF with a nitrile and an isonitrile, the dissociation energies are comparable.

The auto-correlation function Φ_h,h(r) of the relaxation time distribution function h(r) is obtained from the auto- and cross-correlations of real and imaginary parts of the permittivity by inversion of convolution integrals. If the permittivity data are subject to experimental error, the spectrum of the auto-correlation Φ_h,h(r) appears to be most suitable for the determination of the main characteristics of the distribution function h(r). It is necessary to obtain additional information by evaluating the lower order moments of the distribution function.

A theoretical study by STO—3G method of the hydrogen bond association between acetonitrile and phenol is reported. The results are compared to those previously obtained by static dielectric constant measures and CNDO/2 calculations.

The latter two methods, experimental and theoretical, have made possible a comparative study of propionitrile—, fumarodinitrile— and succinonitrile—phenol complexes.

The barriers to internal rotation in the isolated succinonitrile molecule are determined. In addition to the trans conformation, there is a stable gauche conformation, the existence of which appears to be more probable with the formation of the hydrogen bond.

The dielectric relaxation of Br(CH₂)_N−1Br, with N = 4 and N = 5, of Br(CH₂)_N−1Br with N = 3 and N = 4 and for 1,2-dichloroethane is deduced using the Jernigan method, where the internal conformational changes are governed by the rotational isomeric state model of Flory. It is found that the dipole moment correlation function for internal conformational changes depends upon the choice of reference coordinate system, and that the dipole moment correlation function cannot be generalized so as to include both overall and internal motions of the chain. An alternative approach, which involves the rotational isomeric state model but conserves angular momentum during an elementary conformational change, is suggested. The available microwave dielectric data on such compounds are considered in relation to the results of the theory.

The dielectric absorption of liquid n-alkanes has been investigated as a function of frequency and temperature by means of interferometric and resonator techniques in the microwave range and Fourier spectrophotometry in the far infrared band. The large amount of permittivity data now available in a wide frequency range (9 to 6000 GHz) permits a satisfactory evaluation of relaxation parameters. The obtained dielectric principal relaxation times (1.6 ps for n-pentane to 8.8 ps for n-dodecane at room temperature) have been compared with other characteristic times taken from the literature for n-alkanes and cognate aliphatic chains. The absorption in the microwave range is possibly caused either by a reorientational relaxation process of weak permanent dipoles attached to the molecule ends or by a translational relaxation process of temporary dipoles induced in the molecule by the local electric field evoked by surrounding neighbours. An estimation shows that, in the latter case, dipole moments are generated which are of amounts comparable with the measured values (about 0.07 D at room temperature), and the lifetimes of which are given by the measured dielectric relaxation time.

These dihydrates are halogenometallates of dioxonium. Their infrared and Raman spectra show that the central hydrogen bond is short and centered with a single minimum (isotopic effect). δ and γ OH vibration of that bond are very close, showing a very weak interaction with terminal H₂O groups. Furthermore, terminal vOH show that H₅O₂⁺ is quite free, with a greater liberty in the hexachloroantimonate.

Proton relaxation times of dimethylsulfoxide containing 10⁻²–10⁻¹ M manganese (II) perchlorate are measured at two frequencies, 8 and 60 MHz, and sixteen temperatures (20–165 °C). These data allow us to compute: the contact shift Δω_M = 748 ± 13 Hz (25 °C and 60 MHz); the hyperfine coupling constant; the kinetic parameters for the exchange: bound DMSO

Conduction electron spin resonance (CESR) spectra are reported for colloidal alkali metal particles in frozen solutions of sodium and potassium in hexa

Electron spin—lattice relaxation rates are governed primarily by spin—orbit coupling during spin—phonon scattering of high velocity electrons, an resistivity.

A novel method of isolating the spin—orbit contribution to spin relaxation at 1.3 K is described: there is no evidence for freezing in of Umklapp pro