Charge relaxation rate

Within the RBeij series the IV CeBeij with its valence of 3.04 (Wohlleben and Rohler 1984a) has received a lot of attention. Due to its nearly integral valence rather large charge relaxation rates have been conjectured for this compound... 

Fig. 40. (a) Temperature dependence of the longitudinal acoustic-phonon frequencies of Smo Y jsS in the [111] direction for four different values of the wavevector q (see Mook et al. 1981). (b) Temperature dependence of the bulk modulus Cg of Sm Y 25S measured by Bril-iouin scattering. Cg continues to soften upon cooling below 200 K, uniike the behavior of the phonon mode frequencies for qaO.l (flg. 40a). (c) Temperature dependence of the charge relaxation rate derived from the experimental data in figs. 40a and 40b (open circles) and calculated from theory (Schmidt and Miiller-Hartmann 1985) (solid line). The theoretical curve has been matched at 300 K to the experimental value. 

Fig. 44. Schematic representation of the influence of different charge relaxation rates of IV rare-earth ions on the frequencies of the optical phonon modes (e.g., (dj and at ) and on the q=0 longitudinal acoustic-phonon modes, represented by the bulk modulus Cg (see text). For the stable n - and (n -1- l) -valent rare-earth compounds we show generalized reference lines. Four typical cases are shown with the representative samples given at the bottom.

Experimentally determined charge relaxation rates at room temperature compared to the theoretical values (Muller-Hartmann 1981), which have been scaled by the measured spin relaxation rates References for the values of and the valence have been summarized by Zirngiebl (1986) and by Zimgiebl and Guntherodt (1990). ( A means corresponds to .)... 

Unlike the lanthanides, the actinides U, Np, Pu, and Am have a tendency to form linear actinyl dioxo cations with formula MeO and/or Me02. All these ions are paramagnetic except UO and they all have a non-spherical distribution of their unpaired electronic spins. Hence their electronic relaxation rates are expected to be very fast and their relaxivities, quite low. However, two ions, namely NpO and PuOl", stand out because of their unusual relaxation properties. This chapter will be essentially devoted to these ions that are both 5/. Some comments will be included later about UOi (5/°) and NpOi (5/ ). One should note here that there is some confusion in the literature about the nomenclature of the actinyl cations. The yl ending of plutonyl is often used indiscriminately for PuO and PuOl and the name neptunyl is applied to both NpO and NpOi. For instance, SciFinder Scholar" makes no difference between yl compounds in different oxidation states. Here, the names neptunyl and plutonyl designate two ions of the same 5f electronic structure but of different electric charge and... 

In electrode kinetics, however, the charge transfer rate coefficient can be externally varied over many orders of magnitude through the electrode potential and kd can be controlled by means of hydrodynamic electrodes so separation of /eapp and kd can be achieved. Experiments under high mass transport rate at electrodes are the analogous to relaxation methods such as the stop flow method for the study of reactions in solution. 

Note that the investment cost of each distillation column can be expressed as a nonlinear fixed charge relaxation in which the nonlinearities are introduced due to the cost dependence on both the temperature and the column and the feed flow rate. 

Mg(DOPMR)2-H2(DOP) [Mg(DOP )+-(R)2-[H2(DOP )] - Solvent acetone, CH2C12, DMF or alkyl-acetates X, = 532 or 588 nm the charge-recombination rate constant correlates with the reverse of the solvent relaxation times [196]... 

The rates of the exchange reactions between several complexes Ln(DTPA)2 (Ln = La, Nd, Gd, Ho and Lu) and Eu3+ have been studied by spectrophotometry on the charge-transfer band of Eu3+ [20, 31]. Similar studies were carried out with the Gd3+ complexes of some other DTPA derivatives DTPA-BMA,DTPA-N-MA and DTPA-N -MA. The progress of the exchange reactions between the complexes and Eu3+ and Cu2+ was followed by spectrophotometry, while when Zn2+ was used as exchanging ion, the longitudinal relaxation rates of water pro-... 

Fig. 9. A rotation spectrum is produced by observing the motion of a cell in a rotating electric field of constant amplitude and plotting the rotation speed of the cell against frequency of the field. In solutions of low conductivity, the cell rotates in the opposite direction to the field (anti-field rotation) at low frequencies. This rotation reaches a peak when the field frequency corresponds to the charge relaxation time of the membrane. The position of this peak therefore contains information about membrane permittivity and conductivity. As the frequency increases further, the rate of cell spinning falls, becoming zero at about 1 MHz. Above this frequency, the cell starts to spin with the field (co-field rotation) and a second peak is reached. The frequency at which this peak occurs depends in practice mainly on the conductivity of the interior of the cell. It may be used for non-destructive determination of cytosolic electrolyte concentration.

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