Bromine relaxation

Studies of the dependence of on radiofrequency field strength have been demonstrated by Morgan and Strange (e.g. Ref. 149]) to be an efficient method of obtaining chlorine and bromine relaxation times. From plots like that pictured in Fig. 2.4 the halogen relaxation time is obtained through the ratio of slope to intercept. One difficulty in these types of experiments is that for bromine and chlorine two halogen isotopes contribute to the scalar relaxation. In some cases... 

Systematic studies of the concentration dependence of Br and I relaxation in aqueous solutions of alkaline earth bromides and iodides were reported by Hertz [237] and later the bromine relaxation of aqueous alkaline earth bromide solutions was investigated by Richards and co-workers [51 52], In comparison with the alkali ions, these divalent ions cause a considerably stronger increase in halide ion relaxation rate with concentration. The shape of the plots of relaxation rate versus concentration resembles that obtained with the smaller alkali ions. The different alkaline earth ions have similar influence on Br and I relaxation. The sequence of increasing effect on Br relaxation... 

This result shows than the initially added trichloromethyl group has little influence on the stereochemistry of the subsequent bromine atom-abstraction. The intermediate 2-(trichlor-omethyl)cyclohexyl radical presumably relaxes to the equatorial conformation faster than bromine-atom abstraction occurs. In contrast with addition to A -octahydronaphthalene, the addition is exclusively /ran -diaxial ... 

Aiken, F. Cox, B. G. Sorensen, P. E. Proton transfer from carbon. A study of the acid-base-catalyzed relaxation and the bromination of aryl-substituted methanedisulfones./. 

Crystal structures for some iodine-substituted compounds were selected from the CSD according to the same criteria applied for chlorine and bromine compounds, except that the number of iodine atoms [criterion (a)] was relaxed to > 1. This search resulted in 18 observations for C(sp3)—I bonds with a mean value of 216.6 pm and o = 2.0 pm. The individual values range from 212.3 to 220.6 pm. 34 observations were listed for C(sp2)—I distances with a mean value of 210.1 pm and a large standard deviation of 6.1 pm. The values range from 205.7 to 223.9 pm. The mean values of this sample are very close to the typical bond distances listed by Allen and Coworkers172. Table 46 lists C(sp3)—I and C(sp2)—I bond distances for some selected crystal structures. 

Proton 1/Ti of heavily doped polyacetylene films with different dopants such as FSO3H, FICIO4, iodine, bromine and potassium was measured by Shimizu et al.113 and the behaviour expected for a quasi-ID metal was not found. Some of them showed a time dependence of 1/Ti. They have deduced the temperature dependence of resistivity from the 1/Ti and 1/Ti versus temperature shows T1 5 behaviour above 40 K and deviates from such behaviour below 40 K. Mizoguchi and Kuroda107 have given a comprehensive review of many investigations of NMR relaxation of both 1FI and 13C in undoped polyacetylene. 

Fig. 2. Schematic representation of the mechanism of photostimulated luminescence in BaBrF Eu. (A) Formation of a colour centre (F) under X-ray irradiation by trapping of an electron in a bromine vacancy with trapping of the hole formed in the valence band by a hole trapping centre (HT) in the vicinity (B) Release of the trapped electron by laser irradiation and transfer of the electron-hole recombination energy to Eu2+. Relaxations after electron transfers have not been represented.

Collision-induced vibrational excitation and relaxation by the bath molecules are the fundamental processes that characterize dissociation and recombination at low bath densities. The close relationship between the frequency-dep>endent friction and vibrational relaxation is discussed in Section V A. The frequency-dependent collisional friction of Section III C is used to estimate the average energy transfer jjer collision, and this is compared with the results from one-dimensional simulations for the Morse potential in Section V B. A comparison with molecular dynamics simulations of iodine in thermal equilibrium with a bath of argon atoms is carried out in Section V C. The nonequilibrium situation of a diatomic poised near the dissociation limit is studied in Section VD where comparisons of the stochastic model with molecular dynamics simulations of bromine in argon are made. The role of solvent packing and hydrodynamic contributions to vibrational relaxation are also studied in this section. 

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