Practice of Kinetics (Comprehensive Chemical Kinetics, Volume 1)

140 EXPERIMENTAL METHODS FOR FAST REACTIONSIIlog(*)Residua Iabsorptionlog 0 -Fig. 1 I . Variation of (or/w2) with w for a system possessing two chemical relaxation times.the highly hydrogen-bonded water structure. Also, a relaxation effect which is toofast to be picked up as a distinct “step” will contribute to ares. The most satisfactoryway to separate ache”, from a,,, whenever possible is to take measurements overthe whole frequency range for which ache”, is important.Another term which is sometimes used is the chemical absorption cross-section,Q, defined as(NA = Avogadro’s Number, co = concentration of species i in m~le.cm-~). Aplot of log [Qh](h = sound wavelength) against log o has the form shown in Fig. 12(cf Fig. 10(b)), where the inaxima represent the relaxation times (omax z l/~).A function which gives the same type of plot against log o is the coefficient of ab-Fig. 12. Variation of (QPJlog w -with w for a system possessing two chemical relaxation times.