Practice of Kinetics (Comprehensive Chemical Kinetics, Volume 1)

138 EXPERIMENTAL METHODS FOR FAST REACTIONSlog W TFig. 10. Real (ZrC) and imaginary (Z*,,,) parts of the transfer function.frequency o is shown in Fig. lO(a). The relaxation time z may be readily measuredfrom ;I curve of this form; it corresponds to the value of o at which Gre has the maximumslope. A physical quantity which, for a relaxing system, shows a frequencydependence of this type is the sound velocity. This frequency dependence is calledsound dispersion, and consequently the methods which follow the frequency behaviourof Grc are called dispersion methods.The imaginary part of the transfer function Zim has a frequency dependence shownin Fig. 10(b). It represents the amaunt ofenergy transferred to the system per periodof oscillation owing to the relaxation, and the relaxation time correspmds to thefrequency at which the greatest interaction OCCLI~S. Again, the eKect on sound waveshas been widely used. Methods nial