Temperature jump method monitoring chemical relaxation

Perturbation or relaxation techniques are applied to chemical reaction systems with a well-defined equilibrium. An instantaneous change of one or several state fiinctions causes the system to relax into its new equilibrium [29]. In gas-phase kmetics, the perturbations typically exploit the temperature (r-jump) and pressure (P-jump) dependence of chemical equilibria [6]. The relaxation kinetics are monitored by spectroscopic methods. 

Relaxation methods can be classified as either transient or stationary (Bernasconi, 1986). The former include pressure and temperature jump (p-jump and t-jump, respectively), and electric field pulse. With these methods, the equilibrium is perturbed and the relaxation time is monitored using some physical measurement such as conductivity. Examples of stationary relaxation methods are ultrasonic and certain electric field methods. Here, the reaction system is perturbed using a sound wave, which creates temperature and pressure changes or an oscillating electric field. Chemical relaxation can then be determined by analyzing absorbed energy (acous-... 

Whenever a chemical equilibrium is subjected to a perturbation, most commonly a change in temperature, pressure, pH, or other concentrations, the system will start to relax back to a new equilibrium state. The kinetics of this relaxation can be followed. Methods for quickly inducing a perturbation followed by monitoring the relaxation are referred to as jump techniques. Changes in temperature, pH, and pressure can often be done fast enough that reactions with half-lives in the microsecond range can be followed. For example, the equilibrium positions of Bransted acid-base reactions are controlled by the pH, and therefore pH jump experiments are particularly useful with these reactions. 

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