TECHNIQUES FOR THE STUDY OF REACTION-KINETICS AT LOW-TEMPERATURES - APPLICATION TO THE ATMOSPHERIC CHEMISTRY OF TITAN

Data on the low-temperature (< 200 K) dependence of the kinetics of ch emical reactions are of great importance for understanding the composi tion of planetary atmospheres (as well as interstellar clouds). To dat e such studies have been relatively rare but the situation is beginnin g to change. During the past 10 years a number of experimental instrum ents have been designed to address this problem. These instruments rel y on either cryogenic or supersonic cooling, and both methods have bee n applied to the study of neutral-neutral or ion-neutral reactions. We briefly review these different techniques, with an emphasis on the CR ESU method, and provide examples of the types of reactive systems that have been studied, with particular attention to those relevant to the atmosphere of Titan. The perspectives for future work are also evoked .