Coordinator: Wolf D. Geppert, Stockholm University
To date most laboratory chemistry has been performed under terrestrial conditions under standard conditions (room temperature and air pressure) and overall focused on reactions between closed shell molecules. However, since radical-induced processes have found to be important in higher layers of Earth’s atmosphere (ozone depletion) and ion reaction play a crucial role in natural and man-made plasmas (fusion reactors, combustion processes), interest in these processes has increased considerably during the last decades. However, few of the studies of radical- and ion-induced reactions have been carried out at the low pressures and temperatures prevalent in the interstellar medium or higher layers of planetary atmospheres.
Low-temperature chemical processes can usefully be divided into those with and without barriers. Reactions without barriers quickly become statistical and are conventionally described by capture theories. Reactions with barriers might be expected to become very slow at low temperatures, but in several cases substantial tunneling rates persist even in the low temperature limit. In particular, long-range potential wells exist in the entrance and exit channels of many reactions; such wells dramatically decrease tunneling path lengths and increase tunneling rates. Developing our knowledge of the quantum nature of interactions/reactions is therefore essential to modeling such barrierless reactions and deriving rate constants which can be directly measured and tested in the laboratory.
However, many of the radical and ion-induced reactions involving or leading to more complex species involve very complicated potential surfaces that are difficult to calculate. In many cases one has therefore to resort to experimental studies in order to gauge the rate constants and branching ratios of these processes, which are often difficult to predict and have proven counter-intuitive. A multitude of methods have been developed to this end: crossed-beam and supersonic flows have been successfully applied to investigate radical-neutral reactions, ion traps have been successful in studies off ion-neutral reactions and flowing afterglow machines and ion storage rings have been employed for ion-electron reactions. Data obtained through the research efforts have served as input for improved state of the art model calculations of different
The aims of the working groups will be:
- To serve as an interdisciplinary forum for astronomers, experimentalists, modelers and theoreticians interested in the investigations of astrochemicaly relevant radical- and ion induced reactions
- To identify crucial radical and ion-induced processes to be preferentially investigated
- To develop and improve experimental and theoretical methods to investigate these reactions
To obtain information about the group members, please check the members webpage.
If you want to join this working group, please contact the coordinator Wolf D. Geppert, Stockholm University, phone: 0046-8-55378649, e-mail: wgeppert [at] hotmail [dot] com
