CRESU experiment - Definition and Overview

The CRESU experiment (meaning Cinétique de Réaction en Ecoulement Supersonique Uniforme, or Reaction Kinetics in Uniform Supersonic Flow) is an experiment investigating chemical reactions taking place at very low temperatures.

This is achieved by expanding a mixture of NCNO and a molecular reactant through a nozzle resulting in a supersonic flow of the gas. This is necessary so that the gas is cooled down to an extremely low temperature, but before it has time to condense into a solid. The NCNO is broken down by a pulsed laser in to CN and NO radicals, of which the CN reacts with the molecular reactant. The rate of reaction is measured using a laser pulse to detect the fluorescence signal - which falls after reaction. The CRESU apparatus has been used to simulate the conditions in interstellar clouds, making us able to perform chemical reactions under conditions very similar to these clouds. Surprisingly, reactions occurred which would have been unexpected under these harsh conditions. This would explain the occurrence of large molecules obsevered in interstellar clouds.

External links:

• http://web.bham.ac.uk/i.r.sims/irsims/sims_res04.html - the Birmingham CRESU site