CRESU Ecoulement Supersonique

CRESU Cinetique de reaction en ecoulement supersonique uniforme... 

In this chapter, we describe the current status of theoretical kinetics for chemical reactions at low temperature, i.e., from 1 to 200K. The desire to understand the chemistry of interstellar space and of low temperature planetary atmospheres provides the general motivation for studying chemical kinetics at such temperatures. For example, the chemistry of Titan s atmosphere is currently a topic of considerable interest. This motivation led to the development of novel experimental techniques, such as the CRESU (cinetique de reaction en ecoulement supersonique uniforme) method, which allows for the measurement of rate coefficients at temperatures as low as lOK (see Chapter 2 by Canosa et ai). Such measurements provide important tests for theory and have sparked a renewed interest in theoretical analyses for this temperature range. ... 

Significantly lower temperatures have been achieved by Rowe and co-workers [23, 24] using the CRESU (Cinetique de Reaction en Ecoulement Supersonique Uniforme) technique, in which the gas is expanded through a Laval nozzle and the flow parameters, density, temperature, pressure and velocity in the central 10-20 mm of the resulting uniform supersonic jet are invariant in both axial and radial directions, since the flow is isentropic over a flow distance of tens of centimetres. The jet crosses an electron beam to provide the ions and into a mass spectrometer, which is movable so that the reaction times can be varied. Measurements have been made down to 8 K. Measurements on He + N2 gave... 

Fig. 3.3 Sketch of a CRESU (Cinetique de Reaction en Ecoulement Supersonique Uniforme) apparatus configured for the study of radical-neutral reactions. In this arrangement, radicals are generated by photolysis of a suitable precursor using radiation from a fixed-frequency pulsed laser operating at one of the three wavelengths, 226, 248, or 193 nm, and are detected by laser-induced fluorescence excited by tuneable radiation from a dye laser or a master oscillator parametric oscillator (MOPO) [56]...

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