Studies of reactions relevant to astrochemistry

We review experimental studies of bimolecular exchange reactions between neutral species that can occur in dense molecular clouds: kinetics experiments performed with the so-called CRESU technique which measure global reaction rates and dynamics measurements performed with crossed molecular beam apparatuses which bring information on the products and branching ratios. Special attention is devoted to reactions of the carbon atom which may contribute to the synthesis of long polyyne or polyene chains. Results on the reactions of C(3PJ) atoms with methylacetylene, allene, ethylene and acetylene, with CRESU (in terms of rate coefficients) and crossed-beam experiments (in terms of integral and differential reaction cross sections) are discussed. Emphasis is placed on the interest to use these complementary methods in conjunction to obtain detailed rate coefficients. It is also shown that crossed-beam experiments can furnish sensitive tests to the state-to-state cross sections and rates for rotational energy transfer by inelastic collisions obtained by theoretical methods, as exemplified with CO + H2 collisions.