Magnetically selected beams of atomic chlorine: measurement of long-range features of the chlorine–hydrogen and chlorine–methane potential-energy surfaces

An atomic beam of Cl (2PJ) atoms produced in a microwave discharge source in pure Cl2, after velocity and magnetic selection, has been used for absolute total cross-section measurements in collisions with the hydrogen and methane molecules. The data were obtained in the beam velocity range 0.4–2.3 km s–1(corresponding to 10–300 meV centre-of-mass energy) and under different populations of magnetic sublevels of Cl atoms. The analysis of the data, using an adiabatic decoupling scheme, permitted an accurate characterization of the long-range features for entrance valleys of the ground state and of the two lowest excited potential-energy surfaces. Non-adiabatic coupling matrix elements and other general features of the relevant interactions are also presented.