VIBRATIONALLY RESOLVED INELASTIC-SCATTERING AND CHARGE-TRANSFER IN H-C2H4 COLLISIONS()

Differential cross sections and time-of-flight spectra have been measu red in a crossed molecular beam apparatus for inelastic scattering and charge transfer in collisions of 30 eV protons with ethylene. High re solution inelastic time-of-flight spectra reveal peaks corresponding t o the fundamentals of at least two of the infrared active antisymmetri c vibrational modes of ethylene. In the time-of-flight spectra of H at oms resulting from charge transfer energy loss, peaks corresponding to excitation of two electronic states of the ethylene molecular ion are resolved. The H-atom product angular distributions are consistent wit h a 2.0 eV potential well in the ground state potential energy surface of the charge transfer reaction. The observations for the antisymmetr ic vibrational modes are explained in terms of an ion-induced dipole m echanism. Excitation of the symmetric modes is attributed to a vibroni c coupling mechanism. An appendix provides a detailed account of the v ibronic distributions in idealized low energy, high symmetry collision s leading to stable C2H5+ complexes.