DIFFERENTIAL TRANSLATION ENERGY-LOSS DISTRIBUTIONS AT 1-EV ENERGIES - K-C2H2

In K-C2H2 collisions at collision energies 0.4 less-than-or-similar-to E less-than-or-similar-to 1.3 eV and scattering angles 40-degrees less-than-or-similar-to curly theta less-than-or-similar-to 180-degrees surprisingly little transfer of energy from translation into the internal degrees of freedom of the acetylene molecule is found. The observations are consistent with the assumptions of electronically covalent encounters, insignificant activation of the acetylene vibrations, and rotational excitation produced by spindle-shaped equipotentials, nearly spherical in a broad vicinity of the C = C bond.