The reaction C(P-3(J)) + C2H4(X(1)A(1)) --> C3H3 + H(S-2(1/2)) has been studied using complementary crossed molecular beam techniques. Integral cross sections have been obtained in the range of relative translational energies E-T = 0.49-24.9 kJ mol(-1) in experiments conducted with pulsed supersonic beams coupled with laser-induced fluorescence detection of H(S-2(1/2)) atoms. The major reaction pathway leading to HCCCH2 (propargyl) + H has been found without any barrier, with relative integral cross sections that are proportional to (E-T)(-0.60+/-0.03) below 8 kJ mol(-1). Threshold for a minor pathway, leading also to H formation, occurs around 6 kJ mol(-1); the relative importance of this second pathway increases with relative translational energy. Differential cross sections have been obtained at three relative translational energies: E-T = 9.1, 17.2, and 30.8 kJ mol(-1) in experiments conducted with continuous supersonic molecular beams coupled with universal mass spectrometric detection and time-of-flight analysis. At the lowest E-T of 9.1 kJ mol(-1) formation of HCCCH2 (propargyl) + H is observed to be the dominant channel with a nearly forward-backward symmetric angular distribution in the center-of-mass (cm) frame; about 35% of the total available energy is channeled into translation indicating that the propargyl radical is highly internally excited; formation of less stable C3H3 isomer(s) is minor (2%). As E-T increases, formation of appreciable, increasingly larger fractions of less stable propyn-1-yl and/or cyclopropenyl isomers is also observed. These findings are consistent with the integral cross-section measurements. While formation of propargyl is thought to proceed via an osculating complex mechanism following addition of C(P-3(J)) to the double bond of ethylene, the dynamics of formation of the less stable isomers is going through a long-lived complex, as witnessed by an isotropic cm angular distribution. The H-2 elimination channel leading to C3H2 formation has not been found to occur, which suggests that inter-system-crossing to the ground singlet C3H4 potential energy surface manifold has low probability and/or the H-2-elimination process on the triplet surface is characterized by a very large exit potential barrier. (C) 2003 American Institute of Physics.