Solar particle data from the Kiel experiment on Helios 2 at 0.5 AU were compared with the predictions of a model which includes the effect of a postulated temporal profile of injection and which describes the coherent interplanetary transport of energetic particles. During an event on March 28, 1976, good agreement between observations and predictions was obtained for 5 MeV protons and for ~0.5 MeV electrons. For both species, this correspondence led to a mean free path of 0.7¿1 AU, independent of rigidity, and a focusing length of 0.86¿1 AU. The latter value is substantially larger than the value of ~0.25 AU, which is expected if the large-scale interplanetary magnetic field has its nominal spiral pattern. The large-scale dependence of scattering was investigated with the aid of a least squares criterion for agreement between the data and the model. The strongly anisotropic pitch angle distributions that were recorded throughout this nearly coherent event were most accurately described when the rate of scattering was assumed to go through a minimum centered at 90 ¿ pitch angle. Coherent interplanetary propagation and close proximity of Helios to the sun made it possible to derive reliable temporal profiles of particle injection at the coronal footpoint of the interplanetary field line through the spacecraft. Within the uncertainties, the injection of electrons had the same temporal dependence as the flux of 7-GHz radio noise had during the rising phase of the 'great burst' that accompanied the flare. After the radio maximum, the radio intensity decayed more rapidly than the electron injection. The injection of protons took place later and on a slower time scale than that of electrons.