Axial distributions of plasma and floating potentials, electron number density and
the electron energy distribution function (EEDF) have been measured in the double
layer (DL) region of an He discharge constriction. Excitation processes in the
constriction region are studied. Using a linearization method for the nonstationary
balance equations and choosing appropriate discharge conditions, the step excitation
rate by electron impact for the 2 S 3 D transition in He is determined