Absolute cross sections for electron impact excitation of mercury 61P1 at 15, 60 and 100 eV

Abstract

Absolute differential and angle-integrated cross sections together with generalised oscillator strengths for the 61S0 to 61P1 excitation of mercury by electron impact have been measured. The incident electron energies were 15, 60 and 100 eV and the scattering angles varied from 4' to 135'. The authors used the method of the static gas target which yields absolute values of sigma ( theta ) by measuring the ratio of the scattered and primary currents, the target density (via pressure and temperature measurement) and the scattering geometry. A suitable extrapolation to zero target density yields values without disturbing effects. Because of the rather low intensity of the monochromatic beam absolute values of sigma ( theta ) could be measured directly only at small scattering angles. At larger angles the authors used a channel electron multiplier as the detecting device. Its efficiency could be determined in the range of overlap with the help of the absolute data. The results demonstrate the inadequacy of DWBA theories for predicting cross sections at the lower incident energy (15 eV); but at higher energies (60 and 100 eV) the agreement is satisfactory.