Electron excitation of the 2p state of atomic hydrogen near threshold

Abstract

The absolute total cross section for excitation of the 2p state of atomic hydrogen by electrons is examined in detail in the first electron volt above the 2p threshold. Only a single resonant state ('P) is found just above the threshold. An absolutevalue of the total 2p excitation cross section of 0*276_',4b"I," xuo2 at 11.0 eV is determined by calibration of the apparatus relative to the differential elastic scattering cross section value of 0.727 xaoa sr-' at 60" and 8.70 eV and by calibration of the Lyman alpha detector. These experimental measurements do not require any corrections for cascade radiation and do not depend upon any theoretical calculations for normalization. The present values agree well with the various three state close coupling calculations but disagree with the six-state close coupling calculations as well as all previous experimental values which were normalized to the Born approximation calculations.