Photoabsorption Spectrum and Optically Forbidden Transitions of Krypton by Electron Impact

A high resolution fast electron energy loss spectrometer with
multi-channel energy analyse was employed. The maxima just above the threshold 4^-1(²P_1/2), which is regarded as a shape resonance, was obtained at 16.3 eV. The optically forbidden excitations of 4s electron were measured for the first time, and the energy positions are 23.75 eV(4s^-15s), 25.66 eV(4^-16s/4d) and 26.60 eV(4^-17s/5d), respectively.