M23-region x-ray emission spectrum from gaseous krypton

The $M_{2,3}$ x-ray emission spectrum of gaseous krypton excited by direct electron bombardment has been recorded with a scanning single-flat crystal spectrometer. The most prominent spectral features are two peaks at 187 and 203 eV, with the 187-eV peak having an extended low-energy tail. This low-energy tail is attributed to double-electron single-vacancy transitions owing to the strong mixing of the final-state configuration $4s4{p}^{6}^{2}S$ with the even levels 4s²4p⁴ns²S and 4s²4p⁴nd²S. The 203-eV peak is identified as probably the single-electron double-vacancy $M_{2,3}{M}_{2,3}\to M_{2,3}{N}_1$ multiplet complex.