Electron Excitation Functions of Mercury

Absolute excitation functions of some 40 transitions of the mercury atom have been measured. As in the case of helium, the excitation functions of the singlet states have the common feature of a broad maximum around 30 eV, whereas the triplet states show the characteristic sharp peaks at lower voltages. The excitation functions of the lower states exhibit fine structure near the threshold, which may be attributed to cascade from the states of higher energies. The cascading effect has been examined for the excitation of the 7¹S₀, 7³S₁, 7³P₂, 6³D₃, and 6³D₂ states. At 15 eV the cascade corrections are small for 7³P₂, 6³D₃, and 6³D₂, but amount to approximately 42% for 7¹S₀. The major source of population of the 7³S₁ state is found to be cascade transitions from the 7³P₂ state rather than direct excitation. Direct-excitation cross sections of the 7¹S₀, 6³D₂, 6³D₃, and 7³P₂ states at 15 eV have been determined and the results are compared with the theoretical calculations.