Absolute measurements of electron impact excitation cross-sections of atoms using cavity ringdown spectroscopy

• Cavity ringdown spectroscopy for electron impact excitation cross-sections.
• Measurements of absolute population densities of the energy levels.
• An analytical expression of electron impact excitation cross-section.
• The method is validated by two cases (the metastable Hg and the metastable Ne atoms).

A new method of using cavity ringdown spectroscopy (CRDS) technique to measure apparent electron impact excitation cross-sections (EIECS) for different energy levels of an atom is described. The method involves measurements of absolute population densities of the energy levels in concern using the high sensitivity CRDS, leading to an analytical expression of EIECS as a function of the population densities. Determination of EIECS in this method does not require an external calibration. The proposed method is validated by determining EIECS of the metastable levels of Hg (6s6p 3P0) and Ne (2p53s 3P2), and the results are in good agreement with the cross-sections reported in the literature. The population densities in both cases were extracted from the published data. This method exhibits promising potential for absolute measurements of EIECS of metastable energy levels.