Recent experimental ionization efficiency data (photoion signal as a function of laser intensity) for nonresonant two-photon ionization of Ag and Cu at λ = 248 nm show strong deviations from the expected laser intensity dependence of the nonresonant two-photon ionization process. In addition, the comparison of the ionization efficiency data of the photoions Ag+and Cu+shows drastic differences between silver and copper. These deviations are explained by considering a two-photon excitation process of the internal 4d (Ag) or 3d (Cu) electron followed by autoionization of the short-lived excited atomic states produced. In the case of Cu, the competition between the de-excitation due to autoionization processes and non-ionizing radiative de-excitation schemes must also be taken into account. The importance of these processes for quantitative surface analysis using secondary neutral mass spectrometry in combination with nonresonant two-photon postionization is addressed. © 1993.
Franzreb, K., & Fine, J. (1993). The significance of autoionization processes during nonresonant one-color two-photon ionization of neutral silver and copper atoms at λ = 248 nm. Nuclear Inst. and Methods in Physics Research, B, 83(1–2), 266–274. https://doi.org/10.1016/0168-583X(93)95937-Z