After the interaction of a xenon atom with two photons from an attosecond pulse (purple), the atom is ionized and multiple electrons (green balls) are ejected. This two-photon interaction is made possible by the latest achievements in attosecond technology.
B. Bergues, D. E. Rivas, M.Weidmann, A. A. Muschet, W. Helml, A. Guggenmoos, V. Pervak, U. Kleineberg, G. Marcus, R. Kienberger, D. Charalambidis, P. Tzallas, H. Schröder, F. Krausz, and L. Veisz
Optica, Vol. 5, Issue 3, pp. 237-242 (2018); DOI: 10.1364/OPTICA.5.000237