Multi-photon absorption in mercury

Three-and four-photon resonant excitations of the mercury atom from its ground state have been observed and their dependence on the polarization of the incident light investigated. The energies of the nG states (n = 5 to 13) have been measured. In addition two photon excitation from the ground state to the 6³P states (J = 1 and 2) were observed. The pressure dependence of the relative signal sizes is briefly reported.