Loading rate of Yb+ loaded through photoionization in radiofrequency ion trap

Abstract

We investigate the loading rate of Yb+ ions loaded through photoionization in a radiofrequency trap. The absolute or relative number of the loaded trapped ions is measured by use of an electric resonance of the secular motion. This method is applicable even in the presence of anharmonicity. In two-color photoionization, where the first-excitation laser drives the 1S0–1P1 transition in the Yb atom and the second one ionizes the atom from the 1P1 state, the loading rate is at its highest by the excitation of the ionization potential. A similar loading rate is observed at the second-laser wavelength around 369.5 nm, which is the wavelength for the cooling transition of Yb+. We estimate the loading cross section to be 40(15) Mb for the two-color excitation of the ionization potential. The excitation of the Yb atoms in the Rydberg states is detected by the enhancement of the loading rate. By irradiation with only the first-excitation laser, Yb+ is produced at a rate three orders of magnitude smaller than that when the non-resonant two-photon absorption from the 1P1 state is the dominant process. We also measure the charge-exchange rate between Yb+ and Yb, and discuss its effect on isotope-selective photoionization loading.