Simultaneously Forbidden Resonances and Ion Cooling

Zoran Andelkovic, Radu Cazan, W. Nörtershäuser +7 more

We have performed laser cooling of Mg${}^{+}$ ions confined in a Penning trap. The externally produced ions were captured in flight, stored, and laser cooled. Laser-induced fluorescence was observed perpendicular to the cooling laser axis. Optical detection down to the single-ion level together with the electronic detection of the ion oscillations inside the Penning trap have been used to acquire information on the ion storage time, ion number, and ion temperature. Evidence for the formation of ion crystals has been observed. These investigations are an important prerequisite for the sympathetic cooling of simultaneously stored highly charged ions and the precision laser spectroscopy of forbidden transitions in these.

P. E. Toschek

K. Ravi

P. E. Toschek

An ion, or atom, confined in a ‘trap’ and laser-irradiated on its resonance line generates a quasi-continuous flow of scattered light, and makes the line split or shifted. When the ion is probe-laser excited, on a neighbouring dipole-forbidden line to a metastable state, the flow subsides. Also, the shift or dynamic Stark splitting of the resonance and of the dipole-forbidden line vanishes. De-excitation of the ion requires the probe laser to be re-tuned to the unshifted resonance. Cyclic scanning of this laser shows a mean frequency offset of the on-off jumps from the off-on jumps. This random hysteresis may cool or heat the ion, and lock an ensemble in the metastable state.

Alex Retzker, Martin Bodo Plenio

In this work we present a solution to this problem that relies on the fast Stark shift gate. In this scheme off-resonant carrier transitions that would lead to heating are forbidden thus achieving lower final temperature and a much higher cooling rate.

Manas Mukherjee