Controlled preparation and vibrational excitation of single ultracold molecular hydrogen ions

Abstract

A single, trapped and ultracold molecular hydrogen ion is an attractive quantum system for exploring various aspects of fundamental physics, such as the determination of fundamental constants and testing their time-independence. Here we demonstrate, for the first time, controlled loading, sympathetic cooling, mass spectrometric identification, and vibrational excitation of ultracold single HD${}^{+}$ ions trapped in a tightly confining radiofrequency trap using single laser-cooled Be${}^{+}$ ions for sympathetic cooling. The apparatus can be used also for preparing other single ions, both lighter and heavier than the coolant ion.

GRAPHICAL ABSTRACT

Keywords:

• Single-ion trapping
• molecular spectroscopy
• sympathetic cooling
• molecular hydrogen ion

Acknowledgments

The authors are grateful to Prof. Johannes Hecker Denschlag's group (Universität Ulm) for providing their trap's CAD files. We are indebted to M. G. Hansen for his assistance on frequency stabilisation of the Doppler cooling laser, to S. Alighanbari for his help with the HD⁺ spectroscopy and photodissociation lasers, and to both for their insights and stimulating discussions. M.S., G.G. and C.W. acknowledge a fellowship from the Professor W. Behmenburg-Schenkung.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement number 786306, ‘PREMOL’), and from the Deutsche Forschungsgemeinschaft and Land Nordrhein-Westfalen in projects INST 208/667-1 FUGG and INST 208/737-1 FUGG. K. B. acknowledges support from the Alexander von Humboldt Foundation for a fellowship under Humboldt-ID 1159544.