Extended Data Fig. 1: Conceptual view of the arrangement used for high-resolution spectroscopy of HD+ using TICTES.
From: Precise test of quantum electrodynamics and determination of fundamental constants with HD+ ions
The spectroscopy wave (1.3 THz) crosses the ion cluster perpendicular to its long axis, enabling spectroscopy in the Lamb–Dicke regime. The ion cluster comprises atomic Be+ ions (blue dots) and HD+ molecular ions (red dots). The indicated laser beams implement the Doppler cooling of Be+ ions (313 nm), rotational cooling of HD+ (2.7 µm and 5.48 μm) and detection by REMPD (266 nm and 1.4 μm). The magnetic field B lifts the degeneracy of Zeeman sublevels during terahertz spectroscopy. The polarizer and the half-wave plate enable adjustment of the polarization and intensity of the terahertz radiation.
