Efficient ground-state cooling of an ion in a large room-temperature linear Paul trap with a sub-Hertz heating rate

We demonstrate efficient resolved sideband laser cooling (99±1% ground-state population) of a single ⁴⁰Ca⁺ ion in a large linear Paul trap (electrode spacing of 7 mm) operated at an rf drive frequency of just 3.7 MHz. For ion oscillation frequencies in the range 280--585 kHz, heating rates below or about one motional quantum per second have been measured at room temperature. The results, obtained under these unconventional sideband cooling conditions, pave the way for a range of new types of cold ion experiments, including spectroscopy of molecular ions as well as ultracold chemistry.