Sympathetic cooling of molecular ion motion to the ground state

Abstract

We demonstrate sympathetic sideband cooling of a ^40 CaH ^+ molecular ion co-trapped with a ^40 Ca ^+ atomic ion in a linear Paul trap. Both axial modes of the two-ion chain are simultaneously cooled to near the ground state of motion. The center of mass mode is cooled to an average quanta of harmonic motion ${{\bar{n}}_{{\rm COM}}}=0.13\pm 0.03$ , corresponding to a temperature of $12.47\pm 0.03\;\mu {\rm K}$ . The breathing mode is cooled to ${{\bar{n}}_{{\rm BM}}}=0.05\pm 0.02$ , corresponding to a temperature of $15.36\pm 0.01\;\mu {\rm K}$ .

Keywords

• molecular ions
• sympathetic cooling
• ground state cooling
• ultracold molecules
• laser cooling