Cooling of a Zero-Nuclear-Spin Molecular Ion to a Selected Rotational State

Abstract

We demonstrate rotational cooling of the silicon monoxide cation via optical pumping by a spectrally filtered broadband laser. Compared with diatomic hydrides, SiO\+ is more challenging to cool because of its smaller rotational interval. However, the rotational level spacing and large dipole moment of SiO\+ allows direct manipulation by microwaves, and the absence of hyperfine structure in its dominant isotopologue greatly reduces demands for pure quantum state preparation. These features make ${}^{28}$Si${}^{16}$O\+ a good candidate for future applications such as quantum information processing. Cooling to the ground rotational state is achieved on a 100 ms time scale and attains a population of 94(3)\%, with an equivalent temperature $T=0.53(6)$ K. We also describe a novel spectral-filtering approach to cool into arbitrary rotational states and use it to demonstrate a narrow rotational population distribution ($N\pm 1$) around a selected state.

6+2 pages, 4+1 figures; latest version includes supplemental materials

References in corpus (4)

• A High Phase-Space-Density Gas of Polar Molecules
• Optical pumping and vibrational cooling of molecules
• Rotation of quantum impurities in the presence of a many-body environment
• Challenges of laser-cooling molecular ions

Cited by in corpus (13)

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• Æ codes
• Precisely Spun Super Rotors
• Laserless quantum gates for electric dipoles in thermal motion
• Enhancing reactivity of SiO${}^{+}$ ions by controlled excitation to extreme rotational states
• Electroweak Nuclear Properties from Single Molecular Ions in a Penning Trap
• High-resolution laser-induced fluorescence spectroscopy of ${}^{28}$Si${}^{16}$O${}^{+}$ and ${}^{29}$Si${}^{16}$O${}^{+}$ in a cryogenic buffer-gas cell
• Radium-containing molecular cations amenable for laser cooling
• Photon spin molasses for laser cooling molecular rotation
• Features of Molecular Structure Beneficial for Optical Pumping