High-resolution spectroscopy on the laser-cooling candidate La^{-}.

Area of Science:

• Atomic Physics
• Quantum Optics
• Spectroscopy

Background:

• Laser cooling has not been achieved for negative ions.
• Anion laser cooling could produce ultracold ensembles of any negatively charged species.
• The bound-bound transition in negative lanthanum (La-) was proposed for laser cooling.

Purpose of the Study:

• To investigate the proposed laser cooling transition in La-.
• To measure the transition frequency and resolve its hyperfine structure.
• To confirm La- as a candidate for anion laser cooling.

Main Methods:

• High-resolution laser spectroscopy on a beam of negative La ions.
• Analysis of the hyperfine structure transitions.
• Confirmation using multiconfigurational self-consistent field calculations.

Main Results:

• The center-of-gravity frequency of the 5d^{2}6s^{2} ^{3}F_{2}^{e} to 5d6s^{2}6p ^{3}D_{1}^{o} transition was measured at 96.592 80(10) THz.
• Seven of the nine expected hyperfine structure transitions were resolved and assigned.
• The determined hyperfine structure supports La- as a laser cooling candidate.

Conclusions:

• Negative lanthanum (La-) is a promising candidate for laser cooling.
• The identified transition requires only three laser beams for repumping all ground state hyperfine levels.
• This work paves the way for ultracold anion production.