Precision spectroscopy of Mg atoms in a magneto-optical trap

We report the results of experimental investigations aimed at creation of the optical frequency standard based on magnesium atoms cooled and localised in a magneto-optical trap (MOT). An experimentally realised MOT for magnesium made it possible to obtain a cloud comprising ~10⁶ – 10⁷ atoms at a temperature of 3 – 5 mK. The results of ultra-high resolution spectroscopy of intercombination ¹S₀ – ³P₁ transition for Mg atom are presented, the resonances in time-domain separated optical fields with the half-width of Γ = 500 Hz are recorded, which corresponds to the Q-factor of the reference line Q = ν/Δν ~1.3 × 10¹².