摘要
We report photoassociative spectroscopy of 88Sr2 in a magneto-optical trap operating on the 1S0→3P1 intercombination line at 689 nm. Photoassociative transitions are driven with a laser red detuned by 600–2400 MHz from the 1S0→1P1 atomic resonance at 461 nm. Photoassociation takes place at extremely large internuclear separation, and the photoassociative spectrum is strongly affected by relativistic retardation. A fit of the transition frequencies determines the 1P1 atomic lifetime (τ=5.22±0.03 ns) and resolves a discrepancy between experiment and recent theoretical calculations.