Frequency of the ultranarrow ¹S₀ - ³P₂ transition in ⁸⁷Sr

We determine the frequency of the ultranarrow ⁸⁷Sr ¹S₀ - ³P₂ transition by spectroscopy of an ultracold gas. This transition is referenced to four molecular iodine lines that are observed by Doppler-free saturation spectroscopy of hot iodine vapor. The frequency differences between the Sr and the I₂ transitions are measured with an uncertainty of 0.5MHz. The absolute frequency of the ⁸⁷Sr ¹S₀ - ³P₂ (F′=7/2) transition is 446648775(30) MHz and limited in accuracy by the iodine reference. This work prepares the use of the Sr ¹S₀-³P₂ transition for quantum simulation and computation.