Absolute frequency measurement of the 7s$^2$ $^1$S$_0$ $-$ 7s7p $^{1}$P$_1$ transition in $^{225}$Ra

Understand

Transition frequencies were determined for transitions in Ra in an atomic beam and for reference lines in Te$_2$ molecules in a vapor cell.

• The absolute frequencies were calibrated against a GPS stabilized Rb-clock by means of an optical frequency comb.
• The 7s$^2\,^1$S$_0$(F = 1/2)-7s7p$\,^1$P$_1$(F = 3/2) transition in $^{225}$Ra was determined to be $621\,042\,124(2)\,$MHz.
• The measurements provide input for designing efficient and robust laser cooling of Ra atoms in preparation of a search for a permanent electric dipole moment in Ra isotopes.