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

TL;DR

This paper reports precise measurement of the 7s$^2$ $^1$S$_0$ - 7s7p $^{1}$P$_1$ transition frequency in $^{225}$Ra using an atomic beam and optical frequency comb calibration, aiding laser cooling for EDM searches.

Contribution

First absolute frequency measurement of the $^{225}$Ra 7s$^2$ $^1$S$_0$ - 7s7p $^{1}$P$_1$ transition with high precision, supporting laser cooling and fundamental symmetry experiments.

Findings

Transition frequency determined as 621,042,124(2) MHz.

Calibration achieved using GPS-stabilized Rb-clock and optical frequency comb.

Results facilitate development of laser cooling techniques for Ra atoms.

Abstract

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.