Magnetometry Using Ramsey Interferometry in a Yb Atomic Beam

We use the Ramsey separated oscillatory fields technique in a 400°C thermal beam of ytterbium (Yb) atoms to measure the Larmor precession frequency (and hence the magnetic field) with high precision. For the experiment, we use the strongly allowed ¹S₀→¹P₁ transition at 399 nm, and choose the odd isotope ¹⁷¹Yb with nuclear spin I = 1/2, so that the ground state has only two magnetic sublevels m_F=±1/2. With a magnetic field of 22.2 G and a separation of about 400 mm between the oscillatory fields, the central Ramsey fringe is at 16.64 kHz and has a width of 350 Hz. The technique can be readily adapted to a cold atomic beam, which is expected to give more than an orderof- magnitude improvement in precision. The signal-to- noise ratio is comparable to other techniques of magnetometry; therefore it should be useful for all kinds of precision measurements such as searching for a permanent electric dipole moment in atoms.