Laser-cooling and trapping of Ytterbium atoms
Dr. Umakant Rapol (Laboratoire Kastler Brossel, ENS Paris)

Laser-cooled Ytterbium (Yb) offers varied possibilities for precision measurements involving fundamental symmetries and atomic frequency standards. It has seven stable isotopes both Fermions and Bosons. The low lying electronic transitions in Yb are easily accessible using readily available lasers. Due to the ease of laser cooling of Yb and possibility of increased number density, it can became an important candidate for the proposed experiments in the measurement of atomic parity non-conservation¹ and for measurement of permanent Electric Dipole Moment² of atoms to test theories beyond the standard model.

For Yb, there exists a highly forbidden transition which acquires a finite transition probability in odd isotopes due to hyperfine coupling. This transition has been recently shown to have a natural linewidth of < 10 mHz³.
This attracts the use of laser cooled Yb in zero light shift optical lattice for precise frequency reference, complimentary to the ongoing efforts for a Strontium (Sr) clock⁴.

In this talk, I will first briefly give the motivation for our interest in laser cooling Yb atoms. And then I will present the results of the Yb Magneto-optic trap (MOT) loaded directly from a thermal source⁵.
We load all the seven stable isotopes including the rarest of all the isotopes, inspite of using a thermal source. We study the primary loss mechanisms in the MOT and show that the life time of the MOT is mainly limited by the branching of the excited state into the metastable levels which do not decay back to the ground state.

References:

1. David DeMille, Phys. Rev. Lett. 74, 4165 (1995)

2. Angom Dilip Singh, PhD thesis, Indian Insitute of astrophysics, Bangalore

(INDIA)

3. Porsev et al., Phys. Rev A, 69, 021403 (2004)

4. M. Takamoto and H. Katori, Phys. Rev. Lett. 91, 223001 (2003)

5. U. D. Rapol et al., Euro. Phys. J. D, DOI: 10.1140/epjd/e2004-00041-3