Jeudi 3 juin 2004
Liquid, solid and cold gaseous helium provide environments to neutral impurity atoms suitable for testing fundamental atomic and molecular physics.
Here, I discuss mainly alkali-metal atoms in cold helium gas, after showing briefly some unique properties of such atoms in superfluid helium. I first present a method to gently produce gaseous alkali atoms in a glass cell cooled to a low temperature. Since the produced atoms have a lifetime and a spin (electron spin) relaxation time as long as 100 s, they allow the precise measurement of the atomic permanent electric dipole moment (EDM).
This measurement offers a direct test of time-reversal symmetry. Then, I turn to alkali-helium molecules (MHen ; n=1,2,...), which are formed only at a low temperature of about 10 K.
I discuss the structure and growth of these molecules, on the basis of their observed spectra in the visible and near infrared.