María Florencia Pascual-Winter, Robert-Christopher Tongning, Romain Lauro, Anne Louchet-Chauvet, Thierry Chanelière, Jean-Louis Le Gouët
In low concentration Tm:YAG, we observe efficient adiabatic rapid passage (ARP) of thulium nuclear spin on very long time scales, with flipping time much longer than . Even with an optical oscillator strength as small as a few , optical preparation and detection enable us to work on a sample of about 10 ions. The impurity-doped crystal strongly differs from monoatomic solids where efficient ARP at slow rate was observed in NMR early days. Explanation in terms of isoentropic reversible thermodynamic transformation does not apply in the present experiment. Instead, this feature can be understood as a spin locking effect.