JILA, University of Colorado and National Institute of Standards and Technology, Boulder, Colorado 80309-0440, USA.
Phys Rev Lett. 2012 May 11;108(19):193201. doi: 10.1103/PhysRevLett.108.193201. Epub 2012 May 7.
We report the observation of double-quantum coherence signals in a gas of potassium atoms at twice the frequency of the one-quantum coherences. Since a single atom does not have a state at the corresponding energy, this observation must be attributed to a collective resonance involving multiple atoms. These resonances are induced by weak interatomic dipole-dipole interactions, which means that the atoms cannot be treated in isolation, even at a low density of 10(12) cm(-3).
我们观察到了钾原子气体中两倍于单量子相干频率的双量子相干信号。由于单个原子在相应的能量下没有状态,因此这种观察必须归因于涉及多个原子的集体共振。这些共振是由弱原子间偶极-偶极相互作用引起的,这意味着即使在低密度(10(12) ⁇ cm ⁇ ( ⁇ 3))下,原子也不能被孤立处理。