Allowed and forbidden transitions in artificial hydrogen and helium atoms

摘要: The strength of radiative transitions in atoms is governed by selection rules that depend on the occupation atomic orbitals with electrons1. Experiments have shown2,3,4,5 similar electron quantized energy levels semiconductor quantum dots—often described as artificial atoms. But unlike real atoms, confinement potential dots anisotropic, and electrons can easily couple phonons material6. Here we report electrical pump-and-probe experiments probe allowed ‘forbidden’ between under phonon emission one or two (artificial hydrogen helium atoms). forbidden are fact higher-order processes where flip their spin. We find relaxation time about 200?µs for transitions, 4 to 5 orders magnitude longer than transitions. This indicates spin degree freedom well separated from orbital freedom, total an excellent number. encouraging result applications basic entities spin-based information storage.