 Rydberg exciton

A Rydberg exciton is an excited bound electron-hole state with a large principal quantum number. Like a Rydberg atom, it can have a large spatial extent and strong sensitivity to external fields, but its energies and size are modified by the semiconductor's effective masses and dielectric response.

Experiments on cuprous oxide resolved high-lying excitonic states, allowing hydrogen-like series behavior to be studied in a solid. Deviations from a simple Coulomb model reveal crystal and band-structure effects.^[ref]