Spontaneous emission from a Wigner crystal

Spontaneous emission from a quasi-two-dimensional Wigner crystal is discussed from the quantum-mechanical point of view. We go beyond the dipole approximation and take into account the change in electron position during the de-excitation process. This effect becomes important for the perpendicular electron transition. The results derived for the excitation decay rate indicate (i) a very long electromagnetic lifetime of the first perpendicular excited state and (ii) a significant correction in comparison with the result obtained in the standard dipole theory.