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Green exciton series in cuprous oxide

We numerically investigate the odd parity states of the green exciton series in cuprous oxide. Taking into account the coupling to the yellow series and especially to the yellow continuum, the green excitons are quasi-bound resonances with a finite lifetime which cannot be described with Hermitian operators. To calculate their positions and linewidths, we use the method of complex-coordinate rotation, leading to a non-Hermitian complex eigenvalue problem. We find that the behavior of the dominant P states is very well approximated by a modified Rydberg formula using a negative quantum defect. The corresponding linewidths induced by the coupling to the yellow continuum decrease with the third power of the principal quantum number.