Features of the exciton–phonon interaction in nitrogen cryocrystals

The exciton absorption at the transitions a1Πg←X1Σg+ and w1Δ0←X1Σg+ is studied in α-N2 and N2−Ar in order to determine the features of the exciton-phonon interaction in α-nitrogen. The first spectral moments of the vibronic transition bands are calculated for pure and impure crystals, and evidence is found that both free and self-localized excitons are manifested in the absorption spectrum of α-nitrogen. The parameters of the exciton–phonon interaction are estimated. It is established that in solid nitrogen the a- and w-excitations correspond to excitons with effective masses of opposite sign. Analysis of the temperature dependence of the first moments of the absorption band w(0)←X(0)3 shows that for α-nitrogen there is a linear exciton–phonon interaction in the temperature range 6−30 K.

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