On the Theory of Low‐Temperature Exciton Absorption Spectra

The absorption spectrum of Wannier‐Mott excitons at low temperature is studied in the case of weak exciton–phonon coulping. The one‐phonon approximation is used. Only the interaction of excitons with acoustic phonons is taken into account. It is shown that for low temperatures ( k 0 T ≪ 2 m c 2 ) the exciton spectrum consists of a resonant line with its halfwidth tending to zero if T → 0, and of a phonon wing of finite width with the maximum being shifted from the resonant line. In the case T = 0 the resonant line appears to be a zero‐phonon line and the wing represents the vibrational recurrences of the first.