Mechanism of Absorption of Light by Free Continuum Polarons

The absorption of light by free continuum polarons is treated in the framework of the Landau-Pekar approach which for this problem is not restricted to strong coupling but gives at least the qualitative behavior for intermediate coupling ($\alpha \approx 3 \mathrm{to} 6$). The absorption curve consists of a relatively narrow zero-phonon peak and a broad sideband showing a multiphonon structure. The zero- and one-phonon contributions and the lowenergy part of the two-phonon contribution have been evaluated numerically.