Alloying Effect on the n = 1 and n = 2 Excitons in Mixed K_1-xRb_xI Crystals

Abstract

Alloying effect on the exciton reflection spectra has been studied for mixedK_1-xRb_xI single crystals (0 ≤ x ≤ 1) at 10 K. Theshoulderlike structure of the n = 1 exciton band, which arises from theexciton-phonon interaction, is kept well over the whole concentration range. On the other hand, the multiple LO-phonon sidebands of the n = 2 exciton aresmeared out upon alloying. These results reveal that the alloying effect isvery sensitive to the spatial extension of excitons. Furthermore, free-excitonluminescence is observable even in the intermediate region of x, indicating that the exciton is not localized by the potential fluctuations in K_1-xRb_xI crystals.