Influence of impurity concentration on local exciton spectra in naphthalene crystals

• Published in: Journal of luminescence 1971, Vol.4 (3), p.261-270
• Main Authors: Ostapenko, N.I., Sugakov, V.I., Shpak, M.T.
• Format: Article
• Language: English
• ISSN: 0022-2313; 1872-7883
• DOI: 10.1016/0022-2313(71)90077-9

The influence of an impurity molecule on the properties of local excitons in the naphthalene crystal has been studied in detail theoretically and experimentally. Luminescence and absorption spectra of indole-doped naphthalene single crystals were studied at T = 4.2°K. It is shown that with an increase of the impurity concentration, a new series of bands appears in the luminescence spectrum which is shifted with respect to the luminescence spectrum of single local centres towards long waves and whose O-O band is polarized largely along the a-axis of the crystal. Also, another longer wave-length series is visible in the spectrum whose intensity increases with the impurity concentration. The origin of these series can be explained by the formation in the naphthalene crystal of new states of local excitons due to simultaneous perturbation of two neighbouring translationally nonequivalent molecules of naphthalene (L 2-centres) and to a perturbation of a host molecule by the two guest molecules (2L-centres). The experimental results show good agreement with the theory.