Exciton transitions in quasi-one-dimensional crystals. 9,10-dichloroanthracene |
| |
Authors: | K Syassen MR Philpott |
| |
Institution: | IBM Research Laboratory, San Jose, California 95193, USA |
| |
Abstract: | Polarized reflection spectra of the first singlet transition of the α-crystalline form of 9,10-dichloroanthracene are reported. Crystal faces (001), (011) and (010) were examined in spectral range 450 to 350 nm at two temperatures, 5 K and 300 K. Two systems of transitions were observed. The first system is assigned to neutral excitons. Spectral similarities with unsubstituted anthracene and arguments based on the one-dimensional stacking of molecules are used to construct a model of the exciten band structures. The M-polarized ππ* molecular transition gives rise to a four branch band with two allowed transitions. The 0-0b (Ag → Au) transition lies 50–100 cm?1 above the bottom of the exciton band and the 0-0c′ (Ag → Bu) transition lies at the top of the band. In the reflection spectrum the Davydov splitting c′b for transverse excitons is 210 cm?1. The exciton band of the 00 molecular transition is not isolated but overlaps the two-particle manifold of the 0–1 vibronic transition. As a result of the 0–1c′ transition is unexpectedly strong in the spectra of the (010) face. The second system is polarized along the stack-axis a and starts 2500 cm?1 above the first system. It is tentatively assigned as |a(Ag → Bu) charge transfer exciton transition in agreement with earlier observations. |
| |
Keywords: | |
本文献已被 ScienceDirect 等数据库收录! |
|