Exciton transitions in quasi-one-dimensional crystals. 9,10-dichloroanthracene

✍ Scribed by K. Syassen; M.R. Philpott

• Publisher: Elsevier Science
• Year: 1977
• Tongue: English
• Weight: 418 KB
• Volume: 50
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(77)80670-2

✦ Synopsis

potsrizeci rcllcctron rpcctra of the first singlet tr,mGtion of tfnr o-crystaIhnc form of 9,l0-circl~IoroantRr3ccr;e arc reported. Crystal faces (OOl), ( 011) and ( 010) were examined in the spcctd range 450 to 350 nm at two tenlpcraturcs, 5 K and 300 K. Two systems of transtricms were observed. The first system is assigned to neutr.ri eucitons. Spectra1 similarittcs with un~l~bst~tuted rtnthrecone and ~r&urncnt5 based on the one~imensrooal stacking of molecules se used to construct e model of the excitcn band structure. Tfic ~-polarized x--c* moIccular transition gives rise to a four branch band with two allowed transitions. The O-0, (As +A,) transition ircs SO-100 cm-r above the bottom of the c_xciton band and the O-Oc, (Ag -, B,) tran\rtion hcs at tflc top ot the band. In the retlcctron spectrum the Davydov sphttmg c'-b for transverse cxcitons IS 210 cm-'. The cxciton band of the O--O molecular transition is not isolated but overlap\ the two-pdrticlc tnanifold of the O-l vrbronic transition. As :I result the O-1,. transitron is unexpcctcdly strong m the spectra off the (010) face. The recond systcrn is polarircd along the st,rck axt~ n and starts 2500 cm-t above the first system. It is tentatively assigned JS a Ilu(Ag + Uu) ch,~rgc transfer excitor1 iransition in agreement with carher observations.