ESR of triplet excitons in 1.4 dibromo-naphthalene. Linear excitons

✍ Scribed by R. Schmidberger; H.C. Wolf

• Publisher: Elsevier Science
• Year: 1972
• Tongue: English
• Weight: 527 KB
• Volume: 16
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(72)80303-8

✦ Synopsis

The ESR spectrum of metzstable triplet escitons in sinple cryst:k of 1.4 dibromrrnaphthalene (1.4 DRN) nt 1.4"K and 35 GHz W;IS investigated. Optical measurements have established previously :hnt in this system escitons are free even at 1.1' IL Esciton motion in these crystals takes place main!y by hoppin: between translationally equivalent molecules along rhe crystal c asis (AA jumps). This fact is due to the crysti I structure of 1.1 DBN and the escitons are therefore called linear cscitons. The ESR spectra were obsewed both directly (standard microwave dexction) 2nd optically, usin, ~7 the phosphorescence intensity of individual Zeeman components of pl~ospI~orcs~enc~ lines as indicator. Using optical detection one can easily distin_cuish beiwecn the free esciton ESR nnd ESR lines which xc due to isolated trap molecuI~'s in the crystal.

The ESR spectra show clearly the one-dimensional character of escitons in these crystals. In addition one can measure the inter-cllain jump rates between translationally inequivalent chains (AB jumps), by studying the line shape and line width of the ESR lines 'These rates are three orders of magnitude smaller than those of in-chain jumps. The inter-chain jumps are also responsible for the spin-lattice rclas:ation time T 1. T1 WIS measured and calculated using the mathods which wcrc devclopcd earlier for cscitons in naphthalone and anthracene.