Characteristics of trapped electrons and electron traps in single crystals

Abstract

Two additional carbohydrates are reported whose crystal structures trap electrons intermolecularly in single crystals x irradiated at low temperature, namely sucrose and rhamnose. Five carbohydrate and polyhydroxy compounds are now known which exhibit this phenomenon. The following characteristics of the phenomenon were investigated: (1) the hyperfine couplings of the electron with protons of the polarized hydroxy groups forming the trap; (2) the distances between these protons and the trapped electron; (3) the spin density of the electron at the protons and (4) the relative stabilities of the electron trapped in various crystal structures.

Radiation Chemistry of Solid-State Carbohydrates Using EMR

“…6.9e). The ENDOR and EIE spectra recorded for the broad-line EPR spectrum correspond to the IMTE as reported by Budzinski et al [108]. In particular, the slightly lower g value of the IMTE triplet contribution is clearly recognizable.…”

“…Box and co-workers have characterized IMTEs in a number of compounds, as nicely summarized in the review by Lund and Schlick [134]. The group of Box has characterized an even larger number of primary alkoxy radicals in carbohydrates [107][108][109]144]. These authors, however, seldom discussed secondary radicals and radical reactions.…”

“…In previous investigations of sucrose irradiated at liquid helium temperature, an inter-molecularly trapped electron (IMTE) center had been detected and found to be stable in the dark up to ~60 K [108,109]. Like in other carbohydrates, this IMTE was characterized by large and anisotropic HF interactions with exchangeable protons and by a nearly isotropic g value, slightly smaller than the freeelectron value.…”

“…Consequently, it has so far not been possible to determine the location of the IMTE by direct comparison of calculated and experimental HF tensors. It may however be anticipated that the electron will be trapped in the dipolar field between at least two OH-dipoles in carbohydrate crystals [108][109][110][111][112]. Plausible sites for inter-molecular electron trapping in carbohydrates have been calculated applying the semi-continuum potential model [110], and considerable rearrangements of OH-dipoles, even at 4 K, have been suggested.…”

“…Plausible sites for inter-molecular electron trapping in carbohydrates have been calculated applying the semi-continuum potential model [110], and considerable rearrangements of OH-dipoles, even at 4 K, have been suggested. In the particular case of sucrose, the most plausible site for the observed IMTE was determined by analysis of the anisotropy of non-exchangeable proton interactions, observed with ENDOR [108]. This site is shown in Fig.…”