Single crystals of l-ascorbic acid and partially deuterated l-ascorbic acid were irradiated in the temperature range of 77K to 300K by either x-rays from a 3 Mev Van de Graaff electron accelerator or UV radiation (337.1 nm) from a pulsed nitrogen gas laser having a peak power of 240 KW. Several types of free radicals were produced by the radiation and were studied by X-band and Q-band ESR from 4.2K to 300K. The kinds of radicals produced by the UV and x-irradiation were the same. The relative intensities of the spectral lines of the different types of radicals depend upon both the temperature and the type of radiation. Four radicals were identified: two oxidation products (radicals I and IV), one neutralized anion (radical III), and one adduct (radical II). Radicals I, III, and IV are present at 77K after irradiation at 77K. Upon annealing to 140K, radical I changes to dehydroascorbic acid and proton adduction creates radical II. Upon annealing to 300K, radicals II, III, and IV remain and are stable at 300K for at least several months. All four radicals are carbon based radicals and are located on the furan ring. All hyperfine couplings are to (beta)-protons. No carbon-13 hyperfine couplings were observed. ENDOR was tried at 4.2K, 77K, and 300K after x-irradiation at 77K or 300K. In all cases a matrix ENDOR line was observed, but no hyperfine ENDOR lines were observed. UV bleaching was attempted at 300K on a deuterated crystal which had been x-irradiated previously. The UV laser radiation had no observable effect on the ESR spectra in which radicals II, III, and IV were already present. / Source: Dissertation Abstracts International, Volume: 41-10, Section: B, page: 3822. / Thesis (Ph.D.)--The Florida State University, 1980.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_74330 |
| Contributors | MCDEARMON, GRAHAM FISCHER., Florida State University |
| Source Sets | Florida State University |
| Detected Language | English |
| Type | Text |
| Format | 161 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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