Electron Spin Resonance of γ‐Irradiated Sodium Citrate Pentahydrate and Pentadeuterate

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Abstract
An analysis of the electron spin resonance spectra of γ‐irradiated single crystals of sodium citrate pentahydrate and sodium citrate pentadeuterate, deuterated by exchange with deuterium oxide, indicates that two long‐lived radicals are present in both the protonated and deuterated citrates. One radical is of the form {      ĊH–COONa       –HO–C–COONa       –      CH2–COONa}·5H2O, with principal values of the proton hyperfine tensor of −91.1, −54.2, and −36.7 Mc/sec. The second radical gives a triplet with relative intensities 1:2:1 and splittings of 16 and 15 Mc/sec along the [100] and [001] axes of the crystal, respectively, and a quartet of lines of equal intensity with splitting of 21.5 and 28.0 Mc/sec along the [010] axis of the crystal, due to the interaction of two protons with the unpaired electron. The radical is possibly of the form {      CH2–COONa       –·O–C–COONa       –      CH2–COONa}·5H2O, with the unpaired electron coupling with one proton of each methylene group.