Electron Spin Resonance of an Irradiated Single Crystal of Ammonium Trifluoroacetate

Abstract

The electron spin resonance of γ‐irradiated single crystals of ammonium trifluoroacetate (CF₃COONH₄) has been investigated at 300° and at 77°K. Free radicals of two types were detected at 300°K. One of these is proved to be CF₂COONH₄ and the other tentatively identified as CF₃CO₂. The nuclear couplings of the two F's of the former are equivalent and axially symmetric with A_∥=188 G and A_⊥=14 G. These couplings indicate spin densities of 0.12 in a 2p orbital of each F. No hyperfine structure is observed for the CF₃CO₂. This is interpreted to mean that the spin density is concentrated on the oxygens. At 77°K the negatively charged radical (CF₃COONH₄)⁻ was found. Its spectrum was observed to change into that for CF₂COONH₄ as the temperature was raised. Different coupling tensors are observed for each of its three F's. The principal elements of the couplings indicate 2p spin densities of 0.11, 0.13, and 0.13 on the three F's.