Solid-state sucrose is a well-known
dosimetric system, which is
capable of reliable dose estimates only at a considerable time after
exposure. Immediately after irradiation at room temperature, its electron
paramagnetic resonance (EPR) spectrum is dominated by contributions
from unstable radicals, which are studied here using continuous-wave
EPR and electron–nuclear double resonance (ENDOR) spectroscopy.
Four hyperfine tensors of proton couplings were determined, associated
with two radical species, and subsequently compared to density functional
theory calculation results, which led to the identification of the
species with lower abundance (U2) as a radical formed by a H abstraction
from C4. The more abundant center (U1) has not been definitively identified
yet, but we present compelling evidence that it should be a C6 centered
radical. Comparison of the simulated EPR spectra with all available
data to the experimental ones suggests that the EPR spectrum of X-irradiated
sucrose immediately after irradiation can now be almost entirely understood.