Four Q-band EPR spectra (in black) recorded for crystal 3 at 4 K after X-irradiation at 4 K. The first two dose points of 10 and 20 kGy have been scaled by ×5 for clarity. The scan width is 40 mT. The orientation of the crystal was not determined. The simulated spectrum of is shown in blue with the high-g peak explicitly labeled for 20 and 200 kGy dose points. The sharp peak at g ≃ 2.002 becomes apparent at doses above 100 kGy; this is well characterized and is owing to paramagnetic centers trapped in the quartz sample holder. At high field a weak signal is observed in the 10 and 20 kGy spectra (marked by an arrow). This signal is owing to trace amounts of Mn+.