Structure and selected ESR lineshapes of the spin probe TEMPOL in water.

Left: slowly cooled bulk water (SC protocol). Right: quenched and slowly re-heated bulk water at the indicated temperature (QRW protocol). The QRW sample contains ice with higher polycrystallinity. Note that the SC sample at 210 K exhibits narrower lines than QRW sample at K, i.e. TEMPOL is rotating faster in SC water. The H-bonding of TEMPOL with water is shown in the top of the the right panel. Owing to the very weak ESR signal from TEMPOL in the SC sample at K, a small spurious signal from the quartz capillary used is observed at G.