pulsed electron spin resonance spectroscopy saturation-transfer electron spin resonance spectroscopy ST-EPR ST-ESR saturation-transfer ESR saturation-transfer EPR saturation transfer spectroscopy CHMO:0000881 Spectroscopy used to measure very slow rotational motions where the response of an atom with an unpaired electron to short (ns) pulses of microwave radiation in a magnetic field is measured. The microwave energy absorbed by the spins is such that there is an equal population of upper and lower spin states (described as 'saturated'). saturation-transfer spectroscopy saturation transfer electron spin resonance spectroscopy