In one aspect, the present invention provides a method for enhancing the sensitivity of liquid-state NMR or MRI experiments. In general, the method involves providing a frozen sample in a magnetic field, wherein the frozen sample includes a polarizing agent with at least one unpaired electron and an analyte with at least one spin half nucleus; polarizing the at least one spin half nucleus of the analyte by irradiating the frozen sample with radiation having a frequency that excites electron spin transitions in the at least one unpaired electron of the polarizing agent; melting the frozen sample to produce a molten sample; and (d) detecting nuclear spin transitions in the at least one spin half nucleus of the analyte in the molten sample. In certain embodiments, the methods further comprise a step of freezing a sample in a magnetic field to provide the frozen sample in a magnetic field.