CommunicationThe first observation of Carbon-13 spin noise spectra

We demonstrate the first 13C NMR spin noise spectra obtained without any pulse excitation by direct detection of the randomly fluctuating noise from samples in a cryogenically cooled probe. Noise power spectra were obtained from 13C enriched methanol and glycerol samples at 176 MHz without and with 1H decoupling, which increases the sensitivity without introducing radio frequency interference with the weak spin noise. The multiplet amplitude ratios in 1H coupled spectra indicate that, although pure spin noise prevails in these spectra, the influence of absorbed circuit noise is still significant at the high concentrations used. In accordance with the theory heteronuclear Overhauser enhancements are absent from the 1H-decoupled 13C spin noise spectra.

118Highlights► We report the first observation of Carbon-13 spin noise spectra. ► Non-linear amplitude response at high concentration indicates the influence of radiation damping. ► The proton decoupled noise spectra show absence of heteronuclear NOE enhancement.