Summary form only given, as follows. Spontaneous emission from nuclear spins has been measured for the first time. This is possible because of the use of a low-noise SQUID amplifier with noise temperature (0. 2 K) less than that of the 1. 5 K helium bath. The spontaneous emission power is 5-10% of the background circuit Nyquist noise, which corresponds to the ratio of the effective spin resistance R//s (proportional to the nuclear susceptibility) and circuit resistance R. Although only one spin flip occurs per 10**8 yr due to spontaneous emission, the effect is magnified, because all 10**2**2 spins in the sample contribute independent of the temperature. This technique implies that spectra of spins can be measured without the requirement of a net polarization and might be useful for samples where spin lattice relaxation times are impractically long. Radiation damping terms which are added to the Bloch equations allow for spin noise analysis of power flow between the spin system and cavity. The equivalence is obtained of predictions of Nyquist's theorem at all spin temperatures T//s and bath temperatures T in conformity with the predictions of the Einstein detailed balance equation for spontaneous emission.
|Original language||English (US)|
|Title of host publication||Unknown Host Publication Title|
|Publisher||Optical Soc of America|
|Number of pages||1|
|State||Published - 1987|
ASJC Scopus subject areas