13 17 has to contain at least 10 spins at a temperature of 1 oK to
obtain useful results 10 11 as compared with claims of 10 to 10 spins
for the modern resonance saturation techniques under equivalent
circumstances. This enormous difference can be traced back to two
causes: the ratio of the quality factors of the resonant cavity 4 ('" 1
0 ) and the coils used at audio and sub-audio frequencies (;S 1) and the
ratio of the resonance and relaxation absorption coefficients (oc X")
that are actually measured. Comparing (4. 25) with (5. 5 . . . 8) one
finds that this last factor is of the orderofHIL1 H, the quotient of the
external field and the linewidth of the resonance 2 3 line. This ratio
is of the order 10 for concentrated samples, to 10 for diluted samples.
Literature. Steady state saturation techniques. ESCHEN FELDER, A. H.,
and R. T. WEIDNER: Phys. Rev. 92, 869 (1953). BOLGER, B.: Proc. Koninkl.
Ned. Akad. Wetenschap B 62,348 (1959); - Thesis Leiden 1959. Pulse
saturation techniques. GIORDMAINE, J. A., L. E. ALSOP, F. R. NASH, and
C. H. TOWNES: Phys. Rev. 109, 302 (1958). DAVIS jr., F. C., M. W. P.
STRANDBERG, and R. L. KVHL: Phys. Rev. 111, 1268 (1958). BOWERS, K. D.,
and W. B. MIMS: Phys. Rev. 115, 285 (1959). DREWES, G. W. J.: Thesis
Leiden 1967. Other resonance techniques.