HIGH-RESOLUTION NUCLEAR-MAGNETIC-RESONANCE OF SUPERFLUID HE-3-B

High-resolution nuclear magnetic resonance measurements of bulk superf luid He-3-B have been performed at temperatures above 0.5 mK and at pr essures from 0.3 to 21.7 bars. We have found that the resonance freque ncy is shifted from the Larmor frequency of the normal fluid. Accordin g to the theory of Greaves the shift at the superfluid transition dete rmines a specific combination, beta345, of the 5 fourth-order coeffici ents of the order parameter invariants used in the Ginzburg-Landau des cription of superfluid He-3. We found that beta345 approaches the weak coupling limit at low pressure, and decreases at higher pressures qua litatively consistent with the theory of Sauls and Serene but in disag reement with the results of Tang et al.