 Nuclear magnetic resonance fingerprint of superfluid helium-3

Transverse nuclear magnetic resonance measures absorption from a radio-frequency magnetic field perpendicular to the static field. In the A phase, the resonance moved above the Larmor frequency; in the B phase it returned to that frequency despite the changed state. Anthony James Leggett connected the shift to collective spin-orbit structure. A predicted longitudinal resonance, driven parallel to the static field, supplied a further B-phase test.^[ref]

The helium-3 superfluid discovery experiment establishes why a new phase was inferred; comparing response channels then tests its internal structure. An unchanged peak in one geometry cannot, by itself, establish that nothing ordered.