Cavitation density of superfluid helium-4 around 1 K

Using an optical interferometric method, the cavitation density of bulk superfluid helium at T=0.96K is measured and found to be ρcav=0.1338±0.0002gcm-3. A well-established equation of state for liquid helium at negative pressures converts this to the cavitation pressure Pcav=-5.1±0.1bars. This cavitation pressure is consistent with a model taking into account the presence of quantized vortices, but disagrees with previously published experimental values of Pcav.