Mutual friction measurements in uniformly rotating liquid helium

The mutual friction parameters B exp and B' exp defined by Hall have been measured under the same experimental conditions over the temperature range from 1.4 degrees K to within a few mdegK of the lambda point, the parameter B' exp to greater precision than previous measurements. In general the data agree with those of previous authors except those of Lipa et al. on B exp near the lambda point. The data have been used to calculate values of the parameters chi and chi ' using Hall's model for the scattering of rotons by vortex lines. In the temperature range where comparison is meaningful the value of chi is an order of magnitude larger than Lifshitz and Pitaevskii's theoretical estimate, but order of magnitude agreement is obtained on the parameter chi .