The problem of the viscosity of liquid He ll has been the subject of several recent investigations. In their experiments, Misener, Burton and others at Toronto (1935
a, b
) and later MacWood (1938) at Leiden used the methods of oscillating cylinder and disk respectively. Kapitza (1938) employed radial flow between parallel plates, and Giauque, Stout and Barieau (1938), Burton (1938), and the present authors (1938
a, b
) have used the method of flow through capillaries. There has been wide disagreement among the investigators with regard to the magnitude of the viscosity, and the determination of the value by the different investigators varies from an upper limit of 5 × 10
-9
c.g.s. units, as found by Kapitza (1938), to a value of 10
-5
c.g.s. units, as observed by Burton (1938). In addition to this the present authors reported (1938
a
) that, at least for long, narrow capillaries, the flow of liquid He ll appeared to be non-classical in that the velocity of flow bore a relation to the pressure, which corresponded neither to laminar nor turbulent conditions. Flow is classically defined as laminar when the average velocity over the cross-section of the tube is directly proportional to the hydrostatic pressure which produces the flow. At sufficiently high velocity, the flow ceases to be laminar; it becomes turbulent and the velocity is then proportional to the square root of the pressure. It was observed that for He ll in long, narrow capillaries the velocity became almost independent of pressure and the suggestion was advanced that this might be attributed to slip on the walls of the capillary.
Upper-limit determination of resonant trielectronic recombination cross-section for krypton using crystal channeling
