Surface tension liquid helium

The eorresponding result for the surface tension [9] provides quite reasonable accuracy for a Leonard Jones fluid or an inert gas fluid, except helium whieh displays large quantum effeets. Thus we ean eonelude that the leading mechanisms of surface tension in a simple fluid is the loss of binding energy of the liquid phase at the gas-liquid interface and the seeond most important meehanism is likely to be the adsorption-depletion at the interface whieh ereates a moleeularly smooth density profile instead of an abrupt step in the density. 

Liquid helium suffers no obvious change in surface tension at the transition (A) point (J. F. Allen and A. D. Misener, Proc. Camb. Phil. Soc., 34, 299 (1938)). 

The Kelvin equation takes into account molecule/solid and intermolecular interactions using contact angle and surface tension, respectively. However, the Kelvin approach is not appropriate for de.scription of adsorption on small mesopores. Saam and Cole developed the thermodynamic theory with the average molecular potential for liquid helium in a cylindrical pore in order to understand unusual properties of liquid helium[19,20]. Findenegg et al have applied the Saam-Cole theory to elucidate fluid phenomena near the critical temperature[21]. The Saam-Cole theory includes the molecule/solid interaction in a form of the sum of the dispersion pair interactions. The Saam-Cole theory is fit for description of adsorption phenomena in regular mesopores[22j. 

Dyugaev, A.M., and Grigoriev, P.D. (2003) Surface tension of pure liquid helium isotopes, JETP Letters 48, 466-470... 

Liquid helium is, next to hydrogen, the lightest liquid known. Its density 2 at4°.33A. is 0.1208 and at 2°.4A. it is 0.1459. The temperature of maximum density is 2°.2 A-, the critical temperature is 5°.25 A., and the critical pressure 2.26 atmospheres. Liquid helium is colorless, very mobile with very small surface tension. When evaporated under diminished pressure a temperature as low as 2°.5 A. was obtained,3 but no solid helium resulted, Onnes failed to obtain solid helium at a temperature of 0.82° A. 

The model was first elaborated to explain the anomalously high lifetime observed in liquid helium, which has a large electron density compared with the gaseous state [Fe 57, Ro 67]. It was later extended to molecular liquids with low surface tensions [Bu 71], and it was subsequently demonstrated [Le 76] that it can also be applied to aqueous solutions of inorganic substances where surface tensions are high. 

L/V surface tension values can be used to estimate solid/liquid (S/L) and solid/vapor (S/V) surface tensions of binary liquids from the classical force balance projected on the helium/ binary liquid mixture/SS304 screen pore interface as follows ... 

The actual interface temperature within the screen pores may be different from the measured liquid screen side temperature due to enhanced heating (vapor case) or cooling (helium case) at cryogenic temperatures. In Equation (3.16), surface tension is evaluated based on the liquid screen side temperature, but the helium data in Figure 5.10 imply that the interfacial temperature is cooler than the liquid screen side. In other words, unlike storable bubble point data, for cryogenic bubble points, it matters which pressurant gas is in contact with the screen. 

At 1.00 K, the surface tension of liquid helium is 0.347erg/cm. What is the pressure difference in a droplet of liquid helium whose radius is 0.0055 mm at this temperature ... 

---