Properties of Liquid Helium

The behavior of a multi-particle system with a symmetric wave function differs markedly from the behavior of a system with an antisymmetric wave function. Particles with integral spin and therefore symmetric wave functions satisfy Bose-Einstein statistics and are called bosons, while particles with antisymmetric wave functions satisfy Fermi-Dirac statistics and are called fermions. Systems of " He atoms (helium-4) and of He atoms (helium-3) provide an excellent illustration. The " He atom is a boson with spin 0 because the spins of the two protons and the two neutrons in the nucleus and of the two electrons are paired. The He atom is a fermion with spin because the single neutron in the nucleus is unpaired. Because these two atoms obey different statistics, the thermodynamic and other macroscopic properties of liquid helium-4 and liquid helium-3 are dramatically different. 

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. 

Properties of Ice and Supercooled Water, 6-8 Properties of Liquid Helium, 6-132 Properties of Magnetic Materials, 12-105... 

The other vital consideration affecting the possibility of solidification and influencing also almost all of the other properties of liquid helium is its very high zero-point energy. In quantum mechanics, the lowest permitted kinetic energy for a particle is not necessarily zero. If a particle of mass m is confined to a volume F, then its minimum kinetic energy, or zero-point energy, is... 

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