Quantum momentum distribution and kinetic energy in solid 4He.
We present measurements of neutron scattering from solid 4He at high momentum transfer. The solid is held close to the melting line at molar volume 20.87 cm3/mol and temperature T=1.6 K. From the data, we determine the shape of the momentum distribution, n(k), of atoms in the solid and the leading final state contribution to the scattering. We show that n(k) in this highly anharmonic, quantum solid differs significantly from a Gaussian. The n(k) is more sharply peaked with larger occupation of low momentum states than in a Maxwell-Boltzmann distribution, as found in liquid 4He and predicted qualitatively by path integral Monte Carlo calculations. The atomic kinetic energy is =(24.25+/-0.30) K. If n(k) is assumed to be Gaussian, as is usually the practice, a 10% smaller is obtained.
Quantum Momentum Distributions
The atomic momentum distribution in quantum fluids and solids differs significantly from the classical, Gaussian Maxwell–Boltzmann distribution. There are more low momentum atoms than in a Gaussian. Using simple models, we show that deviation from Gaussian of the observed magnitude and sign can arise from anharmonicity in the potential or from the introduction of Bose statistics.
Body sculpturing.
Significant improvements in body contour can be accomplished by surgical procedures having reliable, predictable results. Similar to the modern sculptor of inanimate art forms, plastic surgeons have utilized new materials and devised new techniques to achieve aesthetic improvement of the face, trunk, and extremities. The goals of the surgical sculptor are perhaps more challenging than those of the pure artistic sculptor, not only because they must result in improved appearance but also because the surgeon is limited at all times by considerations of regional anatomy, the availability of viable tissue materials, and the safety of his patient.