Tham khảo tài liệu 'dictionary of material science and high energy physics part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | relative distances of less than approximately fm 1 fm 10 15 m . hardness Property of a solid determined by its ability to abrade or indent another solid. hard sphere interaction The interaction of particles of finite size modeled with an interparticle interaction that is infinitely repulsive if the separation between the centers of the two particles becomes less than the diameter of the particle . the spheres representing the particles are completely impenetrable. This is also known as the excluded volume interaction. hard superconductor A superconductor that requires a strong magnetic field to destroy superconductivity. harmonic generation A monochromatic light of frequency passing through a nonlinear crystal generates non-linear polarization which is proportional to higher powers of the electric field. This effectively can generate higher order harmonics such as 2 3 etc. Second harmonic generation is most commonly used in nonlinear optics. Harmonic generation requires phase matching and energy conservation within uncertainty limits. harmonic oscillator A particle acted on by a linear restoring force that is a force proportional to the distance of the particle from its equilibrium position and opposite the direction of the displacement. In the presence of such a force a particle performs harmonic oscillations around its equilibrium position. A particle attached to a spring is one example. harmonic oscillator linear A prototype for systems exhibiting small vibrations about an equilibrium point. The Hamiltonian operator H for such a system is h2 d2 2m dx2 1 2 kx2 2 H where k is a force constant. The eigenvalues of the Hamiltonian En consist of an infinite sequence of non-degenerate discrete levels as n 0 h En n 0 1 2 . where h 2n and h is Planck s constant and is the angular frequency. harmonic oscillator potential The potential energy function associated with a linear restoring force see also harmonic oscillator. For a simple harmonic oscillator the .
