tailieunhanh - Dictionary of Material Science and High Energy Physics Part 2

Tham khảo tài liệu 'dictionary of material science and high energy physics part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | leading role in the development of modern nuclear physics. See Copenhagen interpretation. Bohr quantization Rule that determines the allowed electron orbits in Bohr s theory of the hydrogen atom. In an early atomic theory Bohr suggested that electrons orbit parent nuclei much like planets orbit the sun. Because electrons are electrically charged classical physics predicts that such a system is unstable due to radiative energy loss. Bohr postulated that electrons radiate only if they jump between allowed prescribed orbits. These orbits are called Bohr orbits. The conditions required for the allowed angular momenta hence orbits is called Bohr quantization and is given by the formula L nh where L is the allowed value of the angular momentum of a circular orbit n is called the principal quantum number and h is the Planck constant divided by 2n. Bohr radius o 1 The radius of the electron in the hydrogen atom in its ground state as described by the Bohr theory. In Bohr s early atomic theory electrons orbit the nucleus on well defined radii the smallest of which is called the first Bohr radius. Its value is nm. 2 According to the Bohr theory of the atom see Bohr atom the radius of the circle in which the electron moves in the ground state of the hydrogen atom a0 h2 m2 Â. A full quantum mechanical treatment of hydrogen gives a0 as the most probable distance between electrons and the nucleus. Boltzmann constant kB A fundamental constant which relates the energy scale to the Kelvin scale of temperature kB X 10 23 joules kelvin. Boltzmann distribution A law of statistical mechanics that states that the probability of finding a system at temperature T with an energy E is proportional to e E KT where K is Boltzmann s constant. When applied to photons in a cavity with walls at a constant temperature T the Boltzmann distribution gives Planck s distribution law of Ek h ck eh ck KT 1 . Boltzmann factor The term exp e kBT that is proportional to the probability