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单词 spin
释义
spin

Physics
  • Symbol ms or s. The part of the total angular momentum of a particle, atom, nucleus, etc., that is distinct from its orbital angular momentum. A molecule, atom, or nucleus in a specified energy level, or a particular elementary particle, has a particular spin, just as it has a particular charge or mass. According to quantum theory, this is quantized and is restricted to multiples of h/2π‎, where h is the Planck constant. Spin is characterized by a quantum number ms. For example, for an electron ms=±½, implying a spin of +h/4π‎ when it is spinning in one direction and −h/4π‎ when it is spinning in the other. Because of their spin, particles also have their own intrinsic magnetic moments and in a magnetic field the spin of the particles lines up at an angle to the direction of the field, precessing around this direction. See nuclear magnetic resonance.


Astronomy
  • A property of many subatomic particles, which behave as though they are spinning, as they have angular momentum that is additional to any orbital angular momentum. However, since there is no way of marking a particle to observe its rotation, this property should not be taken too literally. The units of spin are h/2π‎, where h is the Planck constant.


Chemistry
  • The part of the total angular momentum of a particle, atom, nucleus, etc., that can continue to exist even when the particle is apparently at rest, i.e. when its translational motion is zero and therefore its orbital angular momentum is zero. A molecule, atom, or nucleus in a specified energy level, or a particular elementary particle, has a particular spin, just as it has a particular charge or mass. According to quantum theory, this is quantized and is restricted to multiples of h/2π‎, where h is the Planck constant. Spin is characterized by a quantum number s. For example, for an electron s = ±½‎, implying a spin of +h/4π‎ when it is spinning in one direction and –h/4π‎ when it is spinning in the other. Because of their spin, particles also have their own intrinsic magnetic moments and in a magnetic field the spin of the particles lines up at an angle to the direction of the field, precessing around this direction. See also nuclear magnetic resonance.


Electronics and Electrical Engineering
  • The intrinsic angular momentum possessed by all elementary particles, including the electron and proton. An atomic electron also possesses angular momentum as a result of its orbital motion. Spin is a quantized quantity, the spin quantum number (or spin), s, of particles having either a half integral or integral value. Both electron and proton have spin.

    The magnetic fields produced by an atomic electron’s spin and orbital motion interact in such a way that the electron can exist in either of two closely spaced energy levels. The spin in one level is + and in the other it is −. Because of its spin an electron has an intrinsic magnetic moment.


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