“quantum theory of radiation”的概念、定义、翻译、参考文献-科学参考

quantum theory of radiation

Physics

The study of the emission and absorption of photons of electromagnetic radiation by atomic systems using quantum mechanics. Photons are emitted by atoms when a transition occurs from an excited state to the ground state. If an atom is exposed to external electromagnetic radiation a transition can occur from the ground state to an excited state by absorption of a photon. An excited atom can lose the energy it has gained by stimulated emission (see laser). However, an excited atom can also emit a photon in the absence of external electromagnetic radiation, a process called spontaneous emission. The quantum theory of radiation was initiated by Einstein in 1916–17, as an extension of Planck’s radiation law. The theory is quantified by the Einstein coefficients. The quantum theory of radiation is the basis of the theory behind the operation of lasers and masers.

Chemistry

The theory that describes the emission and absorption of electromagnetic radiation. Since it is a quantum theory the processes of emission and absorption are described in terms of the creation and disappearance of photons, with photons being created in emission processes and disappearing in absorption. Absorption occurs when electromagnetic radiation that impinges on a quantum mechanical system, such as an atom or molecules, induces a transition from the ground state of the system to an excited state by virtue of a photon of the radiation being absorbed. Similarly, emission of a photon occurs when an atom returns to the ground state from an excited state, i.e. spontaneous emission occurs. It is also possible for an atom in an excited state to emit a photon by induced emission, a process that is used in lasers.

单词	quantum theory of radiation
释义	quantum theory of radiation Physics The study of the emission and absorption of photons of electromagnetic radiation by atomic systems using quantum mechanics. Photons are emitted by atoms when a transition occurs from an excited state to the ground state. If an atom is exposed to external electromagnetic radiation a transition can occur from the ground state to an excited state by absorption of a photon. An excited atom can lose the energy it has gained by stimulated emission (see laser). However, an excited atom can also emit a photon in the absence of external electromagnetic radiation, a process called spontaneous emission. The quantum theory of radiation was initiated by Einstein in 1916–17, as an extension of Planck’s radiation law. The theory is quantified by the Einstein coefficients. The quantum theory of radiation is the basis of the theory behind the operation of lasers and masers. Chemistry The theory that describes the emission and absorption of electromagnetic radiation. Since it is a quantum theory the processes of emission and absorption are described in terms of the creation and disappearance of photons, with photons being created in emission processes and disappearing in absorption. Absorption occurs when electromagnetic radiation that impinges on a quantum mechanical system, such as an atom or molecules, induces a transition from the ground state of the system to an excited state by virtue of a photon of the radiation being absorbed. Similarly, emission of a photon occurs when an atom returns to the ground state from an excited state, i.e. spontaneous emission occurs. It is also possible for an atom in an excited state to emit a photon by induced emission, a process that is used in lasers.
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