Time-Dependent Statistical Mechanics 11. Absorption spectroscopy
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چکیده
Many absorption spectroscopy experiments can be regarded as situations Lecture 10 10/22/09 continued from N10 in which a system is subject to an additional term in its Hamiltonian that represents interaction of an external field with the system. For example, one of the main ways in which electromagnetic radiation interacts with matter is through a term in the Hamiltonian that is of the form −E(t) · μ, where μ is the electric dipole moment of the system. Another electromagnetic interactions is −H(t) · μm, where μm is the magnetic dipole moment.
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Time-Dependent Statistical Mechanics 14. Electromagnetic absorption by dilute gases
When the electromagnetic field couples to the electric dipole moment of the Continuation of lecture 13 11/5/09 region under consideration, we see that the absorption spectrum, except for simple frequency-dependent factors, is proportional to the Fourier transform of the correlation function of the dipole moment. Using the methods we have been discussing, that correlation function can be written as
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