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Need to discuss about quantum concepts

  1. Sep 17, 2013 #1
    Hi all.

    I'll starting a little research for my college assignment. But I need to discuss a few concepts in Quantum Mechanics [sorry for my english].

    1. I want to analyze perturbation effect that suffered by an ion. Is Rayleigh-Schrodinger theory suitable for this problem? if not, which suitable theory for it?

    2. If an electromagnetic wave is passed to a atom, it will be absorbed by an electron and then emitted a photon when back to old level energy. So, where will the photon go (if a chain reaction is not exist)? is will merge with the electromagnetic wave or?

    Thank you.
  2. jcsd
  3. Sep 18, 2013 #2
    That depends on what is causing the perturbation. If the perturbation Hamiltonian is static, then Rayleigh-Schrödinger (more commonly called time-independent perturbation theory these days) is the correct tool. If the perturbation is a function of time—as a passing electromagnetic wave is—then you need time-dependent perturbation theory. If you want to examine the effect of interactions with photons, then you need quantum electrodynamics.

    Absorption is not the only option, you can also have stimulated emission. If you're treating the EM radiation quantum mechanically (i.e. as a photon) then you can also get a variety of scattering interactions like Compton scattering. If stimulated emission occurs, the photon will be of the same phase, wavelength, polarization and direction as the stimulated photon (which obviously puts constraints on the energy required by a photon to induce emission). On the other hand, spontaneous emission (that follows absorption) is much less restricted and can produce photons very different than the one that was absorbed. I'm not really sure what you mean by "merge with the electromagnetic wave". The photon will propagate away from the atom.
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