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Imagine an electron around an atom absorbs a photon and becomes excited, it has now jumped to a higher orbital. At this point in time, where does the momentum of the photon goes?

Qmechanic
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user6760
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1 Answers1

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Emilio's answer (How does one account for the momentum of an absorbed photon?) is great but quite technical. The simplified version is some of the momentum is accounted for by the different linear momentum associated with different orbitals. From the Bohr model we have $$p_n=\dfrac{\hbar}{a_0 n}$$ where $n$ is the principal quantum number which changes when an atom is excited. The rest of the momentum causes the atom itself to recoil. This is the mechanism whereby a photon absorption can excite a phonon (it kicks the atom which sets the lattice vibrating).

bRost03
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