Quantum Transitional Linewidth of frequency absorption by electron of photon is actually noncommutative nonlocal Dirac Line element

 It's written everywhere that the D2 line has a linewidth of around 6 MHz. But the D2 "line", a transition between fine structure levels, is basically just a composition of the underlying hyperfine lines, which are shifted in frequency by tens of MHz relative to the D2 line.

 All hyperfine sub-levels from a certain fine structure level share the same lifetime / linewidth to a certain accuracy. They are not identical, but the differences are neglectable for most applications. Therefore, people say the D2 line has a linewidth of 6 MHz.

The rate of a certain dipole transitions is, to first order, determined by the dipole matrix element between the corresponding electronic total angular momentums J

.

ΓJ→J′∝⟨J|r|J′⟩2J′+1

The D2 line's hyperfine transitions share the same change in J, namely 3/2→1/2. The only difference between the hyperfine sub-levels with different F from a certain fine structure level is the orientation of the electron spin (up or down), but nevertheless, they share the same J and therefore the same rate / lifetime / linewidth.

https://physics.stackexchange.com/questions/324173/natural-linewidth-of-hyperfine-transitions 

 Photon absorption by an atomic electron occurs in the photoelectric effect process, ... This process requires the incident photon to have an energy greater than the binding energy of an orbital electron.

 For X- and γ-ray photons of sufficient energy, photoelectric absorption is most likely to be caused by the most tightly bound electrons, i.e. those of the K shell, because the concentration of electrons is highest in this shell.... The reaction is also favored at low photon energy and for atoms with a large atomic number, where there are many electron shells for the incoming photon to interact with, and to match in energy. The incident photon is completely absorbed in this process and the electron is released carrying a kinetic energy equal to that of the incident photon minus its binding energy.

 https://www.sciencedirect.com/topics/physics-and-astronomy/photon-absorption

Electronic transitions are not infinitesimally thin, and they all have a certain linewidth Δf, i.e. a span of frequencies below and above the central frequency f0 at which the photon can be absorbed.

  an intrinsic linewidth Δf=1/τ produced by the lifetime τ of the excited state, which is basically an instance of the Heisenberg uncertainty principle: you can't specify the frequency of a wave to something sharper than Δf if its substrate is changing on timescales of order τ.

  if you consider two waves at frequencies f0 and f0±1/2τ, where 1τ≪f0, then they will be pretty much identical, and they will only slip out of phase with each other after a time ∼τ. (cont.)

https://physics.stackexchange.com/questions/434662/can-an-electron-absorb-a-photon-even-if-it-exceeds-the-energy-required-for-the-e

What happens to the wavelength of a photon...A photon transfers a part of in energy to the colloiding electron, so its energy decreases and consequently wavelength increases https://www.doubtnut.com/qna/647812782 

https://www.nature.com/articles/s42005-022-01024-9

 The main phenomena observed include a discontinuous forward transition and a rhythmic phase where a complex order parameter oscillates at constant frequency also in the frame in which the intrinsic frequencies are zero in average.

 new mechanisms for the generation of brain rhythms