Timeline for By what mechanism is a photon emitted or absorbed in atomic electron state transitions?
Current License: CC BY-SA 3.0
8 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Dec 31, 2015 at 22:04 | vote | accept | D. W. | ||
| Dec 31, 2015 at 22:03 | comment | added | D. W. | Thank you so much, it's hard to get over the non-probability picture. Especially when the picture of the photon as a continuous oscillating electromagnetic-field is so commonly touted. Thinking of the photon as an excitation in a field, in which it's incorrect to view it as "traveling" from one point to another, even though you may detect it at that one point, and then detect it at the other, is hard to solidify. | |
| Dec 31, 2015 at 21:52 | comment | added | CuriousOne | @D.W.: The detection probability for the photon "after" the interaction is finite. The excited state has a finite lifetime, which means that there is (except maybe for infinitesimally short moments) always a finite probability to get an outbound photon distribution. Technically all of this also happens at a finite temperature (the third law of thermodynamics still applies!), so one would actually have to consider the density matrix of the system for finite T, rather than just the T=0 field equations. Moreover, the equations describe stimulated emission, as well. | |
| Dec 31, 2015 at 21:48 | comment | added | CuriousOne | @D.W.: For atomic systems you would use the equations of quantum electro dynamics, the (inhomogeneous) Dirac equation is part of them (for the electrons), the other part is for the description of the electromagnetic field. You also have to chose a particular gauge, I believe, but you better ask a theoretical physicist to explain the details, I have never worked with these equations myself. The currents originate from the charge conservation and the entire form of the equation can be derived from symmetry considerations and he necessity to rediscover EM fields in the classical limit. | |
| Dec 31, 2015 at 21:40 | comment | added | D. W. | What is that dynamic equation? The Dirac equation? And how does the coupling of the bound electron to the electromagnetic field allow for the system to go from being in a "non-zero photon detection probability and an electron in one state" to a "infinitesimal photon detection probability and electron in a different state"? Or vice versa? The "current" from the electron changing states produces a change in the electromagnetic field? | |
| Dec 31, 2015 at 21:34 | comment | added | CuriousOne | @D.W.: No, neither forces not accelerations make any sense in quantum mechanics. Those are macroscopic quantities that can be derived as thermodynamic averages over the dynamics of quantum systems, but if you are talking about atoms and their coupling to electromagnetic fields, then these classical descriptions don't make any sense. There is, of course, a dynamic equation that describes the change of these fields as a function of time and it even has a very deep structural connection to the equations of classical physics, but one does not recover forces from it but so called currents. | |
| Dec 31, 2015 at 21:31 | comment | added | D. W. | The non-Newtonian picture still leaves room for forces and interactions, no? By what force or interaction does the photon interact with the electron during emission and absorption? What interaction between the photon and the electron accounts for a non-zero probability of detecting the photon before and an infinitesimal probability of detecting the photon after, along with the change in the electrons energy-state? Or are we complacent with just saying "the probability distribution changed, and we don't know what happened in the interim"? | |
| Dec 31, 2015 at 21:17 | history | answered | CuriousOne | CC BY-SA 3.0 |