Edited:- Does the total dipole moment of an atom and induced dipole moment between two levels interact together for a transition?
Atoms neither in a ground state nor any eigenstates (without interactions) have any dipole moment. Dipole moment of atoms is a result of superposition of different eigen states. See attatched link for illustrative simulations of this fact.
During interaction of a ground state atom with EM field, such superposition between higher level arises. In case of no decoherence it yields Rabi oscillations (also seen in that simulation). This induced will continue to interact with EM field but it is still the same one dipole moment.
Probably it is easier to see it in a classical picture where EM field can simply displace electron cloud from the nucleus, event there was no intial dipole moment, and then this displaced moment will continue to interact with EM field in a sense that e.g. can retard the EM wave (origin of refractive index).
See also attatched book.
http://www.falstad.com/qmatomrad/
Book Quantum Optics
Dear Zwan,
Could you please tell me, how are the induced dipole moment b/w two states and induced dipole moment in an atom correlates? Could you please give me a correct picture regarding the atomic transition(in two level only) and role played by dipole moments (in presence of driving filed).
Thanks
Dear Anil and Colleagues,
Two little things that I'd point out germane to Anil's question. In a strict sense the induced dipole and the incident field can/do interfere, and that interference is directly correlated with absorption in the atom. Think of it this way; in a simple steady state quantum optics model where you are looking at the total electric field downstream from the atom you have the sum of the incident field and the dipole contribution. The phase difference between the two (due to retardation associated with the non-hermitean terms in the response...the decay rates for the excited state and the dipole for example) causes there to be interference leading to less light downstream. That is precisely the light absorbed, as can be shown rigorously.
Final point; if the incident field rolls over multiple resonant atoms the induced dipoles do interact with one another. This is a well studied process, of particular importance for non-linear optical processes and one name it goes under that can be a keyword for searching further about such a process is "cascading". Yours, -Mike Crescimanno, YSU Physics
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