Calculating absorption cross sections

[ctydtgat]

How can I calculate the absorption cross section of a harmonic oscillator in an EM field?

 

[DrDu]

Usually, one would use the golden rule for this:

https://www.google.de/url?sa=t&rct=...rro5AD&usg=AFQjCNEJ67qCpdxJ9NqrVmq3IT4uujQrJwAs a further remark, I want to point out that the coupling of a harmonic oscillator to an EM field may be considerably more complex than via it's dipole moment (just because you didn't say anything about it).