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I want to know whether or not we can detect the absorption due to a single atom. You will need to derive the cross section for an atom to scatter light. we will assume a classical model with a single electron bound in a 1D harmonic potential to a nucleus and driven by a classicial field. (a), write down the equation of motion for the electron .At the moment, leave the damping in terms of an unknown constant r, (b)Determine r by calculating the power delivered to the electron in steady state and equating this to the power radiated by the dipole. (c)Use the Poynting vector to calculate the incident intensity of the laser beam in terms of the electric field. Combine (a),(b) and (c) to obtain the scattering cross section. Finally to determine whether we can observe the absorption use the act that the noise on a laser beam is given by dNp=Np^(1/2), Np is the number of photons/second in the beam. Np=laser power/hw. |
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2楼2009-09-14 05:31:46