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Elastic Collisions

This kind of collision affects only the off--diagonal elements of the density matrix and principally dephases the dipole moment of the atoms, i.e., it throws atoms out of alignment with the electromagnetic field. This alignment could be different for all of our Avogadro's number of atoms. Therefore, these collisions will ultimately send the dipole moment of the system to zero.

u and v have been identified as being the dispersive and absorptive portions of the system's dipole moment. The magnitude of the dipole moment can be found by: . The Bloch window allows the user to plot this value as a function of time.

Let all the atoms initially be in the lower state. Set Amp=0.10 and Freq=1.00 and turn the elastic collisions on with . Plot and uvw versus time. In Figure gif, what is the steady state of this system?

  
Figure: Rabi oscillations including elastic collisions Amp=0.10, Freq=1.00, and

Compare the uvw plot found for this experiment and the one for inelastic collisions. What do you notice about both of these experiments? How are they different? the same? (Hint: Compare the plots)

Plot the dipole moment for elastic collisions and then plot it for inelastic collisions. Notice that in both cases the dipole moment decreases to zero.



Andy Antonelli
Wed May 17 14:34:24 EDT 1995