1. Energy Level diagram for n- 2 level atoms

2. Radiation from an Extended Sample Destroy photon Raise Energy level Interaction with Radiation field

3. Radiation from an Extended Sample By some sort of change in basis:

4. “Spin” operators are the same as before Absorption or emission of a photon with momentum k, Radiation Rate in k direction:

5. Non-linear Rayleigh scattering/superradiance Collective scattering: Dicke superradiance Rayleigh: Inouye et al., Science (1998)

6. Non-linear Rayleigh scattering/superradiance Recoiling atoms interfere with stationary atoms to form a diffraction grating, which then enhances scattering into that mode The Scattered Power

7. Dicke’s Superradiance?

8. Non-linear Rayleigh scattering/superradiance Dipolar emission pattern radiates weakly along polarization axis, collective scattering is stronger along long axis I ~ 1-100mW/cm^2 t ~ 50 ms Superradiant decay of atoms Normal decay of atoms

9. References Coherence in Spontaneous Radiation Processes Dicke, Phys. Rev. 93 1 99 (1954) Superradiant Rayliegh Scattering from a Bose Einstein Condensate S. Inouye, Science, 285 571 (1999) Cargese lecture notes W. Ketterle and S. Inouye: Collective enhancement and suppression in Bose-Einstein condensates. Compte rendus de l'académie des sciences, Série IV - Physique Astrophysique, vol. 2, pp. 339-380 (2001); e-print cond- mat/0101424.