Observation of resonant electric dipole-dipole interactions between cold Rydberg atoms using microwave spectroscopy

This thesis reports the first observation of the resonant electric dipole-dipole interaction between cold Rydberg atoms using microwave spectroscopy, the observation of the magnetic field suppression of resonant interactions, and the development of a unique technique for precise magnetic field measurements.; A Rydberg state (46d5/2) of laser cooled 85Rb atoms has been optically excited. A fraction of these atoms has been transferred to another Rydberg state (47p3/2 or 45f5/2,7/2) to introduce resonant electric dipole-dipole interactions. The line broadening of the two-photon 46 d5/2--47d5/2 microwave transition due to the interaction of 46d5/2 with 47 p3/2 or 45f5/2,7/2 atoms has been used as a probe of the interatomic interactions. This experiment has been repeated with a DC magnetic field applied. The application of a weak magnetic field (≤ 0.6G) has reduced the line broadening due to the resonant electric dipole-dipole interaction, indicating that the interactions are suppressed by the field. Theoretical models have been developed that predict the energy shifts due to the resonant electric dipole-dipole interaction, and the suppression of interactions by magnetic fields. A novel technique for sensitive measurement of magnetic fields using the 34s1/2--34 p1/2 one-photon microwave transition has also been presented. Using this technique, it has been possible to calibrate magnetic fields in the magneto-optical trap (MOT) apparatus to less than 10mG, and put an upper bound of 17mG on any remaining field inhomogeneity.