A hearty congratulations is extended to Professor Michael Shay who has just been elected a Fellow of the American Physical Society. The citation, which will appear on his Fellowship Certificate, will read: “For pioneering contributions to understanding magnetic reconnection, including the nature of collisionless reconnection, and of plasma turbulence.” This is a great achievement - it is limited to no more than one half of one percent of the membership.
The minimal-coupling Hamiltonian describing the interaction between an atom and a light field includes an A·p term, which is employed in spectroscopy, and an A·A term, which is relevant in light scattering. Here it is shown that the A·A term can be employed in high-precision atomic spectroscopy by providing a strong spatial variation of the field intensity within the volume of the atom, and by modulating the field intensity in time at the atomic transition frequency of interest. These requirements are satisfied for Rydberg atoms trapped in an intensity-modulated optical lattice . Selection rules in this type of spectroscopy are greatly relaxed in comparison with the standard selection rules, allowing access to previously forbidden transitions [2, 3]. We have demonstrated the new spectroscopy by scanning the light modulation frequency over a Rydberg-atom resonance and probing the population in the target Rydberg state . More recently, we have driven transitions at higher harmonics of the drive; this provides convenient access to sub-Terahertz transitions between Rydberg levels. Further, we have shown that optical-lattice Rydberg atom traps support “magic” transitions .
In a second experiment with Rydberg atoms in an optical lattice, we employ doubly-resonant two-photon excitation into the 74S Rydberg state to spectroscopically measure the dynamic scalar and tensor polarizabilities of the rubidium 5P3/2 level . To reach the necessary high intensities, we employ a cavity-generated 1064-nm optical-lattice light field, allowing us to obtain intensities near 2x1011 W/m2. In the evaluation of the data we use a self-referencing method that renders the polarizability measurement largely free from the intensity calibration of the laser light field. We obtain experimental values of -1149 +/- 2.5% and 563 +/- 4.2% for the scalar and tensor parts, in atomic units.
 S. E. Anderson, K. C. Younge, G. Raithel, Phys. Rev. Lett. 107, 263001 (2011).
 B. Knuffman and G. Raithel, Phys. Rev. A 75, 053401 (2007).
 K. R. Moore, S. E. Anderson, G. Raithel, Nature Communications 6 (2015).
 K. Moore, G. Raithel, “Nonlinear and magic ponderomotive spectroscopy,” arXiv:1506.01761 (2015).
 Y.-J. Chen, L. F. Gonçalves, G. Raithel, “Measurement of Rb 5P3/2 scalar and tensor polarizabilities in a 1064 nm light field,” arXiv:1507.05675 (2015).