Microwave Spectroscopy of High-L n=10 Rydberg Levels of Argon*

Using the RESIS/microwave method [1], we have determined the relative positions of the twenty fine structure levels with L $\ge $ 5 in the n=10 Rydberg manifold bound to the $^{2}$P$_{3/2}$ ground state of the Ar$^{+}$ ion. The typical measurement precision ($\pm $0.03 MHz) is approximately a factor of 1000 better than a recent study of similar levels by optical spectroscopy [2]. By comparing the measurements to the predictions of the long-range polarization model, several properties of the Ar$^{+}$ ion can be determined, including its scalar and tensor dipole polarizabilities, its quadrupole moment, and its g-factor. Also determined, but with less precision, are its quadrupole polarizability and its vector hyperpolarizability [3]. \newline [1] R.F. Ward, Jr., W.G. Sturrus, and S.R. Lundeen, Phys Rev. A \underline {53}, 113 (1996) \newline [2] L.E. Wright, E.L. Snow, S.R. Lundeen, and W.G. Sturrus, Phys. Rev. A \underline {75}, 022503 (2007) \newline [3] W. Clark, C.H. Greene, and G. Miecznik, Phys. Rev. A \underline {53}, 2248 (1996)