Microwave spectroscopy of high-LRydberg states of neon

Sixteen fine-structure intervals separating n=10 neon Rydberg levels with L=5, 6, 7, and 8 were measured with the precision of about ±{}00.2 MHz, using fast beam microwave-optical techniques. The measured fine-structure pattern is in good agreement with the predictions of an effective potential model, and this comparison leads to precise determinations of the quadrupole moment and dipole polarizabilities of the ²{P}3/2$ ground state of the ${Ne}⁺$ ion: Q=-0.204 03(5)${ea}₀²$, ${{{α}}}ₛ$=1.3028(13)${a}₀³$, ${{{α}}}T$=-0.026(5)${a}₀³$. The contributions of magnetic interactions to the Rydberg fine structure lead to a determination of the ${Ne}⁺$ ion's g value, ${g}J$=1.354(21). All of these core parameters provide challenging tests of atomic structure calculations. The measurements also set a limit on the possible contributions to the fine structure due to a predicted geometric phase effect that is about an order of magnitude smaller than expected. {} 1996 The American Physical Society.