We observe an atomic ion's response to an electric quadrupole field to second and higher orders; this arises from the ion's electric quadrupole polarizability and hyperpolarizabilities. We probe a single ${}^{88}\mathrm{Sr}^{+}$ ion which is confined in the electric fields of a Paul trap and excited to Rydberg states. The quadrupolar trapping fields cause atomic energy level shifts and give rise to spectral sidebands. The effects on Rydberg $S_{1/2}$ states are described well by second-order perturbation calculations. The stronger effects on Rydberg $P_{1/2}$ states are captured by full diagonalization of the Hamiltonian.

中文翻译：

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观察二阶和更高阶电子四极杆与原子离子的相互作用

我们观察到原子离子对二阶和更高阶四极电场的响应；这是由离子的电四极极化率和超极化率引起的。我们探查单${}^{88}锶^{+}$离子被限制在保罗陷阱的电场中并激发到里德堡态。四极俘获场导致原子能级偏移并产生光谱边带。对里德堡的影响${秒}_{1/2}$通过二阶微扰计算很好地描述了状态。对里德堡的更强影响${磷}_{1/2}$ 通过哈密顿量的完全对角化来捕获状态。