Probabilities for electric quadrupole transitions between Rydberg states of atoms and ions

Gerard T. Higgins, Chi Zhang, Fabian Pokorny +4 more

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 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.

Jianing Han

Jiajia Zha, Zhihao Qin, Jiayi Yan +3 more

Using a method based on the Magnus expansion, the survival of Rydberg atoms in intense laser fields is studied. Usually, for atoms in intense laser fields, effects beyond the electric dipole approximation need to be considered. In the past few years, researchers have primarily paid attention to the nondipole effects induced by the electric quadrupole term of the optical field. The quadrupole term plays a more important role than the electric dipole term in the calculation of the survival probability of Rydberg atoms in intense laser fields even though the magnitude of the former is smaller than that of the latter in terms of the multipole expansion of the optical vector potential. Meanwhile, the effects of higher-order corrections beyond the quadrupole term remain ambiguous. In this paper, we confirm that corrections containing higher-order terms, except for the quadrupole term, can be neglected in the calculation of the transitions of Rydberg atoms in external fields. We then use the second-order time evolution operator containing the quadrupole term to study the scaling law of the transition probability of Rydberg He in laser fields with different parameters.

S. Feneuille, P. Jacquinot

Thomas F. Gallagher, P. Pillet

Leping Li, Quanli Gu, Joseph L. Knee +3 more

We report the observation of an electric quadrupole transition between the 4s′[1/2]o0 and 3d[3/2]o2 states in the spectrum of argon and use it in the first step of a scheme to excite Rydberg states. The initial identification of the transition is based on one-color, two-photon photoionization. A different experiment utilizing two-color, two-photon photoexcitation to Rydberg states confirms the identification. Despite the unavoidable background of one-color, two-photon photoionization, the latter experimental technique makes possible two-photon spectroscopy of Rydberg states using a resonant intermediate state populated by an electric quadrupole transition.