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Journal of Physics B Atomic Molecular and Optical Physics

Hyperfine structure of extremely high Rydberg msnd1D2,3D1,3D2and3D3series in odd alkaline-earth isotopes

Jun-Qiang Sun, K. T. Lu, R. Beigang

Published Sep 28, 1989• 13 citations
Publisher

Abstract

The MQDT of hyperfine structure is greatly simplified in extremely high Rydberg states. A four (or three)-channel quantum defect model is derived for the hyperfine structure of extremely high Rydberg states of msnd configuration in odd alkaline-earth isotopes, in which the transformation matrix U i(F)i' is given analytically except for one parameter which measures the mixing of singlet 1 D 2 and triple 3 D 2 induced by spin-orbit interaction in even isotopes, and in which the four eigen quantum defects mu i' (i'=1, 2, 3, 4) are related to the quantum defects of the fine structure in even isotopes by mu i' =mod( delta i' ). This model has been used to interpret the observed sublevel structure of 5snd (n>100) configurations in 87 Sr. An excellent agreement between the theoretical and experimental results was achieved.

DOI
10.1088/0953-4075/22/18/010

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The MQDT of hyperfine structure is greatly simplified in extremely high Rydberg states. A four (or three)-channel quantum defect model is derived for the hyperfine structure of extremely high Rydberg states of msnd configuration in odd alkaline-earth isotopes, in which the transformation matrix U i(F)i' is given analytically except for one parameter which measures the mixing of singlet 1 D 2 and triple 3 D 2 induced by spin-orbit interaction in even isotopes, and in which the four eigen quantum defects mu i' (i'=1, 2, 3, 4) are related to the quantum defects of the fine structure in even isotopes by mu i' =mod( delta i' ). This model has been used to interpret the observed sublevel structure of 5snd (n>100) configurations in 87 Sr. An excellent agreement between the theoretical and experimental results was achieved.
In extremely high Rydberg states of odd alkaline-earth isotopes, the Fermi constant a ms is comparable to the energy separation between levels belonging to different principal quantum numbers n and hyperfine interactions dominate the structure of the levels. The multichannel quantum defect theory of fine structure has been developed and applied to hyperfine structure and thus the HFS can be analysed directly by MQDT. A two-channel quantum defect model for extremely high Rydberg msns 1 S 0 and msns 3 S 1 series in odd alkaline-earth isotopes for F=I is described. The U i(F)i matrix is given analytically and the relationship between the eigenquantum defects of HFS and the quantum defects of fine structure is derived. The HFS of two extremely high Rydberg 5sns 1 S 0 and 3 S 1 series in 87 Sr has been calculated by the model and an excellent agreement between the theoretical and experimental results has been achieved. The HFS of extremely high Rydberg msns 1 S 0 and 3 S 1 series in 43 Ca, 135 Ba and 137 Ba are also analysed by the model.
A combined experimental and theoretical spectroscopic study of high-$n, 30\ensuremath{\lesssim}n\ensuremath{\lesssim}100$, triplet SSS and DDD Rydberg states in 87Sr^{87}\mathrm{Sr}87Sr is presented. 87Sr^{87}\mathrm{Sr}87Sr has a large nuclear spin I=9/2I=9/2I=9/2, and at high-nnn the hyperfine interaction becomes comparable to, or even larger than, the fine structure and singlet-triplet splittings, which poses a considerable challenge both for precision spectroscopy and for theory. For high-nSn SnS states, the hyperfine shifts are evaluated nonperturbatively, taking advantage of earlier spectroscopic data for the I=0I=0I=0 isotope 88Sr^{88}\mathrm{Sr}88Sr, which results in good agreement with the present measurements. For the DDD states, this procedure is reversed by first extracting from the present 87Sr^{87}\mathrm{Sr}87Sr measurements the energies of the 3D1,2,3{}^{3}{D}_{1,2,3}3D1,2,3​ states to be expected for isotopes without hyperfine structure (88Sr^{88}\mathrm{Sr}88Sr), which allows the determination of corrected quantum defects in the high-nnn limit.
High-resolution two-photon spectroscopy was applied to investigate the msns 1S0^{1}S_{0}1S0​ Rydberg states of the alkaline-earth elements Ca, Sr, and Ba. It is shown for 43Ca^{43}\mathrm{Ca}43Ca, 87Sr^{87}\mathrm{Sr}87Sr, 135Ba^{135}\mathrm{Ba}135Ba, and 137Ba^{137}\mathrm{Ba}137Ba that the hyperfine interaction causes a level shift between odd- and even-mass isotopes. A theoretical interpretation is presented which relates the energy-level shift for odd isotopes to the singlet-triplet separation which in turn is a function of the principal quantum number, and good agreement with the experimental results is found.
The hyperfine structure of 6snd1D26snd^{1}D_{2}6snd1D2​ Rydberg states of 135,137Ba^{135,137}\mathrm{Ba}135,137Ba is reported for principal quantum numbers ranging between n=10n=10n=10 and n=50n=50n=50. From our data, singlet-triplet mixing coefficients have been deduced. A three-channel quantum-defect model has been used to analyze the resonance in singlet-triplet mixing of 6snd1D2and3D26snd^{1}D_{2} \mathrm{and} ^{3}D_{2}6snd1D2​and3D2​ Rydberg states in the vicinity of the 5d7d1D25d7d^{1}D_{2}5d7d1D2​ perturber. For the determination of the scattering matrix, hyperfine-structure data were found to be essential. Good agreement has been achieved between calculated and experimental singlet-triplet mixing coefficients.
The complex Rydberg structure of ytterbium atoms is shaped by multiple low-lying ion-core-excited states and strong channel interactions, which presents both opportunities and challenges for quantum information processing and precision metrology. In this work, we extend high-resolution microwave spectroscopy and multichannel quantum defect theory (MQDT) modeling of singly excited $6sn\ensuremath{\ell}$ Rydberg states in 174Yb^{174}\mathrm{Yb}174Yb and 171Yb^{171}\mathrm{Yb}171Yb to include the $\ensuremath{\ell}=3$ (fff) and $\ensuremath{\ell}=4$ (ggg) series. Our measurements reveal $p\text{\ensuremath{-}}f$ mixing in odd-parity Rydberg states of 171Yb^{171}\mathrm{Yb}171Yb, which we incorporate by combined MQDT models for 6snp6snp6snp and 6snf6snf6snf series. Additionally, we observe that for $\ensuremath{\ell}=4$ the spin-orbit interaction dominates over the exchange interaction, such that the 6sng6sng6sng states are more accurately described in a jjjjjj-coupled basis. We validate our models by comparing the predicted Land\'e ggg factors and static dipole polarizabilities with experimental measurements, finding excellent agreement. These results provide important input for designing high-fidelity entangling gates with ytterbium atoms.