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1. Measurement of the hyperfine coupling constants and absolute energies of the $12s {}^2{S}_{1/2}, 13s {}^2{S}_{1/2}$ , and $11d {}^2{D}_J$ levels in atomic cesium

   https://doi.org/10.1103/PhysRevA.105.022819  

   Quirk, Jonah A; Damitz, Amy; Tanner, Carol E; Elliott, D S (February 2022, Physical Review A)

   We report measurements of the absolute energies of the hyperfine components of the $$12s \ ^2S_{1/2}$$ and $$13s \ ^2S_{1/2}$$ levels of atomic cesium, $$^{133}$$Cs. Using the frequency difference between these components, we determine the hyperfine coupling constants for these states, and report these values with a relative uncertainty of $$\sim$$0.06\%. We also examine the hyperfine structure of the $$11d \ ^2D_{J}$$ ($J=3/2, 5/2$) states, and resolve the sign ambiguity of the hyperfine coupling constants from previous measurements of these states. We also derive new, high precision values for the state energies of the $$12s \ ^2S_{1/2}$$, $$13s \ ^2S_{1/2}$$ and $$11d \ ^2D_{J}$$ states of cesium. 

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2. High-precision measurement of the $2s2p{}^{1}P_1^o$ center of gravity in neutral ${}^9\mathrm{Be}$ at the parts-per-billion level

   https://doi.org/10.1103/8b1f-fpgq  

   Ahrendsen, K J; Kay, E M; Williams, W D (July 2025, Physical Review A)

   We use saturated absorption spectroscopy to study neutral ^9Be atoms produced in a dc discharge lamp. Previous measurements of the 2s2p^1P^o_1 state energy were limited in precision due to overlapping hyperfine structure. In this work, we apply a 400 G magnetic field, which splits the magnetic sublevels creating a spectral feature near the center-of-gravity energy of the state. We determine the transition frequency from the ground state to be 1276080105.5(1.2) MHz, corresponding to a center-of-gravity energy of 42565.45058(4) cm−1. This result is a factor of 30 more precise than the previous best measurement and constitutes the most precise determination of an excited-state energy in a four-electron system to date. As theoretical methods advance, this result will enable stringent tests of quantum electrodynamics in four-electron systems. 

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3. Direct measurement of the $7s{}^2{S}_{1/2}\to 7p{}^2{P}_{3/2}$ transition frequency in ${}^{226}\mathrm{Ra}^{+}$

   https://doi.org/10.1103/PhysRevA.102.042822  

   Holliman, C. A.; Fan, M.; Contractor, A.; Straus, M. W.; Jayich, A. M. (October 2020, Physical Review A)

   null (Ed.)
4. Measurement of the ratio of the scalar polarizability to the vector polarizability for the $6s{}^{2}S_{1/2}\to 7s{}^{2}S_{1/2}$ transition in cesium

   https://doi.org/10.1103/PhysRevA.109.062809  

   Quirk, Jonah A; Tanner, Carol E; Elliott, D S (June 2024, Physical Review A)

   We report measurements of the ratio of the scalar polarizability $$\alpha$$ to the vector polarizability $$\beta$$ for the $$6s ^2S_{1/2} \rightarrow 7s ^2S_{1/2}$$ transition in atomic cesium. These measurements are motivated by a discrepancy between the values of the vector transition polarizability as determined using two separate methods. In the present measurement, we use a two-pathway, coherent-control technique in which we observe the interference between a two-photon interaction driven by infrared light at 1079 nm and a linear Stark-induced interaction driven by the mutually-coherent second harmonic of this infrared beam at 540 nm. The result of our measurements is $$\alpha/\beta = -9.902 \: (9)$$, in good agreement with the previous determination of this ratio. This measurement, critical to the study of atomic parity violation in cesium, does not reduce the discrepancy between the two methods for the determination of the vector polarizability $$\beta$$ for this transition. 

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5. Observation of a $\mu \text{s}$ isomer in ${}_{49}{}^{134}\mathrm{In}_{85}$ : Proton-neutron coupling “southeast” of ${}_{50}{}^{132}\mathrm{Sn}_{82}$

   https://doi.org/10.1103/PhysRevC.100.011302  

   Phong, V. H.; Lorusso, G.; Davinson, T.; Estrade, A.; Hall, O.; Liu, J.; Matsui, K.; Montes, F.; Nishimura, S.; Boso, A.; et al (July 2019, Physical Review C)