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1. Spectroscopic study of the 4f ⁷ 6s ^{2 8} S 7/2∘ – 4f ⁷ ( ⁸ S ^° ) 6s6p( ¹ P ^° ) ⁸ P _5/2,7/2 transitions in neutral europium-151 and europium-153: absolute frequency and hyperfine structure

   https://doi.org/10.1364/JOSAB.521181  

   Maruko, C.; Çölmek, N_N; Herd, M_T; Ahrendsen, K_J; Cabrales, B.; Cannon, G.; Davis, E.; Guo, X_Y; Karani, T.; Wallace, A.; et al (April 2024, Journal of the Optical Society of America B)

   We report on spectroscopic measurements on the 4f⁷6s²⁸S_7/2^∘−4f⁷(⁸S^∘)6s6p(¹P^∘)⁸P_5/2,7/2transitions at 466.32 nm and 462.85 nm, respectively, in neutral europium-151 and europium-153. The center of gravity frequencies for the 151 and 153 isotopes for both transitions are reported for the first time using saturated absorption spectroscopy. For the 6s6p(¹P^∘)⁸P_5/2state, the center of gravity frequencies were found to be 642,894,493.3(4) MHz and 642,891,693.3(9) MHz for the 151 and 153 isotopes, respectively. The hyperfine constants for the upper state were found to beA(151)=−157.01(3)MHz,B(151)=74.5(4)MHz andA(153)=−69.43(14)MHz,B(153)=191.0(26)MHz. These hyperfine values are all consistent with previously published results except forB(151) that has a small discrepancy. The isotope shift was found to be 2799.54(20) MHz, a small discrepancy with previously published results. For the 6s6p(¹P^∘)⁸P_7/2state, the center of gravity frequencies were found to be 647,708,930.6(6) MHz and 647,705,958.4(26) MHz for the 151 and 153 isotopes, respectively. The hyperfine constants for the upper state were found to beA(151)=−218.66(4)MHz,B(151)=−293.4(8)MHz andA(153)=−97.15(13)MHz,B(153)=−750(3)MHz. These values are all consistent with previously published results except forA(151) that has a small discrepancy. The isotope shift was found to be 2972.8(5) MHz, a small discrepancy with previously measured results. 

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2. 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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3. Spectroscopic characterization of buffer-gas-cooled lead monofluoride molecules in the B 2Σ+(υ’ = 0) ← X1 2Π1/2(υ = 0) transition

   https://doi.org/10.1016/j.saa.2024.125508  

   Wang, Zesen; Pang, Renjun; Ma, Jie; Lin, Qinning; Hou, Shunyong; Wang, Hailing; Li, Xiaohu; Xu, Liang; Li, Xingjia; Chen, Guanglong; et al (March 2025, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy)

   Establishing a nonzero measurement of the electron Electric Dipole Moment (eEDM) has long been a fundamental pursuit in atomic, molecular and optical physics, offering possible insights into new physics beyond the Standard Model. In this regard, lead monofluoride (PbF) has emerged as a potential candidate for measuring eEDM primarily due to its suitable properties such as the strong internal effective electric field, and eEDM-sensitive ground state with large Ω-doubling and small magnetic g factor. In the present work, we realized the production of a buffer-gas-cooled PbF molecular beam and characterized its high-resolution spectroscopy in the B 2Σ+(υ’=0) ← X1 2Π1/2(υ = 0) transition, including both direct absorption and laser-induced fluorescence spectroscopy. A highly concentrated beam of PbF molecules is obtained with a central forward velocity of 223 ± 17 m/s, while 81, 66 and 24 hyperfine-structure-resolved spectral lines with a frequency accuracy of 40 MHz have been assigned respectively for 208PbF, 207PbF and 206PbF isotopologues. The hyperfine constants due to the 19F nucleus (A∥ and A⊥) of the B state are reported for the first time, and those of the 207Pb nucleus have been also updated. Such a cryogenic molecular beam of PbF in association with its hyperfine-structure-resolved spectral atlas of the B 2Σ+(υ’=0) ← X1 2Π1/2(υ = 0) transition will be essential in developing sensitive detection schemes towards the eEDM measurement. 

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4. Optical dipole trapping of Holmium

   Yip, Christopher; Booth, Donald; Zhou, Huaxia; Collett, Jeffrey; Saffman, Mark (May 2019, APS DAMOP meeting 2019)

   Neutral Holmium′s 128 ground hyperfine states, the most of any non-radioactive element, is a testbed for quantum control of a very high dimensional Hilbert space, and offers a promising platform for quantum computing. Its high magnetic moment also makes magnetic trapping a potentially viable alternative to optical trapping. Previously we have cooled Holmium atoms in a MOT on a 410.5 nm transition, characterized its Rydberg spectra, and made measurements of the dynamic scalar and tensor polarizabilities. We report here on progress towards narrow line cooling and magnetic trapping of single atoms. 

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5. Ammonia – Formic acid complex: internal rotation analysis, calculations, and new microwave measurements

   https://doi.org/10.1016/j.jms.2024.111884  

   Roehling, Kristen K; Hill, Rhett P; Daly, Adam M; Kukolich, Stephen G (February 2024, Journal of Molecular Spectroscopy)

   Heaven, Michael (Ed.)

   New analysis and spectra are reported for the gas-phase ammonia-formic acid complex. Calculations to deter- mine the theoretical barrier to internal rotation were conducted and led to the new internal rotation analysis of the dimer. Using the new analysis and calculations, 12 new lines were measured and assigned and included in the present analysis. This is the !rst internal rotation analysis for this complex. The measurements were made in the 7–22 GHz range using two Flygare-Balle type pulsed beam Fourier transform microwave (FTMW) spectrometers. The complex was analyzed as a hindered rotor and 20 A and 16 E state transitions were !t with the XIAM5 program. The rotational constants were determined to have the following values: A = 11970.19(9) MHz, B = 4331.479(4) MHz, and C = 3227.144(4) MHz. Rotational constants, quadrupole coupling constants, and internal rotor parameters were !t to the spectrum. Double resonance was used to verify line assignments and access higher frequencies. The barrier to internal rotation was found to be 195.18(7) cm 1. High level calculations are in good agreement with experimental values. The calculated V3 barrier values range from 168.3 to 212.8 cm 1. 

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