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Abstract Based on a template-matching method, we estimate the barium (Ba) abundances for stellar spectra from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Medium-Resolution Spectroscopic Survey (MRS). The Ba abundances of 198,011 stars have been determined from MRS spectra with signal-to-noise ratios (S/N) > 40 combined with the stellar atmospheric parameters from the LAMOST Low-Resolution Spectroscopic Survey DR9 by the LAMOST Stellar Parameter Pipeline. The uncertainties in the Ba abundances from the LAMOST MRS spectra are less than 0.3 dex when S/N exceeds 40, which align closely with the results based on the high-resolution UVES spectra from the Gaia-ESO survey obtained by spectral synthesis. Further analysis of Ba abundances from repeated observations of the same stars reveals that random errors related to spectral quality remain below 0.3 dex at the same S/N, with a systematic overestimation for the low-S/N spectra. This extensive sample of stellar Ba abundances will enhance studies of thes-,i-, andr-processes, and deepen our understanding of the chemical-evolution history of the Milky Way. 

Abstract R-process-enhanced (RPE) stars are rare and typically metal-poor ([Fe/H]  < −1.0), primarily found in the Milky Way halo system and dwarf galaxies. This study reports the discovery of two relatively bright, highly RPE stars ([Eu/Fe]  >  +0.70) located in the Milky Way disk, with [Fe/H] of −0.34 and −0.80, respectively. These two stars are selected from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope medium-resolution (R ∼ 7500) spectroscopic survey. Follow-up high-resolution (R ∼ 25,000) observations were conducted with the High Optical Resolution Spectrograph installed on the 10.4 m Gran Telescopio Canarias. We perform the determination of elemental abundances and calculate the orbital parameters. We find that they arer-II stars with elemental abundances in agreement with the solarr-process pattern. These two objects are chemically and dynamically consistent with membership in the Galactic disk and exhibit no evidence of being part of accreted systems. 

Abstract Highlyr-process-enhanced (RPE) stars are rare and usually metal poor ([Fe/H] < −1.0), and they mainly populate the Milky Way halo and dwarf galaxies. This study presents the discovery of a relatively bright (V= 12.72), highly RPE (r-II) star ([Eu/Fe] = +1.32, [Ba/Eu] = −0.95), LAMOST J020623.21+494127.9. This star was selected from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope medium-resolution (R∼ 7500) spectroscopic survey; follow-up high-resolution (R∼ 25,000) observations were conducted with the High Optical Resolution Spectrograph installed on the Gran Telescopio Canarias. The stellar parameters (T_eff= 4130 K, $\log \mathrm{g}$= 1.52, [Fe/H] = −0.54,ξ= 1.80 km s⁻¹) have been inferred taking into account nonlocal thermodynamic equilibrium effects. The abundances of [Ce/Fe], [Pr/Fe], and [Nd/Fe] are +0.19, +0.65, and +0.64, respectively, relatively low compared to the Solarr-process pattern normalized to Eu. This star has a high metallicity ([Fe/H] = −0.54) compared to most other highly RPE stars and has the highest measured abundance ratio of Eu to H ([Eu/H] = +0.78). It is classified as a thin-disk star based on its kinematics and does not appear to belong to any known stream or dwarf galaxy. 

Two seven-coordinate mononuclear Co(ii) complexes are proved to have field-induced magnetic relaxation and one of them possesses capped octahedral geometry. 

Three mononuclear tetrakis(pseudohalido)-cobalt( ii ) complexes (Ph 4 P) 2 [Co(E) 4 ] (E = N 3 − , 1; NCO − , 2; NCS − , 3) have been synthesized and structurally characterized. Each compound contains a distorted tetrahedral Co 2+ ion coordinated by four pseudohalide ligands. The magnetic properties of 1–3 have been studied using direct-current magnetic measurements and high-frequency and -field EPR spectroscopy (HFEPR), suggesting easy-axis magnetic anisotropy for 1 and 2 and easy-plane anisotropy for 3. Analysis of the HFEPR spectra yielded D values of −5.23 and +3.63 cm −1 for 2 and 3, respectively. The absence of the EPR signal in 1 is consistent with a large, negative value of the zero-field splitting (ZFS) parameter D in 1. The nature of magnetic anisotropies of 1–3 has also been confirmed by ab initio calculations. The calculated D values are consistent with those determined using magnetometry and HFEPR studies. Alternating current (AC) magnetic susceptibilities reveal slow magnetic relaxation under an applied magnetic field, thus indicating that 1–3 are field-induced single-ion magnets (SIMs).