Observation of an Isoscalar Resonance with Exotic J^{PC}=1^{-+} Quantum Numbers in J/ψ→γηη^{'}

Using a sample of (10.09±0.04)×10^{9}  J/ψ events collected with the BESIII detector operating at the BEPCII storage ring, a partial wave analysis of the decay J/ψ→γηη^{'} is performed. The first observation of an isoscalar state with exotic quantum numbers J^{PC}=1^{-+}, denoted as η_{1}(1855), is reported in the process J/ψ→γη_{1}(1855) with η_{1}(1855)→ηη^{'}. Its mass and width are measured to be (1855±9_{-1}^{+6})  MeV/c^{2} and (188±18_{-8}^{+3})  MeV, respectively, where the first uncertainties are statistical and the second are systematic, and its statistical significance is estimated to be larger than 19σ.

Pilot-Scale Synthesis Sodium Iron Fluorophosphate Cathode with High Tap Density for a Sodium Pouch Cell

Sodium-ion batteries (SIBs) have attracted wide interest for energy storage because of the sufficient sodium element reserve on the earth; however, the electrochemical performance of SIBs cannot achieve the requirements so far, especially, the limitation of cathode materials. Here, a kilogram-scale route to synthesize Na₂ FePO₄ F/carbon/multi-walled carbon nanotubes microspheres (NFPF@C@MCNTs) composite with a high tap density of 1.2 g cm^-3 is reported. The NFPF@C@MCNTs cathode exhibits a reversible specific capacity of 118.4 mAh g^-1 at 0.1 C. Even under 5 C with high mass loading (10 mg cm^-2 ), the specific capacity still maintains at 56.4 mAh g^-1 with a capacity retention rate of 97% after 700 cycles. In addition, a hard carbon||NFPF@C@MCNTs pouch cell is assembled and tested, which exhibits a volumetric energy density of 325 Wh L^-1 and gravimetrical energy density of 210 Wh kg^-1 (base on electrode massing), and it provides more than 200 cycles with a capacity retention rate of 92%. Furthermore, the pouch cell can operate in an all-climate environment ranging from -40 to 80 °C. These results demonstrate that the NFPF@C@MCNTs microspheres are a promising candidate cathode for SIBs and facilitate its practical application in sodium cells.

Observation of an a_{0}-like State with Mass of 1.817 GeV in the Study of D_{s}^{+}→K_{S}^{0}K^{+}π^{0} Decays

Using e^{+}e^{-} annihilation data corresponding to an integrated luminosity of 6.32  fb^{-1} collected at center-of-mass energies between 4.178 and 4.226 GeV with the BESIII detector, we perform the first amplitude analysis of the decay D_{s}^{+}→K_{S}^{0}K^{+}π^{0} and determine the relative branching fractions and phases for intermediate processes. We observe an a_{0}-like state with mass of 1.817 GeV in its decay to K_{S}^{0}K^{+} for the first time. In addition, we measure the ratio {B[D_{s}^{+}→K[over ¯]^{*}(892)^{0}K^{+}]/B[D_{s}^{+}→K[over ¯]^{0}K^{*}(892)^{+}]} to be 2.35_{-0.23stat}^{+0.42}±0.10_{syst}. Finally, we provide a precision measurement of the absolute branching fraction B(D_{s}^{+}→K_{S}^{0}K^{+}π^{0})=(1.46±0.06_{stat}±0.05_{syst})%.

Destabilization of the Charge Density Wave and the Absence of Superconductivity in ScV6Sn6 under High Pressures up to 11 GPa

RV6Sn6 (R = Sc, Y, or rare earth) is a new family of kagome metals that have a similar vanadium structural motif as AV3Sb5 (A = K, Rb, Cs) compounds. Unlike AV3Sb5, ScV6Sn6 is the only compound among the series of RV6Sn6 that displays a charge density wave (CDW) order at ambient pressure, yet it shows no superconductivity (SC) at low temperatures. Here, we perform a high-pressure transport study on the ScV6Sn6 single crystal to track the evolutions of the CDW transition and to explore possible SC. In contrast to AV3Sb5 compounds, the CDW order of ScV6Sn6 can be suppressed completely by a pressure of about 2.4 GPa, but no SC is detected down to 40 mK at 2.35 GPa and 1.5 K up to 11 GPa. Moreover, we observed that the resistivity anomaly around the CDW transition undergoes an obvious change at ~2.04 GPa before it vanishes completely. The present work highlights a distinct relationship between CDW and SC in ScV6Sn6 in comparison with the well-studied AV3Sb5.

Effect of the Interlayer Ordering on the Fermi Surface of Kagome Superconductor CsV_{3}Sb_{5} Revealed by Quantum Oscillations

The connection between unconventional superconductivity and charge density waves (CDWs) has intrigued the condensed matter community and found much interest in the recently discovered superconducting Kagome family of AV_{3}Sb_{5} (A=K, Cs, Rb). X-ray diffraction and Raman spectroscopy measurements established that the CDW order in CsV_{3}Sb_{5} comprises of a 2×2×4 structure with stacking of layers in a star-of-David (SD) and inverse-star-of-David (ISD) pattern along the c-axis direction. Such interlayer ordering will induce a vast normalization of the electronic ground state; however, it has not been observed in Fermi surface measurements. Here we report quantum oscillations of CsV_{3}Sb_{5} using tunnel diode oscillator frequency measurements. We observed a large number of frequencies, many of which were not reported. The number of frequencies cannot be explained by DFT calculations when only SD or ISD distortion is considered. Instead, our results are consistent with calculations when interlayer ordering is taken into account, providing strong evidence that the CDW phase of CsV_{3}Sb_{5} has complicated structure distortion which in turn has dramatic effects on the Fermi surface properties.

Distinct oxygen isotope fractionations driven by different electron donors during microbial nitrate reduction in lake sediments

Microbial nitrate reduction can be driven by organic carbon oxidation, as well as by inorganic electron donors, such as reduced forms of sulfur and iron. An apparent inverse oxygen isotope fractionation effect was observed during nitrate reduction in sediment incubations from five sampling sites of a freshwater lake, Hongze Lake, China. Incubations with organic and inorganic electron donor additions were performed. Especially, the inverse oxygen isotope effect was intensified after glucose addition, whereas the incubations with sulfide and Fe²⁺ showed normal fractionation factors. Nitrate reductase encoding genes, napA and narG, were analysed with metagenomics. Higher napA/narG ratios were associated with higher oxygen fractionation factors. The most abundant clade (59%) of NapA in the incubation with glucose was affiliated with Rhodocyclales. In contrast, it only accounted for 8%-9% of NapA in the incubations with sulfide and Fe²⁺ . Differences in nitrate reductases might explain different oxygen isotope effects. Our findings also suggested that large variance of O-nitrate isotope fractionations might have to be considered in the interpretation of natural isotope records.

Degradation of organic dye wastewater by H2O2-enhanced aluminum carbon micro-electrolysis

In this research, the treatment of methylene blue (MB) dye wastewater by a novel system that combines H₂O₂ with an aluminum-carbon micro-electrolysis (ACE) was explored. The effects of the H₂O₂ amount, initial pH, aluminum to carbon ratio, total aluminum-carbon mass, dye concentration, and reaction temperature on degradation of MB were investigated. The findings revealed that under the following conditions: H₂O₂ 34.0 mg/L, initial pH of 3.0, aluminum-to-carbon ratio of 2:1, total aluminum-carbon mass of 2.0 g/L, MB concentration of 20 mg/L, and 20 °C, the degradation rate of MB could reach 99.3% after 180 min, which is 18.4% more compared with ACE at the same conditions without H₂O₂. Through the quenching experiments, it was proved that the efficient free radicals produced during degradation are •OH and •O₂^-. Finally, a possible mechanism of H₂O₂ enhanced aluminum carbon micro-electrolysis (HP-ACE) for MB degradation was discussed.

Precise Measurements of Decay Parameters and CP Asymmetry with Entangled Λ-Λ[over ¯] Pairs

Based on 10 billion J/ψ events collected at the BESIII experiment, a search for CP violation in Λ decay is performed in the difference between CP-odd decay parameters α_{-} for Λ→pπ^{-} and α_{+} for Λ[over ¯]→p[over ¯]π^{+} by using the process e^{+}e^{-}→J/ψ→ΛΛ[over ¯]. With a five-dimensional fit to the full angular distributions of the daughter baryon, the most precise values for the decay parameters are determined to be α_{-}=0.7519±0.0036±0.0024 and α_{+}=-0.7559±0.0036±0.0030, respectively. The Λ and Λ[over ¯] averaged value of the decay parameter is extracted to be α_{avg}=0.7542±0.0010±0.0024 with unprecedented accuracy. The CP asymmetry A_{CP}=(α_{-}+α_{+})/(α_{-}-α_{+}) is determined to be -0.0025±0.0046±0.0012, which is one of the most precise measurements in the baryon sector. The reported results for the decay parameter will play an important role in the studies of the polarizations and CP violations for the strange, charmed and beauty baryons.

First Observation of the Direct Production of the χ_{c1} in e^{+}e^{-} Annihilation

We study the direct production of the J^{PC}=1^{++} charmonium state χ_{c1}(1P) in electron-positron annihilation by carrying out an energy scan around the mass of the χ_{c1}(1P). The data were collected with the BESIII detector at the BEPCII collider. An interference pattern between the signal process e^{+}e^{-}→χ_{c1}(1P)→γJ/ψ→γμ^{+}μ^{-} and the background processes e^{+}e^{-}→γ_{ISR}J/ψ→γ_{ISR}μ^{+}μ^{-} and e^{+}e^{-}→γ_{ISR}μ^{+}μ^{-} is observed by combining all the data samples. The χ_{c1}(1P) signal is observed with a significance of 5.1σ. This is the first observation of a C-even state directly produced in e^{+}e^{-} annihilation. The electronic width of the χ_{c1}(1P) resonance is determined to be Γ_{ee}=(0.12_{-0.08}^{+0.13})  eV, which is of the same order of magnitude as theoretical calculations.

Three-Dimensional Hierarchical Seaweed-Derived Carbonaceous Network with Designed g-C3N4 Nanosheets: Preparation and Mechanism Insight for 4-Nitrophenol Photoreduction

The development of g-C₃N₄-based photocatalysts with abundant active sites is of great significance for photocatalytic reactions. Herein, a smart and robust strategy was presented to fabricate three-dimensional (3D) g-C₃N₄ nanosheet-coated alginate-based hierarchical porous carbon (g-C₃N₄@HPC), including coating melamine on calcium alginate (CA) hydrogel beads, freeze-drying hydrogel beads as well as pyrolysis at high temperatures. The resulting photocatalyst possessed a significantly high surface area and a large amount of interconnected macropores compared with porous carbon without the melamine coating. The unique structural features could effectively inhibit the curling and agglomeration of g-C₃N₄ nanosheets, provide abundant photocatalytic active sites, and promote mass diffusion. Therefore, the g-C₃N₄@HPC composite exhibited remarkable photocatalytic activity and outstanding stability toward the photoreduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by NaBH₄ under natural sunlight and simulated visible-light irradiation (λ > 420 nm) using a 300 W xenon lamp. Moreover, the mechanism toward the photocatalytic reaction was extensively studied by quenching experiments and electron spin resonance (ESR) experiments. The results showed that active hydrogen species were able to be achieved by following a dual-channel pathway in the NaBH₄ system, which included photocatalytic reduction of H⁺ ions and photocatalytic oxidation of BH₄^- ions. This work not only opens up a new way to design efficient photocatalysts for various reactions but also provides a reference for an in-depth study of the photoreduction mechanism.

Evidence for a Neutral Near-Threshold Structure in the K_{S}^{0} Recoil-Mass Spectra in e^{+}e^{-}→K_{S}^{0}D_{s}^{+}D^{*-} and e^{+}e^{-}→K_{S}^{0}D_{s}^{*+}D^{-}

We study the processes e^{+}e^{-}→K_{S}^{0}D_{s}^{+}D^{*-} and e^{+}e^{-}→K_{S}^{0}D_{s}^{*+}D^{-}, as well as their charge conjugated processes, at five center-of-mass energies between 4.628 and 4.699 GeV, using data samples corresponding to an integrated luminosity of 3.8  fb^{-1} collected by the BESIII detector at the BEPCII storage ring. Based on a partial reconstruction technique, we find evidence of a structure near the thresholds for D_{s}^{+}D^{*-} and D_{s}^{*+}D^{-} production in the K_{S}^{0} recoil-mass spectrum, which we refer to as the Z_{cs}(3985)^{0}. Fitting with a Breit-Wigner line shape, we find the mass of the structure to be (3992.2±1.7±1.6)  MeV/c^{2} and the width to be (7.7_{-3.8}^{+4.1}±4.3)  MeV, where the first uncertainties are statistical and the second are systematic. The significance of the Z_{cs}(3985)^{0} signal is found to be 4.6σ including both the statistical and systematic uncertainty. We report the Born cross section multiplied by the branching fraction at different energy points. The mass of the Z_{cs}(3985)^{0} is close to that of the Z_{cs}(3985)^{+}. Assuming SU(3) symmetry, the cross section of the neutral channel is consistent with that of the charged one. Hence, we conclude that the Z_{cs}(3985)^{0} is the isospin partner of the Z_{cs}(3985)^{+}.

Transforming radical to non-radical pathway in peroxymonosulfate activation on nitrogen doped carbon sphere for enhanced removal of organic pollutants: Combined effect of nitrogen species and carbon structure

Carbon induced non-radical based peroxymonosulfate (PMS) activation has exhibited several advantages over radical process for eliminating organic pollutants in complicated water matrices. However, the relationship between configuration and composition of carbon and non-radical mechanism, which is important for designing high-efficiency carbon catalysts, remains elusive. In this work, the nitrogen doped carbon spheres (NCSs) with superior PMS activation ability were prepared from low-cost chitosan via two-step hydrothermal carbonization-pyrolysis method for organic pollutants removal. The carbon structure and nitrogen species of NCSs were tuned via changing hydrothermal temperature to explore their correlation with their PMS catalytic mechanism. Results showed hydrothermal carbonization boosted the content of pyridinic N, graphitic N and sp²-hybrided carbon (CC) in NCS, which significantly enhanced its catalytic performance and collaboratively promoted the catalytic mechanism switch from radical-dominant (SO₄^•- and •OH) to non-radical-dominant (surface-mediated electron transfer (SMET) and ¹O₂) process. The NCS with most pyridinic N and CC performed best, whose catalytic activity was 10.4 times higher than that without hydrothermal carbonization. The pyridinic N and CC enhanced the SMET process through strengthening PMS adsorption capacity and facilitating the electron migration from pollutant to PMS, respectively, while graphitic N triggered PMS oxidation on its neighboring electron-deficient C to produce ¹O₂.

Observation of Resonance Structures in e^{+}e^{-}→π^{+}π^{-}ψ_{2}(3823) and Mass Measurement of ψ_{2}(3823)

Using a data sample corresponding to an integrated luminosity of 11.3  fb^{-1} collected at center-of-mass energies from 4.23 to 4.70 GeV with the BESIII detector, we measure the product of the e^{+}e^{-}→π^{+}π^{-}ψ_{2}(3823) cross section and the branching fraction B[ψ_{2}(3823)→γχ_{c1}]. For the first time, resonance structure is observed in the cross section line shape of e^{+}e^{-}→π^{+}π^{-}ψ_{2}(3823) with significances exceeding 5σ. A fit to data with two coherent Breit-Wigner resonances modeling the sqrt[s]-dependent cross section yields M(R_{1})=4406.9±17.2±4.5  MeV/c^{2}, Γ(R_{1})=128.1±37.2±2.3  MeV, and M(R_{2})=4647.9±8.6±0.8  MeV/c^{2}, Γ(R_{2})=33.1±18.6±4.1  MeV. Though weakly disfavored by the data, a single resonance with M(R)=4417.5±26.2±3.5  MeV/c^{2}, Γ(R)=245±48±13  MeV is also possible to interpret data. This observation deepens our understanding of the nature of the vector charmoniumlike states. The mass of the ψ_{2}(3823) state is measured as (3823.12±0.43±0.13)  MeV/c^{2}, which is the most precise measurement to date.