Using a sample of 3.8 M (2S) events accumulated with the BES detector, the process (2S) → ϩ Ϫ J/ is studied. The angular distributions are compared with the general decay amplitude analysis of Cahn. We find that the dipion system requires some D wave amplitude, as well as S wave. On the other hand, the J/Ϫ(ϩ Ϫ) relative angular momentum is consistent with being pure S wave. The decay distributions have been fit to heavy quarkonium models, including the Novikov-Shifman model. This model, which is written in terms of the parameter , predicts that D wave pions should be present. We determine ϭ0.183 Ϯ0.002Ϯ0.003 based on the joint m Ϫcos * distribution. The fraction of D wave amplitude as a function of m is found to decrease with increasing m , in agreement with the model. We have also fit the Mannel-Yan model, which is another model that allows D wave pions.
The decays of the c͑2S͒ into vector plus tensor meson final states have been studied for the first time using the BES detector. We determine upper limits on branching fractions for c͑2S͒ decays into vf 2 , ra 2 , K 0ء K 0ء 2 1 c.c., and ff 0 2 ͑1525͒ that are, in each case, significantly smaller than the corresponding branching fractions for the J͞c meson, scaled according to the expectations of perturbative QCD.[S0031-9007(98)07836-3]
We propose an effective highest occupied d‐orbital modulation strategy engendered by breaking the coordination symmetry of sites in the atomically precise Cu nanocluster (NC) to switch the product of CO2 electroreduction from HCOOH/CO to higher‐valued hydrocarbons. An atomically well‐defined Cu6 NC with symmetry‐broken Cu−S2N1 active sites (named Cu6(MBD)6, MBD=2‐mercaptobenzimidazole) was designed and synthesized by a judicious choice of ligand containing both S and N coordination atoms. Different from the previously reported high HCOOH selectivity of Cu NCs with Cu−S3 sites, the Cu6(MBD)6 with Cu−S2N1 coordination structure shows a high Faradaic efficiency toward hydrocarbons of 65.5 % at −1.4 V versus the reversible hydrogen electrode (including 42.5 % CH4 and 23 % C2H4), with the hydrocarbons partial current density of −183.4 mA cm−2. Theoretical calculations reveal that the symmetry‐broken Cu−S2N1 sites can rearrange the Cu 3d orbitals with
as the highest occupied d‐orbital, thus favoring the generation of key intermediate *COOH instead of *OCHO to favor *CO formation, followed by hydrogenation and/or C−C coupling to produce hydrocarbons. This is the first attempt to regulate the coordination mode of Cu atom in Cu NCs for hydrocarbons generation, and provides new inspiration for designing atomically precise NCs for efficient CO2RR towards highly‐valued products.
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