The charmonium-nucleon effective central interactions have been computed by the time-dependent HAL QCD method. This gives an updated result of a previous study based on the time-independent method, which is now known to be problematic because of the difficulty in achieving the ground-state saturation. We discuss that the result is consistent with the heavy quark symmetry. No bound state is observed from the analysis of the scattering phase shift; however, this shall lead to a future search of the hidden-charm pentaquarks by considering channel-coupling effects.
Properties of the wave function equivalent potentials introduced by HAL QCD collaboration are studied in a non-relativistic coupled-channel model. The derivative expansion is generalized, and then applied to the energy-independent and non-local potentials. The expansion coefficients are determined from analytic solutions to the Nambu-Bethe-Salpeter wave functions. The scattering phase shifts computed from these potentials are compared with the exact values to examine the convergence of the expansion. It is confirmed that the generalized derivative expansion converges in terms of the scattering phase shift rather than the functional structure of the non-local potentials. It is also found that the convergence can be improved by tuning either the choice of interpolating fields or expansion scale in the generalized derivative expansion.
Numerous biomimetic molecular catalysts inspired by methane
monooxygenases
(MMOs) that utilize iron or copper-oxo species as key intermediates
have been developed. However, the catalytic methane oxidation activities
of biomimetic molecule-based catalysts are still much lower than those
of MMOs. Herein, we report that the close stacking of a μ-nitrido-bridged
iron phthalocyanine dimer onto a graphite surface is effective in
achieving high catalytic methane oxidation activity. The activity
is almost 50 times higher than that of other potent molecule-based
methane oxidation catalysts and comparable to those of certain MMOs,
in an aqueous solution containing H2O2. It was
demonstrated that the graphite-supported μ-nitrido-bridged iron
phthalocyanine dimer oxidized methane, even at room temperature. Electrochemical
investigation and density functional theory calculations suggested
that the stacking of the catalyst onto graphite induced partial charge
transfer from the reactive oxo species of the μ-nitrido-bridged
iron phthalocyanine dimer and significantly lowered the singly occupied
molecular orbital level, thereby facilitating electron transfer from
methane to the catalyst in the proton-coupled electron-transfer process.
The cofacially stacked structure is advantageous for stable adhesion
of the catalyst molecule on the graphite surface in the oxidative
reaction condition and for preventing decreases in the oxo-basicity
and generation rate of the terminal iron-oxo species. We also demonstrated
that the graphite-supported catalyst exhibited appreciably enhanced
activity under photoirradiation owing to the photothermal effect.
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