Mingkai Fu

Dynamical importance of van der Waals saddle and excited potential surface in C( 1 D )+D 2 complex-forming reaction

Encouraged by recent advances in revealing significant effects of van der Waals wells on reaction dynamics, many people assume that van der Waals wells are inevitable in chemical reactions. Here we find that the weak long-range forces cause van der Waals saddles in the prototypical C(1D)+D2 complex-forming reaction that have very different dynamical effects from van der Waals wells at low collision energies. Accurate quantum dynamics calculations on our highly accurate ab initio potential energy surfaces with van der Waals saddles yield cross-sections in close agreement with crossed-beam experiments, whereas the same calculations on an earlier surface with van der Waals wells produce much smaller cross-sections at low energies. Further trajectory calculations reveal that the van der Waals saddle leads to a torsion then sideways insertion reaction mechanism, whereas the well suppresses reactivity. Quantum diffraction oscillations and sharp resonances are also predicted based on our ground- and excited-state potential energy surfaces.

Synthesis of asymmetric dendrimers with controllable chromophore concentration and improved electro-optical performance

In this work, we firstly provided a simple work-up procedure to prepare a new kind of electro-optical dendrimer with an asymmetric configuration via a Cu-(I) catalyzed Huisgen-reaction. The resulting NLO dendrimers exhibited both good thermal stability and good film-forming ability. In order to investigate the influence of the asymmetric configuration on the electro-optic (EO) activities, UV-vis spectra, density functional theory (DFT) calculations and EO performance were studied. Due to their asymmetric spherical structure, two dendrimers showed weak dipole–dipole aggregation compared with traditional dendritic electro-optical materials (DESD), but they achieved better alignment after each poling process was carried out. As expected, HJ-2 exhibited 41 pm V−1 in an EO coefficient test, which was higher than DESD and the guest–host polymeric system (C2 + PMMA) using the same chromophores.

Laser cooling of copper monofluoride: a theoretical study including spin–orbit coupling

The feasibility of direct laser cooling of copper monofluoride (CuF) is investigated and assessed using ab initio methods with the inclusion of spin–orbit coupling (SOC) effects. Seven low-lying Λ–S states are calculated using an explicitly correlated multireference configuration interaction method with the Davidson correction (MRCI-F12 + Q). The spectroscopic properties of the Ω states are calculated, which are in very good agreement with the available experimental measurements and indicate that the influence of SOC effects is evident. We find that, the radiative lifetimes of transitions A(ν′ = 0) → a3Σ+1, b3Π1,0+ are much longer than that of the A(ν′ = 0) → X(ν = 0) transition; the vibrational branching ratios Rν′ν for the A(ν′) ← X(ν) transition are highly diagonally distributed with R00 being 0.991; and the evaluated transition wavelengths are located in the visible region. We further propose a laser cooling scheme based on the A(ν′) ← X(ν) transition, with which the laser cooling of CuF can be realized effectively. Moreover, a photoionization method is suggested for the magneto-optical trap detection of CuF.

Asymmetric dendrimers with improved electro-optic performance: synthesis and characterization

A new series of electro-optical dendrimers with asymmetric configurations was synthesized through a Cu-(I) catalyzed Huisgen reaction. The asymmetric dendrimers exhibited weaker chromophore dipole–dipole aggregations along with an improved response to the applied poling field than traditional dendrimers with the same type of chromophores. In order to systematically investigate the influence of the asymmetric structure on the physical properties, UV-vis spectroscopy and DFT calculations were carried out. Due to the asymmetric configurations, the obtained dendrimers exhibited weak dipole–dipole interactions compared with dendrimers with a flexible linker, furthermore they obtained a better alignment in the poling process. The asymmetric dendrimer AD-2 exhibited a 36 pm V−1 EO coefficient measurement, which was higher than the other two dendrimers and guest–host polymeric materials using the same chromophores.