April, 2006

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Chiral Switch Using Wholly Achiral Molecules Achieved

Recently, Prof. Liu Minghua and his group from the Institute of Chemistry, Chinese Academy of Sciences, have investigated the interfacial organization behaviors of an achiral molecule, 5-(octadecyloxy)-2-(2-thiazolylazo)phenol (TARC18), at the air/water interface. They have found that the intrinsically achiral TARC18 can form two different chiral supramolecular assemblies under the same conditions by chance, which has been confirmed by UV-vis and FTIR spectra.  However, there is a correlation between the CD spectra and the films. That is, one type of the chiral films always shows a positive Cotton effect while another one shows a negative Cotton effect. It is more interesting to find that the chirality of the TARC18 films can be destroyed by exposing the film to HCl gas, and is then subsequently recovered in air. The number of repeat cycles has been extended to more than ten times and thus a reversible chiroptical switch is achieved. This is maybe the first time to construct the chiral switch based on the achiral building blocks. The relevant research results were recently published in Advanced Materials , 177-180, 18, 2006.

Chinese Scientists Proposes Proper Definition of Spin Current

Recently, Shi Junren, research fellow from the Condensed Theory and Material Computation Laboratory, Institute of Physics, CAS, Zhang Ping research fellow from Beijing Institute of Applied Physics and Computational Mathematics, professor Niu Qian and his PhD graduate Xiao Di from the University of Texas at Austin jointly studied the concept of spin current and corrected its traditional definition. They proposed that spin current should be defined as the time derivative of the spin displacement (product of spin and position observables). Only such definition can satisfy the basic requirement of non-equilibrium thermodynamics, thus can be directly measured in lab. This solves a basic problem in the Spintronics field and is of great importance to future research. The results were published in US Physics Review Letter (96, 076604, 2006).-9

Science Publishes New Result on Resonance Research

Recently, Science published a paper entitled ˇ°Observation of Feshbach Resonances in the F+H2 -> HF+H Reactionˇ± co-authored by Research Professors Yang Xueming, Qiu Minghui, Ren Zefeng, Che Li, Dai Dongxu, Wang Xiuyan, and Zhang Donghui etc. from the Dalian Institute of Chemical Physics, CAS. This new discovery shows that distinct forward-scattered HF products in the v'=2 vibrational state were clearly observed at a collision energy of 0.52 kcal/mol; this was attributed to both the ground and the first excited Feshbach resonances trapped in the peculiar HF (v'=3)-H vibrationally adiabatic potential, with substantial enhancement by constructive interference between the two resonances.-10

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