Stagnancy of the pygmy dipole resonance

The pygmy dipole resonance(PDR) of nickel isotopes is studied using the deformed random phase approximation method. The isoscalar character of the pygmy resonance is confirmed, and the correlation between the pygmy resonance and neutron skin thickness is discussed. Our investigation shows a linear correlation between PDR integral cross section and neutron skin thickness when the excess neutrons lie in pf orbits, with a correlation rate of about 0.27 fm~(-1). However, in more neutron-rich nickel isotopes, the growth of the pygmy dipole resonance is stagnant. Although the neutron skin thickness increases, the whole skin is not active. There is an inertial part in the nuclei~(70-78)Ni which does not participate in the pygmy resonance actively and as a result, contributes little to the photo-absorption cross section.     

不同含量CO2热处理气氛对完全液相法制备二甲醚催化剂性能的影响

二甲醚(DME)是重要的化工原料[1],在制药、喷雾剂、致冷剂等工业中有着广泛的用途.十六烷值高、燃烧污染小的特性也使其成为公认的绿色燃料[2].浆态床反应器由于具有优异的移热性能而成为低成本制DME最有前景的反应床型[3～5],但催化剂的稳定性差是制约其工业化应用的主要障碍.