Pseudoscalar meson and baryon octet interaction with strangeness zero in the unitary coupled-channel approximation

The interaction of the pseudoscalar meson and the baryon octet is investigated by solving the Bethe-Salpeter equation in the unitary coupled-channel approximation. In addition to the Weinberg-Tomozawa term, the contribution of the s-and u-channel potentials in the-wave approximation are taken into account. In the sector of isospin I=1/2 and strangeness S =0, a pole is detected in a reasonable region of the complex energy plane of ■ in the center-of-mass frame by analyzing the behavior of the scattering amplitude, which is higher than the ηN threshold and lies on the third Riemann sheet. Thus, it can be regarded as a resonance state and might correspond to the N(1535) particle of the Particle Data Group(PDG) review. The coupling constants of this resonance state to the πN,ηN,KΛ and KΣ channels are calculated, and it is found that this resonance state couples strongly to the hidden strange channels. Apparently, the hidden strange channels play an important role in the generation of resonance states with strangeness zero. The interaction of the pseudoscalar meson and the baryon octet is repulsive in the sector of isospin I = 3/2 and strangeness S = 0, so that no resonance state can be generated dynamically.     

The D~* interaction with isospin zero in an extended hidden gauge symmetry approach

The D~* interaction via a ρ or ω exchange is constructed within an extended hidden gauge symmetry approach, where the strange quark is replaced by the charm quark in the SU(3) flavor space. With this D~*interaction, a bound state slightly lower than the D~* threshold is generated dynamically in the isospin zero sector by solving the Bethe-Salpeter equation in the coupled-channel approximation, which might correspond to the X(3872)particle announced by many collaborations. This formulism is also used to study the BB~* interaction, and a BB~* bound state with isospin zero is generated dynamically, which has no counterpart listed in the review of the Particle Data Group. Furthermore, the one-pion exchange between the D meson and the ~* is analyzed precisely, and we do not think the one-pion exchange potential need be considered when the Bethe-Salpeter equation is solved.     

外场作用下吡咯分子的物理性质研究

吡咯分子是重要的有机半导体材料，适用于微电子和光电等多个领域，成功地引领了一场新的技术革命.本文基于密度泛函理论，使用B3LYP/6-311++g (d,p)方法研究了在0-0.03 a.u.的电场强度作用下，吡咯分子的物理特性变化规律.发现随着电场的增大，分子逐渐沿x轴方向被压缩，分子的偶极矩在减小，总能量在减小.分子的最高占据分子轨道能量基本保持不变，最低未占据分子轨道能量在不断地下降，致使分子的能带隙不断减小，无法保证能带隙的稳定性，从而降低了半导体材料的使用寿命.通过含时密度泛函计算可以发现:在不同的电场下，吡咯分子均出现两个紫外吸收峰，其中两个C=C双键的π-π^*跃迁占主要贡献.但随着电场强度的增大，其在跃迁中的占比越来越小.考察在0.02 a.u.的电场下，紫外吸收峰主要由第6、11、13、15等激发态决定.这为更好地研究和设计半导体材料提供了良好的理论依据.