氢负离子在电介质球面附近的光剥离研究∗

摘要

Photodetachment of hydrogen negative ion near a dielectric sphere has been studied by using the image method combined with the semiclassical closed orbit theory. Firstly, we analyze the image charge distribution of the detached electron near the dielectric sphere; then we put forward the Hamiltonian for this system. By solving the Hamiltonian canonical equations, we can find the closed orbits of the detached electrons moving near the dielectric sphere. With the help of the semiclassical closed orbit theory, we derive the formula for calculating the photodetachment cross section of this system. Then we can calculate and analyze the photodetachment cross section. Calculated results suggest that the photodetachment cross section of the hydrogen negative ion near a dielectric sphere is not only related to the photon energy, but also the dielectric constant of the sphere. For a given dielectric sphere, with the increase of photon energy, the oscillating amplitude in the photodetachment cross section decreases while the oscillation frequency increases. When the photon energy is increased to a critical value, the oscillating structures in the cross section disappear. In addition, with the increase in the dielectric constant of the dielectric sphere, the oscillating structure in the photodetachment cross section becomes much more complicated. When the dielectric constant is increased to infinity, the photodetachment cross section of this system is consistent with the photodetachment cross section of the hydrogen negative ion near a metal sphere. Therefore, we can control the photodetachment cross section of the hydrogen negative ion near a dielectric sphere by changing the photon energy and the dielectric constant. Our study may provide some theoretical guidance and reference values for the experimental research of photodetachment of negative ion near the dielectric sphere.%利用镜像法结合半经典闭合轨道理论，对氢负离子在电介质球面附近的光剥离进行了研究。首先利用镜像法分析了剥离电子在电介质球内的镜像电荷分布情况，然后给出了体系的哈密顿量。通过求解哈密顿正则方程，找到了剥离电子在电介质球面附近运动时的闭合轨道。借助于半经典闭合轨道理论，推导出了体系的光剥离截面，并且对光剥离截面进行了计算和分析。计算结果表明，氢负离子在电介质球面附近的光剥离截面不仅与入射光子的能量有关，而且还与电介质球面的介电常数有关。对于给定的电介质球面，随着入射光子的能量增加，光剥离截面的振荡振幅减小、振荡频率增加。当入射光子的能量增加到某一临界值时，光剥离截面的振荡结构消失。除此之外，随着电介质球面介电常数的增大，光剥离截面的振荡结构变得更加复杂。当电介质常数增大到无穷大时，体系的光剥离截面和氢负离子在金属球面附近的光剥离截面一致。因此，可以通过改变入射光子的能量及电介质球面的介电常数对氢负离子在电介质球面附近的光剥离截面进行调控研究。研究结果对负离子体系在电介质球面附近的光剥离的实验研究可以提供一定的理论指导和参考价值。