球面波散射因子对光电子全息的影响

Spherical-wave corrections in photoelectron holography

用于研究物质结构的光电子全息 ,其物理机制是光电子波在固体中的散射。在电子能量为 5 0～ 2 0 0eV的中低能量下 ,不能用通常的平面波近似方法加以研究 ,必须考虑到光电子波的球面波本质。即使在电子能量大于 5 0 0eV的高能情况下 ,用平面波近似的方法也应对前向散射进行修正。本文以铜单晶薄膜为例 ,利用单重散射模型讨论了球面波近似模型下校正因子对光电子全息函数的影响 ,并与平面波近似作了比较。结果表明 ,对能量低于 2 0 0eV的光电子全息来说 ,球面波近似校正因子对前向散射和背向散射的振幅和相位都有较明显的修正。而在高能条件下 ,球面波近似校正因子主要影响光电子的前向散射 ,对背向散射的影响较小。进一步研究发现 ,球面波近似校正可以提高光电子全息的重现图的质量。

The scattering of photoelectron wave in the solid is a complex process.The plane wave approximation (PWA) is reasonably accurate for the study of photoelectron diffraction at high energies (over 500 eV).However,it is found that the PWA is not adequate even at moderate energies (50～200 eV),and so,it is necessary to take into account the spherical wave nature of the photoelectron final state.In this paper,a simple single scattering cluster model is developed to discuss the influence of spherical wave (SW) corrections on the photoelectron holography in comparison with the plane wave approximation.And we find that SW effects in forward scattering are much more important than that in backward scattering when the photoelectron energy is higher than 500 eV。In the photoelectron holography where the energy of photoelectron is lower than 200 eV SW corrections are obvious in both forward and backward scattering.