中文摘要：

利用新一代高性能（e,2e）电子动量谱仪,在400-2400 eV的大范围入射电子能量条件下,测量了乙烯分子电子密度的动量分布.实验测量的乙烯1b3g轨道电子动量分布与平面波冲量近似的理论计算结果相比,在低动量区和高动量区出现明显的上翘（turn up）效应,并且此上翘效应随着入射电子能量的增加而逐渐减小.进一步的分析证实由于分子的扭曲波效应引起1b3g轨道动量分布在低动量区和高动量区的上翘.实验测量结果将对分子扭曲波理论计算的建立提供实验依据.

英文摘要：

We report here the direct measurement of electron momentum distributions for ethylene using a newly developed high performance electron momentum spectrometer at different impact energies from 400 to 2400 eV. The ＂turn up＂ effects in the （e, 2e） cross sections of the lb3g orbital compared with the plane wave impulse approximation calculations are observed in both low and high momentum （p） regions, but such discrepancies become smaller with increase of the impact electron energies. It is suggested that the observed discrepancies are due to the distorted wave effects in molecules, which will provide experimental corroboration for theoretical calculations based on distorted waves in molecules.