超短超强激光与薄膜靶相互作用中不同价态碳离子的来源*

摘要

研究了超短超强激光与不同厚度薄膜Al靶相互作用中靶背法线方向碳离子的最初来源。通过对比分析碰撞电离率和场致电离率所起的作用，发现C4+及更低价态的碳离子主要由场致电离产生，而高价态的C5+和C6+离子主要来自于超热电子与靶表面的碰撞电离。%High charge state carbon ions are observed from the rear surface of thin foil irradiated by intense femtosecond laser pulse at intensities up to 6.4 × 1018 W/cm2. The origin of the ions is studied by analyzing the basic ionization process occurring at the rear surface. It is shown that the normally dominant ionization process is field ionization by barrier suppression for charge states less than He-like (C4+), while collisional ionization is significant for C5+and C6+.