Measurement of Emission Cross Sections for Inert-gas Atoms by Electron Impact

在1991 ~ 2000年间，系统地测量了惰性气体原子的np→ns和ns→（n-1）p跃迁（Ne: n=3, Ar: n=4, Kr: n=5）从阈值到1000 eV的发射截面。我们确定了在可见光波长范围内的绝对发射截面以及到ns态的总级联截面。但是，在没有标准灯的情况下，需要进一步确认探测系统在近红外波长范围内的绝对光学灵敏度。我们采用了一种利用Ar光谱的所谓的brandling方法。所得的横截面部分显示出与先前报道的结果有相当大的差异。Paschen符号中的2p_9→1s_5跃迁特别有趣，因为2p_9状态是一个纯三重态，在ls方案中很好地用^ 3d_3表示。Ar和Kr的2p_9态的理论激发截面对冲击能E的依赖性几乎为~ E^<-3>，而实验得到的截面下降速度较慢。2p_9→1s_5跃迁的时间分辨强度衰减表明，2p_9态的大部分居群是由高能量下的里德伯态的级联跃迁引起的。

Emission cross sections for the np→ns and ns→(n-1)p transitions (Ne : n=3, Ar : n=4, Kr : n=5) of inert-gas atoms have been systematically measured from threshold to 1000 eV in the period of 1991〜2000. We have determined absolute emission cross sections as well as the total cascade cross sections to the ns-state in the visible wavelength range. However, a further reconfirmation had been desired for the absolute optical sensitivity in the near infrared wavelength range of the detection system where no standard lamp was available. We adopted a so-called brandling method utilizing Ar spectra. The obtained cross sections show considerable differences in part with those results previously reported.The 2p_9 → 1s_5 transition in Paschen notation is of particular interest because the 2p_9 state is a pure triplet state and well represented by the term^3 D_3 in the LS-scheme. Theoretical excitation cross sections for the 2p_9 state of Ar and Kr show almost 〜 E^<-3> dependence on the impact energy E, whereas, the experimentally obtained cross sections descend more slowly. Time-resolved intensity decays of the 2p_9 → 1s_5 transition show that the most of the population of the 2p_9 state is due to the cascade transitions from the higher lying Rydberg states at high energies.