Electron impact study of the 100 eV emission cross section and lifetime of the Lyman-Birge-Hopfield band system of N 2 : Direct excitation and cascade: Electron Impact Study of LBH Band System
Electron impact study of the 100 eV emission cross section and lifetime of the Lyman-Birge-Hopfield band system of N 2 : Direct excitation and cascade: Electron Impact Study of LBH Band System
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N 2 的 Lyman-Birge-Hopfield 能带系统的 100 eV 发射截面和寿命的电子撞击研究：直接激发和级联：LBH 能带系统的电子撞击研究
DOI：
10.1002/2017ja024087
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Johnson, P. V.
中科院分区：
文献类型：
--
作者：
Ajello, J. M.;Malone, C. P.;Holsclaw, G. M.;Hoskins, A. C.;Eastes, R. W.;McClintock, W. E.;Johnson, P. V.
利用电子碰撞诱导荧光方法测量了N2分子光学禁带莱曼-伯奇-霍普菲尔德（LBH）带系（a1 g→X1 +g）的100 eV发射截面.使用一个大的（1.5米直径）的真空室住房的电子枪系统和火星大气和挥发性EvolutioN使命成像紫外光谱仪光学工程模型，我们已经获得了校准的光谱测量的LBH波段系统从115到175 nm的视线范围内捕捉所有的光发射。这些测量代表了在实验室中直接分离单散射电子碰撞诱导荧光的第一个实验，该荧光来自a1基态的直接激发和对a1基态的级联贡献（a′1 − u和w1 Δu→a1 g→X1 +g）。总LBH发射横截面的测定是通过测量电子碰撞亚稳态发射的整个圆柱形辉光图案来完成的，通过成像视线测量从零到~400 mm径向距离的辉光强度，并计算LBH辉光图案的积分强度与同时观察到的具有良好建立的横截面的光学允许跃迁的积分强度的比值：Ni 120.0 nm。在100 eV时，a1电子态的“直接”发射截面被确定为σemdir=（6.41 ± 1.3）× 10− 18 cm 2。从辉光模式行为中观察到的一个重要结果是，由于邻近电子态之间的碰撞诱导级联跃迁，总（直接+级联）发射截面与压力有关。
We have measured the 100 eV emission cross section of the optically forbidden Lyman‐Birge‐Hopfield (LBH) band system (a1Πg→X1Σ+g) of N2by electron‐impact‐induced fluorescence. Using a large (1.5 m diameter) vacuum chamber housing an electron gun system and the Mars Atmosphere and Volatile EvolutioN mission Imaging Ultraviolet Spectrograph optical engineering model, we have obtained calibrated spectral measurements of the LBH band system from 115 to 175 nm over a range of lines of sight to capture all of the optical emissions. These measurements represent the first experiment to directly isolate in the laboratory single‐scattering electron‐impact‐induced fluorescence from both direct excitation of thea1Πgstate and cascading contributions to thea1Πgstate (a′1Σ−uandw1Δu→a1Πg→X1Σ+g). The determination of the total LBH emission cross section is accomplished by measuring the entire cylindrical glow pattern of the metastable emission from electron impact by imaging lines of sight that measure the glow intensity from zero to ~400 mm radial distance and calculating the ratio of the integrated intensity from the LBH glow pattern to that of a simultaneously observed optically allowed transition with a well‐established cross section: Ni120.0 nm. The “direct” emission cross section of thea1Πgstate at 100 eV was determined to beσemdir= (6.41 ± 1.3) × 10−18cm2. An important observation from the glow pattern behavior is that the total (direct + cascading) emission cross section is pressure dependent due to collision‐induced cascade transitions between close‐lying electronic states.