The UV Spectrum of the Lyman-Birge-Hopfield Band System of N2 Induced by Cascading from Electron Impact
The UV Spectrum of the Lyman-Birge-Hopfield Band System of N2 Induced by Cascading from Electron Impact
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电子碰撞级联引起的 N2 莱曼-伯奇-霍普菲尔德能带系统的紫外光谱
DOI：
10.1029/2019ja027546
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Joseph M. Ajello1, J. Scott
中科院分区：
文献类型：
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作者：
Joseph M. Ajello1, J. Scott
我们在实验室中测量了N2分子的莱曼-伯奇-霍普菲尔德（LBH）带系统（）在30-200 eV电子激发下的远紫外（FUV：125.0-170.0 nm）级联诱导光谱。级联跃迁开始于两个过程：辐射和碰撞诱导的电子跃迁（CIQs），涉及两个状态（和w1 Δu→a1 Δ g），随后是级联诱导跃迁 在这里使用的单散射压力下直接激发到a态会在电子束周围产生受限的LBH光谱辉光图案。我们已经空间解析了电子束与N2在径向距离为0-400 mm的三种气体压力下碰撞的电子感生辉光图案。这种成像测量是第一次在实验室中将单散射电子碰撞诱导荧光的光谱测量与两个LBH发射过程分离开来：直接激发，在电子束轴附近发射最强;级联诱导，在远离电子束轴的地方占主导地位。辐射级联和CIBs增强了a1基态v′ = 0-2振动能级的振动布居数，并在40、50、100和200 eV处提供了直接和级联诱导激发的LBH带系统的发射截面。
We have measured in the laboratory the far ultraviolet (FUV: 125.0–170.0 nm) cascade‐induced spectrum of the Lyman‐Birge‐Hopfield (LBH) band system ( ) of N2excited by 30–200 eV electrons. The cascading transition begins with two processes: radiative and collision‐induced electronic transitions (CIETs) involving two states ( andw1Δu→a1Πg), which are followed by a cascade induced transition at the single‐scattering pressures employed here. Direct excitation to thea‐state produces a confined LBH spectral glow pattern around an electron beam. We have spatially resolved the electron‐induced glow pattern from an electron beam colliding with N2at radial distances of 0–400 mm at three gas pressures. This imaging measurement is the first to isolate spectral measurements in the laboratory of single‐scattering electron‐impact‐induced fluorescence from two LBH emission processes: direct excitation, which is strongest in emission near the electron beam axis; and cascading‐induced, which is dominant far from the electron beam axis. The vibrational populations for vibrational levels from v′ = 0–2 of thea1Πgstate are enhanced by radiative cascade and CIETs, and the emission cross sections of the LBH band system for direct and cascading‐induced excitation are provided at 40, 50, 100, and 200 eV.