Institute of Scientific Research, Boston College, Chestnut Hill, Massachusetts02159, United States.
Air Force Research Laboratory, Space Vehicles Directorate, Kirtland AFB, New Mexico87111, United States.
J Phys Chem A. 2023 Feb 16;127(6):1422-1435. doi: 10.1021/acs.jpca.2c07692. Epub 2023 Feb 5.
Chemiluminescence from a system of collisions, N/N/Kr/Kr/Xe/Xe + NH, at collision energies between 10 and 170 eV (center of mass, COM), was measured in the spectral range 300-1000 nm. The energy dependence of the emission excitation cross sections was quantified, and molecular signatures were fit to known spectroscopic constants to determine vibrational-state populations. For both N and N collision species, the strongest features were assigned to emissions from NH (A-X) and the atomic hydrogen Balmer series. For each of the spectra resulting from collisions with primary cations, the NH (A-X) emissions had the largest cross sections reaching values of (1.0-1.5) × 10 cm by 100 eV. Additional features originating from atomic nitrogen and NH (c-a) emissions were also observed. The NH (c-a) emissions accounted for about 8%, 13%, and 15% for total excited populations in collisions with Xe, N, and Kr, respectively. These transitions were consistent with short-range interactions resulting in collision-induced dissociation of the NH molecule with apparent energy thresholds between 20 and 30 eV and emission cross sections decreasing with ion mass. Evidence of charge exchange in the N + NH collisions was observed in the resulting spectra as broad transitions between 420 and 480 nm and were assigned to NH emitting from the (B) state. Differences between the spectra were observed as changes in the emission signal with the neutral collisions producing only 30% or 65% of the NH (A-X) emission cross sections compared to the cation results for xenon and krypton, respectively. For N and N, NH (A) was created in equal amounts at lower collision energies, but the emission for the neutral system increases above that of the cation at collision energies greater than 80 eV COM. In both cases, the threshold energy for appearance was below 10 eV, suggesting an additional pathway for NH (A) formation, namely, hydrogen abstraction or charge exchange and abstraction for the N and N, respectively. In all cases, the neutral NH (c-a) emission intensity was similar between neutral and cation pairs. The H-α emission line ( = 3-2) decreased to about 10%, 33%, and 50% of the corresponding cation spectra for xenon, krypton, and nitrogen, respectively.
在 10 至 170 电子伏特（质心，COM）的碰撞能下，测量了碰撞体系 N/N/Kr/Kr/Xe/Xe+NH 的化学发光，光谱范围为 300-1000nm。量化了发射激发截面的能量依赖性，并将分子特征拟合到已知的光谱常数，以确定振动态分布。对于 N 和 N 两种碰撞物种，最强的特征被分配给 NH（A-X）和原子氢巴尔默系列的发射。对于与初级阳离子碰撞产生的每个光谱，NH（A-X）发射的截面最大，在 100eV 时达到（1.0-1.5）×10 cm 的值。还观察到源自原子氮和 NH（c-a）发射的其他特征。NH（c-a）发射分别占 Xe、N 和 Kr 碰撞时总激发态的 8%、13%和 15%。这些跃迁与短程相互作用一致，导致 NH 分子的碰撞诱导解离，表观能阈值在 20 和 30eV 之间，发射截面随离子质量减小而减小。在 N+NH 碰撞的结果光谱中观察到电荷交换的证据，这是在 420 和 480nm 之间的宽跃迁，并被分配给 NH 从（B）态发射。中性碰撞产生的发射信号随光谱变化而观察到差异，仅产生与氙和氪的阳离子结果相比，NH（A-X）发射截面的 30%或 65%。对于 N 和 N，在较低的碰撞能下等量地产生 NH（A），但对于中性系统，在大于 80eV COM 的碰撞能下，NH（A）的发射增加超过阳离子。在两种情况下，出现的阈值能量都低于 10eV，这表明 NH（A）形成的另一种途径，即氢的提取或电荷交换和提取，分别针对 N 和 N。在所有情况下，中性和阳离子对之间的 NH（c-a）发射强度相似。H-α发射线（=3-2）分别减少到氙、氪和氮的相应阳离子光谱的 10%、33%和 50%左右。
