Dissociation of Molecular Nitrogen

该项目涉及开发原子和分子氮的基本数据，这些数据是更好地了解高层大气中的能量流动和化学所必需的。氮分子的电子冲击离解和光离解产生的氮原子要么处于基态N(4S)，要么处于激发态N（2D）或N（2P）。氮原子的反应性及其在奇氮循环中的作用敏感地取决于氮原子的激发状态。当离解产生的基态与激发态的比例从50:50到46:54变化时，预测热层NO浓度变化100%。虽然50:50的比例是在理论基础上假设的，但这个比例本身从未在实验中确定过。主要研究者开发了一种新技术，可以直接测量在N2解离中产生的两个氮原子的激发态。利用激光激发在氮分子的快光束中进行测量，研究了N2在10 ~ 18 eV范围内的激发态。该技术将用于精确测定N2激发态的预解离速率和形成的氮原子产物的激发状态。然后通过对N2的光解离和电子冲击解离所涉及的所有状态的求和，得到与N（4S）、N（2D）和N（2P）的分支比。

This project is concerned with developing basic data on atomic and molecular nitrogen that is needed to better understand energy flow and chemistry in the upper atmosphere. Electron impact dissociation and photodissociation of molecular nitrogen produce atomic nitrogen in either the ground state N(4S) or in one of its excited states, N(2D) or N(2P). The reactivity of atomic nitrogen and its role in the odd nitrogen cycle depends sensitively upon the state of excitation of the nitrogen atom. Changes by 100% in thermospheric NO concentrations are predicted when the ratio of ground to excited states produced in dissociation is varied from 50:50 to 46:54. While a ratio of 50:50 is assumed on theoretical grounds, the ratio itself has never been determined experimentally. The principle investigator has developed a novel technique that permits direct measurement of the excitation state of both nitrogen atoms produced in N2 dissociation. The measurement is carried out in a fast beam of nitrogen molecules using laser excitation to study excited states of N2 in the region from 10 to 18 eV. This technique will be used to determine precisely the rate of predissociation of excited states of N2 and the state of excitation of the atomic nitrogen products formed. Branching ratios to N(4S), N(2D), and N(2P) are then obtained by summation over all the states involved in photodissociation and electron impact dissociation of N2.