The electron distribution function is calculated for a plasma created when a high-current, highenergy (-MeV) electron beam enters nitrogen gas. No spatial dependence is considered for the distribution function and the velocity is expanded in the two-term approximation. Time dependence is retained. Benchmark calculations are presented that compare code output with experimental results of electron deposition studies and swarm studies in nitrogen. Production efficiencies are given. The effect of inner-shell processes is discussed. An example illustrates the importance of the beam-induced electric field on the plasma generation and behavior. It shows that considerable ohmic energy deposition can be involved and that, consequently, production of certain species can be greatly enhanced.
Code 4700.1 Sa. NAME OF FUNDING/SPONSORING ORGANIZATION DARPA 8c. ADDRESS (C/ty, State, and ZIP Code) Arlington, VA 22209 8b. OFFICE SYMBOL-(If applicable) 11 TITLE (Include Security Clauification) ~ Electron Energy Deposition in Atomic Oxygen 5 MONITORING ORGANIZATION REPORT NUMBER(S) 7*. NAME OF MONITORING ORGANIZATION
The nature of the prepared state is crucial to an understanding of isolated-molecule intramolecular dynamics. A model is utilized to compare the created quantum superposition state in pulsed laser excitation from (1) a ground electronic state with regular nuclear wavefunctions to an excited electronic state with regular nuclear wavefunctions with that from (2) the regular ground state to an excited state with irregular nuclear wavefunctions. All results are in the quantum-mechanical small-molecule limit. Visual inspection of the created state and its evolution shows distinct qualitative differences in these two cases, although various theoretically studied quantities do not reveal an obvious distinction. The differences are expected to be experimentally observable in tirne-resolved emission.
A discrete, time-dependent energy deposition model is used to study high-energy electron-beam (100 eV–10 MeV) deposition in N and N+. Both time-dependent and steady-state secondary electron distributions are computed. The loss function, mean energies per electron-ion pair production (W), production efficiencies, and distribution functions are presented for a wide range of energies. The latest experimental and theoretical cross sections are used in the model which predicts that W is approximately 31 eV for N and 72 eV for N+ over a wide range of beam energies. The sensitivity of these results to assumed background ionization fractions is also investigated.
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