Modeling of hydrogen ground state rotational and vibrational temperatures in kinetic plasmas

D. R. Farley, D. P. Stotler, D. P. Lundberg, S. A. Cohen

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

A dipole-quadrupole electron-impact excitation model, consistent with molecular symmetry rules, is presented to fit ro-vibronic spectra of the hydrogen Fulcher-α Q-branch line emissions for passively measuring the rotational temperature of hydrogen neutral molecules in kinetic plasmas with the coronal equilibrium approximation. A quasi-rotational temperature and quadrupole contribution factor are adjustable parameters in the model. Quadrupole excitation is possible due to a violation of the 1st Born approximation for low to medium energy electrons (up to several hundred eV). The Born-Oppenheimer and Franck-Condon approximations are implicitly shown to hold. A quadrupole contribution of 10% is shown to fit experimental data at several temperatures from different experiments with electron energies from several to 100. eV. A convenient chart is produced to graphically determine the vibrational temperature of the hydrogen molecules from diagonal band intensities, if the ground state distribution is Boltzmann. Hydrogen vibrational modes are long-lived, surviving up to thousands of wall collisions, consistent with multiple other molecular dynamics computational results. The importance of inter-molecular collisions during a plasma pulse is also discussed.

Original languageEnglish (US)
Pages (from-to)800-819
Number of pages20
JournalJournal of Quantitative Spectroscopy and Radiative Transfer
Volume112
Issue number5
DOIs
StatePublished - Mar 1 2011

All Science Journal Classification (ASJC) codes

  • Radiation
  • Atomic and Molecular Physics, and Optics
  • Spectroscopy

Keywords

  • Electron-impact excitation
  • Fulcher
  • Hydrogen
  • Rotational temperature

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