Electron Impact Excitation of Astrophysically Important Neutral Atoms
The cosmically abundant carbon, nitrogen, oxygen, and sulfur elements have their resonance transitions in the ultraviolet (UV) and far ultraviolet (FUV) wavelength domains of the spectrum. These atomic species are detected in a variety of astrophysical objects through emission lines. For example, several strong emission features of atomic oxygen and sulfur have been identified in spectra from Jupiter’s satellite Io and the Io torus and in stellar atmospheres in both ground and space based observations. The plasma diagnostic techniques based on spectroscopic line intensities, profiles and wavelengths are employed to understand and predict physical processes and conditions such as pressure, density, and chemical composition of the emitting plasma. The accuracy and completeness of data for a variety of atomic and molecular processes play a crucial role in these determinations. The non-Local Thermodynamic Equilibrium (NLTE) model calculations require not only complete data for radiative processes such as oscillator strengths and photoionization cross sections and rates, but also for collisional rates between the atomic species and electrons.
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