Further studies of excitation-heating of ions

Abstract

Further studies have been made of long magnetically-confined vacuum carbon arcs in order to elucidate a previously proposed energy-pumping mechanism called `excitation-heating', explaining a drastic departure from thermodynamic equilibrium (T_i ~ 100 T_e). The ion densities of C²⁺ and the metastable C^2+* on which the mechanism depends, as well as of C³⁺, were measured by vacuum ultraviolet absorption spectroscopy, and the results support the concept of excitation-heating. Mass spectrometric studies of the arc periphery also showed C²⁺ and C³⁺ as the dominant ions. The Massey-Hasted adiabatic maximum criterion and the theory of Rydnik and Yavorskii are applied to the near-resonance intermediate reaction step C^2+* + C^2+* → C²⁺ + C²⁺ + 0.29 eV (→C²⁺ + C²⁺ + 13.0 eV) and predict the large reaction cross section at fairly low collisional energies needed by the excitation-heating process.