Abstract

The electronic assignment of a pure helium flashlamp continuum¹ (1500–8000 Å) proves to be an essential element in the characterization of plasma reactions. This enables approximation of laser gain and resolves the paradox of extremely strong flashlamp emission, which has been unobserved in e- beam devices. The high temperature formation of the ${\text{He}}_2^{+}\left(C^2{\text{Π}}_u\right)$ is discussed. Electron impact transitions are found to dominate radiative processes and enhance ion-molecule formation through Coulombic collisions. The excited dimer ions are formed extremely rapidly through two- body reactions with trimer ions. Numerous potential loss mechanisms are examined, the most significant being identified as ${\text{He}}_2^{+}\left(C^2{\text{Π}}_u\to B^2{\text{Σ}}_g^{+}\right)$ absorption commencing at wavelengths shorter than 3000 Å. A conservative estimate of spontaneous emission for a capillary discharge is deduced to estimate gain.

© 1992 Optical Society of America