THE RADIATIVE DECAY OF METASTABLE ARGON ATOMS IN A LOW-DENSITY ARGON PLASMA STREAM
Abstract
A low-density, luminous, supersonic, argon plasma stream about one meter in length produced by a conventional d-c arc plasma generator was s udied spectroscopically. The spectra consisted of neutral argon atom lines and second positive nitrogen bands. Stream enthalpy and velocity calculations rule out thermal excita ion and electron-ion recombina ion as sources of the radiation. Radiative decay of met stable argon atoms will, however, account for the long lifetimes of the radiating argon and also for the excitation of the nitrogen, which enters the stream by mixing with the ambient test cell gas. The existence of metastable atoms and their behavior re further examined by use of additive gases. Atoms with excitation levels below the potential of the argon metasta les (hydrogen and krypton) tend to quench the radiation, whereas those with higher excitation levels (helium and neon) have no effect on the argon metastables, and their presence is not spectroscopically detectable. The existence of metastable atoms and the fact that he stream luminosity is caused by their radiative decay plays an important role in diagnostic techniques and renders conventional spectroscopic and probe procedures of lit l us . he discovery of t e metastables within the gas s ream, however, provides a further aven e to studi s of collision processes. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1963
- Accession Number
- AD0294543
Entities
People
- L.e. Brewer
- W.k. Mcgregor
Organizations
- Arnold Engineering Development Complex