Molecular beam sampling of metastable atoms from a hollow cathode arc as a probe for the electron temperature

In a hollow cathode arc discharge in noble gases fast metastable atoms are produced by electron impact and heavy particle collisions. These metastables are sampled through an orifice in the end anode. In a time-of-flight machine the authors have measured the centre-line intensity and the velocity distribution of the beam of metastable atoms. Molecular beam sampling of ground state atoms gives accurate information on the ion velocity distribution and qualitative information on the ion and neutral density. The fractional intensity of the metastables relative to the intensity of the ground state atoms gives information on the electron temperature