Measurement of dispersion at 6328 and 6401 Å due to the neon 1s5metastable atoms in a He-Ne discharge

Experimental measurements of the dispersive phase shift at 6328 and 6401 Å due to neon
1s_{5}
metastables in a He-Ne discharge are described. These measurements confirm the hypothesis of Arrathoon and Siegman that
1s_{5}
metastables are responsible for the observed current dependence of the oscillation frequency of a 6328-Å He-Ne laser.