Photon echoes in plasmas: collisional relaxation in helium on 2 ^3S_1–3 ^3P_012

Abstract

Photon echoes are observed for the first time in plasmas on atomic metastable states populated by rf discharge in helium at pressures from 0.01 to 0.5 Torr. The echoes are generated by tunable dye-laser excitation. The collision cross section for echo dephasing on the He 2 (3)S-3 (3)P transition at 3888 A by collisions with ground-state atoms is 5 x 10(-14) cm(2) +/- 20%. Echoes are also observed on the 3P metastable manifold in neon.