It is reported that a hitherto unexplained optical transition in ZnTe is due to oxygen substituting isoelectronically for Te. A classification of isoelectronic traps into isoelectronic donors and acceptors is made. One striking difference between these two classes is apparent in the phonon sidebands of the $J=1\mathrm{}$ and $J=2\mathrm{}$ transitions occuring at each center.

• Received 29 June 1966

DOI:https://doi.org/10.1103/PhysRevLett.17.312