OH MASERS IN W33A

The circular polarization spectra in W33A are observed on emission from the ²Ⅱ_3/2 J=3/2, F=1→1 and F=2→2 transition of OH. The hydrogen density in the masing region is infered about 10⁷ cm^-3 in both the long thin tube and spherical maser,Apump rate of ～1(OH) cm^-3s^-1 is required in both geometries for the photon emission rate of ～10⁴⁶s^-1. The required pump efficiency is higher in the sphericalmaserthan in the thin tube.