Fully resolved Zeeman pattern in the Stern-Gerlach deflection spectrum of O sub 2 (sup 3 SIGMA sub g sup (-), K = 1).

The Stern-Gerlach magnetic deflection spectra of a molecular beam of O sub 2 cooled by supersonic expansion to its lowest rotational level (K=1) reveals nine spatially separated peaks within a span of 2 cm. These peaks readily are assigned from a calculation of the Zeeman energies of the K=1 spin-rotation sublevels characterized by M sub J, and the assumption of a uniform field gradient within the deflecting magnet gap. However, the variable widths of the observed peaks and the decreasing deflection of certain M sub J peaks with increasing field above 14 kG requires the explicit consideration of field gradient inhomogeneities. The theory for this is developed and the spectral profiles again computed with field-gradient inhomogeneity and rotational temperature as variables. Agreement of the theoretical shifts, bandwidths and relative intensities with increasing field gradient when compared with the experimental spectra is very good, and T sub (rot) is found to be 3.5K.