For a field of 15 T, I calculated the magnitude of the splitting, which was 1.391E-22 J (this is delta E), i.e. delta E = |e| / 2m hbar B_z (m2 - m1) where m2 and m1 are the m_l levels. In order to determine the spacings for the visible lines on the absorption spectra, will that just be relating the delta E value to lambda in the usual way? It seems a little strange here because the spacings would then be 1.4 mm (seems high). Anway.. I'd appreciate some insight.