the spectra show a dip at a certain excitation energy. without the dip it says that certain directions are preferred over others, or thus that the magnetic moments are alligned. At the dip this anisotropy is reduced, more different energy levels are populated. So you can conclude that at this excitation frequency, other states get populated. Or thus that this is a resonance frequency. The two states are a few MHz away from eachother, which can be explained with hyperfine splitting of energy levels.