  We develop a theoretical treatment of polarization spectroscopy and use it to
make predictions about the general form of polarization spectra in the alkali
atoms. Using our model, we generate theoretical spectra for the D2 transitions
in 87Rb, 85Rb, and 133Cs. Experiments demonstrate that the model accurately
reproduces spectra of transitions from the upper hyperfine level of the ground
state only. Among these, the closed transition F -> F' = F + 1 dominates, with
a steep gradient through line center ideally suited for use as a reference in
laser locking.
