  We present the results of an H-alpha monitoring campaign on the BeXRB and
microquasar system LS I +61 303. We use radial velocity measurements of HeI
lines in our spectra to re-evaluate the orbital elements and to better
establish the time of periastron. We list equivalent widths and other
parameters for the H-alpha emission line and discuss the orbital phase related
variations observed. We call attention to a dramatic episode of emission
weakening that occurred in less than a day that probably resulted from exposure
to a transient source of ionizing radiation. We argue that the increase in
H-alpha and X-ray emission following periastron probably results from the
creation of an extended density wave in the disk created by tidal forces. We
also discuss estimates of the size of the disk from the H-alpha equivalent
width measurements, and we suggest that the disk radius from the average
equivalent width corresponds to a resonant truncation radius of the disk while
the maximum equivalent width corresponds to a radius limited by the separation
of the stars at periastron. We note that a nearby faint companion is probably
an unrelated foreground object.
