  In certain mass ranges, massive stars can undergo a violent pulsation
triggered by the electron/positron pair instability that ejects matter, but
does not totally disrupt the star. After one or more of these pulsations, such
stars are expected to undergo core-collapse to trigger a supernova explosion.
The mass range susceptible to this pulsational phenomena may be as low as 50-70
Msun if the progenitor is of very low metallicity and rotating sufficiently
rapidly to undergo nearly homogeneous evolution. The mass, dynamics, and
composition of the matter ejected in the pulsation are important aspects to
determine the subsequent observational characteristics of the explosion. We
examine the dynamics of a sample of stellar models and rotation rates and
discuss the implications for the first stars, for LBV-like phenomena, and for
superluminous supernovae. We find that the shells ejected by pulsational
pair-instability events with rapidly rotating progenitors (>30% the critical
value) are hydrogen-poor and helium and oxygen-rich.
