X Rays and Electrons Emitted in Coincidence with the Fission ofCf252

We have measured the emission times of $K$ x rays and the yield and spectra of conversion electrons produced in coincidence with the spontaneous fission of ${\mathrm{Cf}}^{252}$. The measurements of x-ray yield as a function of time since fission can be analyzed into components with half-lives of 2.4, 0.4, 0.05, and $M1-E2\mathrm{}$ mixtures with some $E2\mathrm{}$ and perhaps some $E1\mathrm{}$. The gross features of the yield as a function of mass can be understood in terms of the stable nuclear deformations beyond mass 150, of postulated deformations for the neutronrich nuclides near mass 108, and of the closed-shell properties of nuclides near mass 132. Various explanations for the sharp drop in yield beyond 153 are explored. It is suggested that the amount of spin acquired by a fragment at scission may depend critically on the partner fragment; spherical fragments are less effective at imparting spin to their partners than are deformed ones. This suggestion provides an explanation for the drop in electron yield at mass 153 and for some of the differences between the yield and spectrum of $K$ x rays for ${\mathrm{Cf}}^{252}$ and these quantities for ${\mathrm{U}}^{236}$.