Precision Measurements of Correlated Energies and Velocities of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">Cf</mml:mi></mml:mrow><mml:mprescripts/><mml:mrow/><mml:mrow><mml:mn>252</mml:mn></mml:mrow><mml:mrow/><mml:mrow/></mml:mmultiscripts></mml:mrow></mml:math>Fission Fragments

Correlated energies and velocities of single fission fragments from the spontaneous fission of $^{252}\mathrm{Cf}$ have been measured. Absolute energies and times of flight are obtained with estimated accuracies of \ifmmode\pm\else\textpm\fi{}0.5% from direct comparison measurements with 30- to 120-MeV $^{79}\mathrm{Br}$, $^{81}\mathrm{Br}$, and $^{127}\mathrm{I}$ ions from the tandem Van de Graaff accelerator. The post-neutron-emission kinetic parameters obtained from this experiment for $^{252}\mathrm{Cf}$ fragments are compared with pre-neutron-emission quantities obtained from double-time-of-flight experiments of Whetstone and of Milton and Fraser. Of special interest is the fine structure which appears in the post-neutron-emission mass distribution. It is shown that this structure reflects the fine structure observed in the pre-neutron-emission mass distribution, which in turn is known to reflect certain energetically preferred even-even fragment configurations in $^{252}\mathrm{Cf}$ spontaneous fission. Within the \ensuremath{\approx}2.5% mass resolution of the present experiment, no additional fine structure appears as a result of neutron boil-off to specific fragment masses. The number of neutrons $\ensuremath{\nu}(M)$ as a function of fragment mass has been calculated from the pre- and post-neutron-emission mass distributions. In an appendix, a "universal" energy calibration procedure for solid-state detectors for fission fragments is given; this procedure is based on the present absolute fragment energy determinations and takes into account the mass dependence of the pulse-height-versus-energy relation.

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