Mass and Nuclear Charge Distributions from the Spontaneous Fission of Fm254

The relative fission yields of 20 mass chains from $^{254}\mathrm{Fm}$ spontaneous fission were measured by direct high-resolution $\ensuremath{\gamma}$-ray spectroscopy of the gross fission products. Reflected yields were calculated based on a prompt-neutron fission yield of 3.94; the absolute yields were determined by requiring the sum of all yields to be 200%. A peak-to-valley ratio for the mass-yield curve of \ensuremath{\ge}18 was determined radiochemically by measuring the cumulative yields of $^{140}\mathrm{Ba}$ and $^{127}\mathrm{Sb}$.$^{254}\mathrm{Fm}$ was produced by irradiating $^{253}\mathrm{Es}$ in a high-flux reactor and then chemically separating the 3.24-h $^{254}\mathrm{Fm}$ from its 39.3-h $^{254}\mathrm{Es}^{m}$ parent. An aluminum "catcher" foil was used to collect the $^{254}\mathrm{Fm}$ fission products. Nuclear charge distribution studies included measurements of the independent yields of $^{140}\mathrm{La}$, $^{135}\mathrm{Xe}$, $^{134}\mathrm{I}$, and $^{132}\mathrm{I}$ relative to their cumulative yields from direct $\ensuremath{\gamma}$-ray-spectroscopy data.