  We developed a method superposing two different fission modes calculated in a
four-dimensional Langevin model to obtain more accurate fission fragment yield
and total kinetic energy (TKE). The two fission modes correspond to the
standard I and standard II modes reported by Brosa et al., and parameters in
the Langevin model and the superposing ratio were determined to reproduce the
fission fragment yield of $^{240}$Pu of spontaneous fission. We also
investigated the fission fragment yields and the TKEs of other Pu isotopes by
using the same Langevin parameters and different superposing ratios, such as
spontaneous fission of $^{238,242}$Pu and neutron-induced fission of
$^{239}$Pu. The prompt fission observables, such as the neutron multiplicity,
the prompt fission neutron spectrum, and the independent fission product yield
were calculated in the Hauser-Feshbach statistical decay model implemented in a
nuclear reaction code TALYS with $^{239}$Pu(n,f) in the incident energies
ranging from thermal energy up to 5 MeV. The calculated fission observables
qualitatively reproduce several known trends while calculated results have
quantitative discrepancies between reported data. Although more improvements
are needed for the most important nuclides, it turned out that our approach has
the capability to provide prompt fission observables for difficult-to-measure
nuclides.
