Prompt emission calculations for ${}^{252}$Cf(SF) focused on post-neutron fragment distributions and different correlations between pre- and post-neutron fragment quantities

The present investigation answers to the international request of updating fission yields data for applications, by revisiting the calculations for ${}^{252}$Cf(SF) performed by the deterministic prompt emission model code DSE (Deterministic Sequential Emission) with focus on different distributions of post-neutron fragments, different correlations between pre- and post-neutron fragment quantities and distributions related to pre-neutron fragments in correlation with the sequential prompt neutron emission. The influence of both the energy partition in fission and the pre-neutron fragment distribution Y(A,TKE) on different distributions of post-neutron fragments (independent FPY, isotonic yield Y(N${}_p$) and kinetic energy distributions of post-neutron fragments KE${}_p$(Z), KE${}_p$(A${}_p$)) and on different correlations between pre- and post-neutron fragment quantities is investigated by using: a) two methods of TXE partition, one based on the modeling at scission implemented in the DSE model code and another based on a parameterization of the temperature ratio of complementary fully accelerated fragments R${}_T$(A${}_H$) and b) three reliable experimental Y(A,TKE) data. The DSE results of independent FPY (Y(Z,A${}_p$), Y(A${}_p$)) are obtained in good agreement with the existing experimental data of ${}^{252}$Cf(SF). Both the energy partition in fission and the Y(A,TKE) distribution influence the Y(A${}_p$) structure. Again the most pronounced peaks in the Y(A${}_p$) structure are due to even-Z fragments while the odd Z fragments contribute to pronounced dips. But the role of the even-odd effect is less important than in the previous studied case of ${}^{235}$U(n${}_{th}$,f) because the global even-odd effect in Y(Z) is almost 10 times lower in the case of ${}^{252}$Cf(SF) compared to ${}^{235}$U(n${}_{th}$,f). The correlation between the excitation energy of pre-neutron fragments E* and KE${}_p$, consisting of a well delineated sawtooth shape (looking as a reflection in mirror of the well known sawtooth shape of $\nu$(A)) is maintained in the case of ${}^{252}$Cf(SF), too. The large number of (A,Z,TKE) configurations taken into account in the DSE treatment allows the investigation of neutron excesses of pre- and post-neutron fragments. This reveals an interesting behaviour consisting of oscillations with a periodicity of about 5 mass units of both neutron excesses of pre- and post-neutron fragments as a function of A (in the asymmetric fission region). The oscillation amplitudes of neutron excesses are significantly higher and clearly visible in the case of ${}^{235}$U(n${}_{th}$,f) compared to ${}^{252}$Cf(SF) for which they are less visible. This behaviour is a consequence of the charge polarization $\Delta$Z(A) and rms(A) of the isobaric charge distribution (entering the deterministic construction of the fragmentation range of DSE model) which always exhibit oscillations with a periodicity of about 5 mass units, due to the periodicity of nuclear properties. The magnitude of the global even-odd effect in fragment charge is reflected in the magnitude of oscillation amplitudes in $\Delta$Z(A) and rms(A) and, as consequence, in the magnitude of oscillation amplitudes of neutron excesses of pre- and post-neutron fragments. The almost linear decrease of neutron excess of post-neutron fragments as a function of TKE as well as the behaviour of excitation energy distributions of pre-neutron fragments leading to each number "n" of emission sequences are explained, too.