Post-neutron mass chain yield distribution in the thermal neutron induced fission of $^{{{229}}}\text {Th}$

Abstract

The cumulative and independent yields of various fission products within the mass range of 77–151 have been measured in the $^{229}\hbox {Th}(\hbox {n}_{\mathrm {th}}$, f) reaction by using radiochemical methods together with an off-line $\upgamma$-ray spectrometric technique. The post-neutron mass chain yields were obtained from the cumulative fission yields by using charge distribution correction. From the mass yields data, the peak-to-valley (P/V) ratio, full width at tenth maximum (FWTM) of light and heavy mass wing, the average light mass (${{<}}\hbox {A}_{\mathrm {L}}{>}$) and heavy mass (${<}\hbox {A}_{\mathrm {H}}{>}$) as well as the average neutrons number (${<}\nu {>}$) were obtained. The fine structure of mass chain yield distribution (MD) in the $^{229}\hbox {Th}$($\hbox {n}_{\mathrm {th}}$, f) reaction was explained from the point of nuclear structure effect such as shell closure proximity and even-odd effect. The MD in the $^{229}\hbox {Th}$($\hbox {n}_{\mathrm {th}}$, f) reaction was compared with the MD of $^{\mathrm {235}}\hbox {U}$($\hbox {n}_{\mathrm {th}}$, f) reaction and the role of standard I and standard II asymmetric mode of fission was examined.