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A previous study of symmetric collisions of massive nuclei has shown that current models of multinucleon transfer (MNT) reactions do not adequately describe the transfer product yields. To gain further insight into this problem, we have measured the yields of MNT products in the interaction of 977 ($E/A=4.79$ MeV) and 1143 MeV ($E/A=5.60$ MeV) $^{204}\mathrm{Hg}$ with $^{208}\mathrm{Pb}$. We find that the yield of multinucleon transfer products are similar in these two reactions and are substantially lower than those observed in the reaction of 1257 MeV ($E/A=6.16$ MeV) $^{204}\mathrm{Hg}+^{198}\mathrm{Pt}$. We compare our measurements with the predictions of the GRAZING-F, dinuclear systems (DNS), and improved quantum molecular dynamics (ImQMD) models. For the observed isotopes of the elements Au, Hg, Tl, Pb, and Bi, the measured values of the MNT cross sections are orders of magnitude larger than the predicted values. Furthermore, the various models predict the formation of nuclides near the $N=126$ shell, which are not observed.

The Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) collaboration has performed measurements with a fission time projection chamber (fissionTPC) to study the fission process by reconstructing full three-dimensional tracks of fission fragments and other ionizing radiation. The amount of linear momentum imparted to the fissioning nucleus by the incident neutron can be inferred by measuring the opening angle between the fission fragments. Using this measured linear momentum, fission fragment angular distributions can be converted to the center-of-mass frame for anisotropy measurements. Angular anisotropy is an important experimental observable for understanding the quantum mechanical state of the fissioning nucleus and vital to determining detection efficiency for cross section measurements. Neutron linear momentum transfer to fissioning $^{235}$U, $^{238}$U, and $^{239}$Pu and fission fragment angular anisotropy of $^{235}$U and $^{238}$U as a function of neutron energies in the range 130 keV--250 MeV are presented.

The total kinetic energy (TKE) release in the fast neutron induced fission of 235U was measured for neutron energies E n = 2 – 100 MeV . The TKE distributions are Gaussian in shape. The mean post neutron emission TKE release decreases non-linearly with increasing neutron energy and can be represented as TKE(MeV) = 170.92 − 3.73774 log 10 ⁡ E n − 0.65028 ( log 10 ⁡ E n ) 2 . Abrupt changes in the variances of the TKE distributions are observed at the onset of 2nd, 3rd, etc. chance fission. For E n = 20 – 100 MeV , the variances are approximately constant. These observations are compared to the predictions of the GEF model for neutron-induced fission. This model describes many of the features of the TKE release adequately.

Symmetric collisions of massive nuclei, such as 238U + 248Cm, have been proposed as ways to make new n-rich heavy nuclei via multi-nucleon transfer (MNT) reactions. We have measured the yields of several projectile-like and target-like fragments from the reaction of 1360 MeV 204Hg + 198Pt. We find that current models for this symmetric collision (GRAZING, DNS, ImQMD) significantly underestimate the yields of these transfer products, even for small transfers. Keywords: Multi-nucleon transfer, GRAZING predictions, DNS model, Improved Quantum Molecular Dynamics model, 204Hg + 198Pt

Fission fragment angular distributions can provide an important constraint on fission theory, improving predictive fission codes, and are a prerequisite for a precise ratio cross section measurement. Available anisotropy data is sparse, especially at neutron energies above 5 MeV. For the first time, a three-dimensional tracking detector is employed to study fragment emission angles and provide a direct measurement of angular anisotropy. The Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) collaboration has deployed the fission time projection chamber (fissionTPC) to measure nuclear data with unprecedented precision. The fission fragment anisotropy of $^{235}$U has been measured over a wide range of incident neutron energies from 180 keV to 200 MeV; a careful study of the systematic uncertainties complement the data.

The normalized $^{238}$U(n,f)/$^{235}$U(n,f) cross section ratio has been measured using the NIFFTE fission Time Projection Chamber from the reaction threshold to $30$~MeV. The fissionTPC is a two-volume MICROMEGAS time projection chamber that allows for full three-dimensional reconstruction of fission-fragment ionization profiles from neutron-induced fission. The measurement was performed at the Los Alamos Neutron Science Center, where the neutron energy is determined from neutron time-of-flight. The $^{238}$U(n,f)/$^{235}$U(n,f) ratio reported here is the first cross section measurement made with the fissionTPC, and will provide new experimental data for evaluation of the $^{238}$U(n,f) cross section, an important standard used in neutron-flux measurements. Use of a development target in this work prevented the determination of an absolute normalization, to be addressed in future measurements. Instead, the measured cross section ratio has been normalized to ENDF/B-VIII.$\beta$5 at 14.5 MeV.

States in $^{209}\mathrm{Tl}$ were populated using a multinucleon transfer reaction with a $^{136}\mathrm{Xe}$ beam impinging on a thick $^{208}\mathrm{Pb}$ target at $E=785$ MeV. The beam was pulsed at 825-ns intervals in order to perform isomer decay spectroscopy. The known ${J}^{\ensuremath{\pi}}=17/{2}^{+}$ isomer in $^{209}\mathrm{Tl}$ was located at 1228(4) keV and measured to have a half-life of ${T}_{1/2}=146(10)$ ns. A second isomer with ${J}^{\ensuremath{\pi}}=13/{2}^{+}$ was found to have ${T}_{1/2}=14(5)$ ns. The previously suggested low-energy X and Y transitions were found to have energies 57(2) and 47(2) keV respectively, while the measurement of conversion coefficients and a new decay path make the spin assignments below the isomers experimentally firm. Correlating the delayed $\ensuremath{\gamma}$ transitions with the prompt beam flash allowed the decay of states above the isomer to be found. The longer-lived isomer represents full alignment of the simplest two-particle, one-hole configuration and illuminates the remarkably weak coupling of the proton hole to the $^{210}\mathrm{Pb}$ core.