Neutron-rich Environment Research Articles

Do we owe our existence to gravitational waves?

Two heavy elements essential to human biology are thought to have been produced by the astrophysical r-process, which occurs in neutron-rich environments: iodine is a constituent of thyroid hormones that affect many physiological processes including growth and development, body temperature and heart rate, and bromine is essential for tissue development and architecture. Collisions of neutron stars (kilonovae) have been identified as sources of r-process elements including tellurium, which is adjacent to iodine in the periodic table, and lanthanides. Neutron-star collisions arise from energy loss due to gravitational-wave emission from binary systems, leading us to suggest that gravitational waves have played a key role in enabling human life by producing iodine and bromine. We propose probing this proposal by searching in lunar material for live 129I deposited by a recent nearby kilonova explosion.

Fragmentation in Gravitationally Unstable Collapsar Disks and Subsolar Neutron Star Mergers

Although stable neutron stars (NSs) can in principle exist down to masses M ns ≈ 0.1 M ⊙, standard models of stellar core-collapse predict a robust lower limit M ns ≳ 1.2 M ⊙, roughly commensurate with the Chandrasekhar mass M Ch of the progenitor’s iron core (electron fraction Y e ≈ 0.5). However, this limit may be circumvented in sufficiently dense neutron-rich environments (Y e < 0.5) for which MCh∝Ye2 is reduced to ≲1 M ⊙. Such physical conditions could arise in the black hole accretion disks formed from the collapse of rapidly rotating stars (“collapsars”), as a result of gravitational instabilities and cooling-induced fragmentation, similar to models for planet formation in protostellar disks. We confirm that the conditions to form subsolar-mass NS (ssNS) may be marginally satisfied in the outer regions of massive neutrino-cooled collapsar disks. If the disk fragments into multiple ssNSs, their subsequent coalescence offers a channel for precipitating subsolar mass LIGO/Virgo gravitational-wave mergers that does not implicate primordial black holes. The model makes several additional predictions: (1) ∼Hz frequency Doppler modulation of the ssNS-merger gravitational-wave signals due to the binary’s orbital motion in the disk; (2) at least one additional gravitational-wave event (coincident within ≲hours), from the coalescence of the ssNS-merger remnant(s) with the central black hole; (3) an associated gamma-ray burst and supernova counterpart, the latter boosted in energy and enriched with r-process elements from the NS merger(s) embedded within the exploding stellar envelope (“kilonovae inside a supernova”).

On the “Loose” Constraint from IceCube Neutrino Nondetection of GRB 230307A

The recent extremely bright gamma-ray burst (GRB) from a binary neutron star merger, GRB 230307A, may offer a good probe for the production of GRB neutrinos. Within the constraint from IceCube neutrino nondetection, the limits for key physical parameters of this burst are extracted in different scenarios, including the fireball, Poynting-flux-dominated, and hybrid jet. Different from the former nearby “monsters” and due to its smaller isotropic equivalent radiated energy (E γ,iso ∼ 4 × 1052 erg), the constraint seems loose if nonthermal neutrinos produced from photomeson interactions are the only consideration. However, a quasi-thermal neutrino emission from hadronuclear processes is constrained in this neutron-rich postmerger environment, and the upper limit of the allowed nucleon loading factor is ∼a few. Based on this, a discussion is presented on the possible prompt emission mechanism and jet composition for GRB 230307A in the context of multimessenger astrophysics. It is worth noting that until now, no GRB neutrinos have been ever detected, even for the two brightest nearby GRBs ever observed (GRB 221009A and GRB 230307A), which have different dissipation mechanisms.

Estimation of the buildup of He-3 and Li-6 poisoning, He-4 and tritium activity in beryllium oxide reflector block in APSARA-U reactor

The Apsara-U research reactor, situated at the Bhabha Atomic Research Center, began its operation in 2018. This facility employs a fuel core configuration employing low-enriched uranium and reflector assemblies made of beryllium oxide. In neutron-rich environment of a nuclear reactor, these beryllium oxide reflector blocks participate in nuclear reactions identified as 9Be(n,α) and 9Be(n,2n). The 9Be(n,α) reaction initiates the formation of isotopes such as 4He, 6Li, 3He, and 3H in the process. The accumulation of gasses like 3He, 4He, and 3H causes the beryllium oxide reflector to swell, ultimately restricting how long it can effectively serve as a reflector or moderator material within the reactor. Extended periods of reactor shutdown result in a significant increase in the concentrations of 3He, mainly due to the radioactive decay of 3H. 6Li and 3He nuclei have significant neutron capture cross-sections, leading to a reduction in the reactor's reactivity, a phenomenon termed "poisoning". This effect varies depending on factors like neutron flux, neutron flux spectrum, and the reactor's operational history. Thorough investigations have been carried out to gain insights into the accumulation of 4He, 3He, 6Li, and 3H within beryllium oxide and their effects on reactivity considering the diverse levels of neutron exposure it encounters.

Finding r-II Sibling Stars in the Milky Way with the Greedy Optimistic Clustering Algorithm

R-process enhanced stars with [Eu/Fe] ≥ +0.7 (so-called r-II stars) are believed to have formed in an extremely neutron-rich environment in which a rare astrophysical event (e.g., a neutron-star merger) occurred. This scenario is supported by the existence of an ultra-faint dwarf galaxy, Reticulum II, where most of the stars are highly enhanced in r-process elements. In this scenario, some small fraction of dwarf galaxies around the Milky Way were r enhanced. When each r-enhanced dwarf galaxy accreted to the Milky Way, it deposited many r-II stars in the Galactic halo with similar orbital actions. To search for the remnants of the r-enhanced systems, we analyzed the distribution of the orbital actions of N = 161 r-II stars in the solar neighborhood by using Gaia EDR3 data. Since the observational uncertainty is not negligible, we applied a newly developed greedy optimistic clustering method to the orbital actions of our sample stars. We found six clusters of r-II stars that have similar orbits and chemistry, one of which is a new discovery. Given the apparent phase-mixed orbits of the member stars, we interpret that these clusters are good candidates for remnants of completely disrupted r-enhanced dwarf galaxies that merged with the ancient Milky Way.

Conceptual design of a GEM (gas electron multiplier) based gas Cherenkov detector for measurement of 17MeV gamma rays from T(D, γ)5He in magnetic confinement fusion plasmas.

The only method for assessing the fusion power throughput of a deuterium-tritium (DT) reactor presently relies on determining the absolute number of 14MeV neutrons produced in the DT plasma. An independent method, developed and investigated during the recent DT campaign at the Joint European Torus, is based on the absolute counting of 17MeV gamma rays produced by the competing T(D, γ)5He reaction that features a very weak branching ratio (about 3-6 × 10-6) when compared to the main T(D,n)4He reaction. The state-of-the-art spectrometer used for gamma-ray measurements in magnetic confinement fusion plasmas is LaBr3(Ce) scintillator detectors, although they require significant neutron shielding to extract a relatively weak gamma-ray signal from a much more abundant neutron field. A better approach relies on a gamma-ray detector that is intrinsically insensitive to neutrons. We have advanced the design of a gamma-ray counter based on the Cherenkov effect for gamma-rays whose energy exceeds 11MeV, optimized to work in the neutron-rich environment of a steady-state, magnetically confined fusion plasma device. The gamma-rays interact with an aluminum window and extract electrons that move into the radiator emitting photons via the Cherenkov effect. Since the Cherenkov light consists of few photons (25 on average) in the far UV band (100-200nm), a pre-amplifier is required to transport the photons to the neutron-shielded location, which may be a few meters away, where the readout elements of the detector, either a silicon or standard photomultiplier tube, are placed. The present work focuses on the development of a scintillating GEM (Gas Electron Multiplier) based pre-amplifier that acts as a Cherenkov photon pre-amplifier and wavelength shifter. This paper presents the result of a set of Garfield++ simulations developed to find the optimal GEM working parameters. A photon gain of 100 is obtained by biasing a single GEM foil to 1kV.

Correlations between nuclear landscape boundaries and neutron-rich r -process abundances

Motivated by the newly observed $^{39}\mathrm{Na}$ in experiments, systematic calculations of global nuclear binding energies with seven Skyrme forces are performed. We demonstrate the strong correlation between the two-neutron separation energies of $^{39}\mathrm{Na}$ and the total number of bound nuclei of the whole nuclear landscape. Furthermore, with calculated nuclear masses, we perform astrophysical rapid neutron capture process ($r$-process) simulations by using the nuclear reaction code talys and the nuclear reaction network code skynet. $r$-process abundances from ejecta of neutron star mergers (NSM) and core-collapse supernova are compared. Prominent covariance correlations between nuclear landscape boundaries and $r$-process abundances in the NSM scenario before the third peak are shown. We also see that statistical correlations disappear where shell effects dominated. This study highlights the need for further experimental studies of drip-line nuclei around $^{39}\mathrm{Na}$ for better constraints on nuclear landscape boundaries and the $r$-process in extremely neutron-rich environments.

Investigation of a Cherenkov-based gamma-ray diagnostic for measurement of 17 MeV gamma-rays from T(D, γ)5He in magnetic confinement fusion plasmas

At present, the only method for assessing the fusion power throughput of a reactor relies on the absolute measurement of 14 MeV neutrons produced in the D-T nuclear reaction. For ITER and DEMO, however, at least another independent measurement of the fusion power is required. The 5He* nucleus produced in the D-T fusion reaction has two de-excitation channels. The most likely is its disintegration in an alpha particle and a neutron, D + T → 5He* → α + n, by means of the nuclear force. There is however also an electromagnetic channel, with a branching ratio ∼10−5, which leads to the emission of a 17 MeV gamma-ray, i.e. D + T → 5He* → 5He + γ. The detection of this gamma-ray emission could serve as an independent method to determine the fusion power. In order to enable 17 MeV gamma-ray measurements, there is need for a detector with some coarse energy discrimination and, most importantly, capable of working in a neutron-rich environment. Conventional inorganic scintillators, such as LaBr3(Ce), have comparable efficiencies to neutrons and gamma-rays and they cannot be used for 17 MeV gamma-ray measurements without significant neutron shielding. In order to overcome this limitation, we here propose the conceptual design of a gamma-ray counter with a variable energy threshold based on the Cherenkov effect and designed to operate in intense neutron fields. The detector geometry has been optimized using Geant4 so to achieve a gamma-ray to neutron efficiency ratio better than 105. The design is based on a gas Cherenkov detector and the photo-sensor is still to investigated.

Atomic data calculations for Au i–Au iii and exploration in the application of collisional-radiative theory to laboratory and neutron star merger plasmas

ABSTRACT Neutron binary star mergers have long been proposed as sufficiently neutron rich environments that could support the synthesis of rapid neutron capture elements (r-process elements) such as gold. However, the literature reveals that beyond neutral and singly ionized systems, there is an incompleteness of atomic data for the remaining ion stages of importance for mergers. In this work, we report on relativistic atomic structure calculations for Au i–Au iii using the grasp0 codes. Comparisons to calculations using the Flexible Atomic Code suggest uncertainties on average of 9.2 per cent, 5.7 per cent, and 3.8 per cent for Au i–Au iii level energies. Agreement around ∼50 per cent is achieved between our computed A-values and those in the literature, where available. Using the grasp0 structure of Au i, we calculated electron-impact excitation rate coefficients and use a collisional-radiative model to explore the excitation dynamics and line ratio diagnostics possible in neutron star merger environments. We find that proper accounting of metastable populations is critical for extracting useful information from ultraviolet–visible line ratio diagnostics of Au i. As a test of our data, we applied our electron-impact data to study a gold hollow cathode spectrum in the literature and diagnosed the plasma conditions as Te = 3.1 ± 1.2 eV and $n_\textrm {e} = 2.7^{+1.3}_{-0.9}\times 10^{13}$ cm−3.

Characterization of a polyphenyl ether oil irradiated at high doses in a TRIGA Mark II nuclear reactor

Samples of a commercially available polyphenyl ether (PPE) oil are irradiated in the mixed neutron and gamma radiation field of the Pavia TRIGA Mark II reactor, at irradiation doses ranging from 0.78 MGy to 7.8 MGy. The oil is a nuclear grade product, whose radiation resistance reported in the product specification is based on cobalt-60 gamma irradiation data. The collection of additional data in a nuclear reactor radiation field performed in the present work, is motivated by the need to use this oil in neutron-rich environments such as targets and accelerators.The post-irradiation characterization of the oil samples here reported includes viscosity measurements, total acid number (TAN), Fourier transform infrared spectroscopy (FT-IR), gas chromatography (GC), gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) spectroscopy.The presented results evidence a remarkable increase of kinetic viscosity with the absorbed dose. Differences in the radiation-induced viscosity increase are observed comparing the data collected in mixed neutron and gamma radiation with the previous ones collected in cobalt-60 gamma radiation. This result emphasizes the need of further studies on the dependence of the radiation damage on different radiation environments. A negligible increase of TAN is reported. The FT-IR, GC, GPC and NMR show progressive polymerization with increasing dose. The increasing molecular size is in line with the viscosity data presented.

Atmospheric Neutron Monitoring through Optical Fiber-Based Sensing

The potential of fiber-based sensors to monitor the fluence of atmospheric neutrons is evaluated through accelerated tests at the TRIUMF Neutron Facility (TNF) (BC, Canada), offering a flux approximatively 109 higher than the reference spectrum observed under standard conditions in New York City, USA. The radiation-induced attenuation (RIA) at 1625 nm of a phosphorus-doped radiation sensitive optical fiber is shown to linearly increase with neutron fluence, allowing an in situ and easy monitoring of the neutron flux and fluence at this facility. Furthermore, our experiments show that the fiber response remains sensitive to the ionization processes, at least up to a fluence of 7.1 × 1011 n cm−², as its radiation sensitivity coefficient (~3.36 dB km−1 Gy−1) under neutron exposure remains very similar to the one measured under X-rays (~3.8 dB km−1 Gy−1) at the same wavelength. The presented results open the way to the development of a point-like or even a distributed dosimeter for natural or man-made neutron-rich environments. The feasibility to measure the dose caused by the neutron exposure during stratospheric balloon experiments, or during outer space missions, is presented as a case study of a potential future application.

Nuclear physics uncertainties in neutrino-driven, neutron-rich supernova ejecta

Neutrino-driven ejecta in core collapse supernovae (CCSNe) offer an interesting astrophysical scenario where lighter heavy elements between Sr and Ag can be synthesized. Previous studies emphasized the important role that ($\alpha,n$) reactions play in the production of these elements, particularly in neutron-rich and alpha-rich environments. In this paper, we have investigated the sensitivity of elemental abundances to specific ($\alpha,n$) reaction-rate uncertainties under different astrophysical conditions. Following a Monte Carlo nucleosynthesis study with over 36 representative astrophysical wind conditions, we have identified the most important reactions based on their impact on the final elemental abundances. Experimental studies of these reactions will reduce the nucleosynthesis uncertainties and make it possible to use observations to understand the origin of lighter heavy elements and the astrophysical conditions where they are formed.

Experimental Challenge to Heavy Element Synthesis under Explosive Burning on Neutron Stars

Binary stellar systems that involve a neutron star or two neutron stars make interesting phenomena, X-ray bursts and kilo-novae, respectively, which involve explosive burning either in the proton-rich environment or in the neutron-rich environment. These are very important problems for nuclear astrophysics. First, the current effort for the explosive hydrogen burning, the rapid proton capture (rp) process which would take place on a neutron star surface in X-ray burst is discussed together with a new X-ray observation that suggests the rp-process termination at around A = 100. The observation of the afterglow of the binary neutron star merger appears to be the kilo-nova predicted in the last decade in nuclear astrophysics, and to be the great success of the field. However, the detailed study of the kilo-nova by the r-process should be a great challenge for full understanding heavy element synthesis and the neutron star merger. Nuclear physics problems are discussed for the kilonova.

Influence of Density Dependence of Symmetry Energy in Hot and Dense Matter for Supernova Simulations

Abstract We study the influence of density-dependent symmetry energy at high densities in simulations of core-collapse supernovae, black hole formation, and proto–neutron star cooling by extending the relativistic mean field (RMF) theory used for the Shen equation-of-state (EOS) table. We adopt the extended RMF theory to examine the density dependence of the symmetry energy with a small value of the slope parameter L, while the original properties of the symmetric nuclear matter are unchanged. In order to assess matter effects at high densities, we perform numerical simulations of gravitational collapse of massive stars adopting the EOS table at high densities beyond 1014 g cm−3 with the small L value, which is in accord with the experimental and observational constraints, and compare them with the results obtained by using the Shen EOS. Numerical results for 11.2 and 15 M ⊙ stars exhibit minor effects around the core bounce and in the following evolution for 200 ms. Numerical results for 40 and 50 M ⊙ stars reveal a shorter duration toward the black hole formation with a smaller maximum mass for the small-L case. Numerical simulations of proto–neutron star cooling over 10 s through neutrino emissions demonstrate increasing effects of the symmetry energy at high densities. Neutrino cooling drastically proceeds in a relatively long timescale with high luminosities and average energies with the small symmetry energy. Evolution toward the cold neutron star is affected because of the different behavior of neutron-rich matter, while supernova dynamics around core bounce remains similar in less neutron-rich environments.

Origin of the non-carbonaceous–carbonaceous meteorite dichotomy

The isotopic composition of meteorites reveals a fundamental dichotomy between non-carbonaceous (NC) and carbonaceous (CC) meteorites. However, the origin of this dichotomy—whether it results from processes within the solar protoplanetary disk or is an inherited heterogeneity from the solar system's parental molecular cloud—is not known. To evaluate the origin of the NC–CC dichotomy, we report Ni isotopic data for a comprehensive set of iron meteorites, with a special focus on groups that have not been analyzed before and belong to the CC group. The new Ni isotopic data demonstrate that the NC–CC dichotomy extends to Ni isotopes, and that CC meteorites are characterized by a ubiquitous 58Ni excess over NC meteorites. These data combined with prior observations reveal that, in general, the CC reservoir is characterized by an excess in nuclides produced in neutron-rich stellar environments, such as 50Ti, 54Cr, 58Ni, and r-process Mo isotopes. Because the NC–CC dichotomy exists for refractory (Ti, Mo) and non-refractory (Ni, Cr) elements, and is only evident for nuclides produced in specific, neutron-rich stellar environments, it neither reflects thermal processing of presolar carriers in the disk, nor the heterogeneous distribution of isotopically anomalous Ca–Al-rich inclusions (CAI). Instead, the NC–CC dichotomy reflects the distinct isotopic composition of later infalling material from the solar system's parental molecular cloud, which affected the inner and outer regions of the disk differently. Simple models of the infall process by themselves can support either infall of increasingly NC-like material onto an initially CC-like disk, or infall of increasingly CC-like material in the absence of disk evolution by spreading. However, provided that CAIs formed close to the Sun, followed by rapid outward transport, their isotopic composition likely reflects that of the earliest infalling material, implying that the composition of the inner disk (i.e., the NC reservoir) is dominated by later infalling material, whereas the outer disk (i.e., the CC reservoir) preserved a compositional signature of the earliest disk. The isotopic difference between the inner and outer disk was likely maintained through the rapid formation of Jupiter, which prevented complete homogenization between material from inside (NC reservoir) and outside (CC reservoir) its orbit.

A-dependence of ΔΔ-bond and charge symmetry energies

The Δ -bond energies (ΔBΔΔ) of double-Δ hypernuclei provide a measure of the nature of the in-medium strength of the ΔΔ interaction. Likewise, the charge symmetry breaking in mirror nuclei with Δ and ΔΔ is expected to shed light on ΔN and ΔΔN interactions. A generalized mass formula, constructed earlier with broken SU(6) symmetry, is optimized and employed to calculate the separation energies from light to heavy nuclei. The new experimental data on ΔΔ-separation energy of a few double-Δ hypernuclei, and Δ-separation energy of several single-Δ hypernuclei have put more stringent constraint on this mass formula. The ΔBΔΔ values calculated with this optimized formula are in good agreement with the experimental data. This optimized mass formula can be used to predict ΔΔ-bond energy in neutron-rich environment, and to extract Coulomb-corrected symmetry energy from experimental data as well. It suggests existence of bound hypernuclei beyond the normal neutron-drip line.

RELATIVE CONTRIBUTIONS OF THE WEAK, MAIN, AND FISSION-RECYCLING r-PROCESS

ABSTRACT There has been a persistent conundrum in attempts to model the nucleosynthesis of heavy elements by rapid neutron capture (the r-process). Although the locations of the abundance peaks near nuclear mass numbers 130 and 195 identify an environment of rapid neutron capture near closed nuclear shells, the abundances of elements just above and below those peaks are often underproduced by more than an order of magnitude in model calculations. At the same time, there is a debate in the literature as to what degree the r-process elements are produced in supernovae or the mergers of binary neutron stars. In this paper we propose a novel solution to both problems. We demonstrate that the underproduction of nuclides above and below the r-process peaks in main or weak r-process models (like magnetohydrodynamic jets or neutrino-driven winds in core-collapse supernovae) can be supplemented via fission fragment distributions from the recycling of material in a neutron-rich environment such as that encountered in neutron star mergers (NSMs). In this paradigm, the abundance peaks themselves are well reproduced by a moderately neutron-rich, main r-process environment such as that encountered in the magnetohydrodynamical jets in supernovae supplemented with a high-entropy, weakly neutron-rich environment such as that encountered in the neutrino-driven-wind model to produce the lighter r-process isotopes. Moreover, we show that the relative contributions to the r-process abundances in both the solar system and metal-poor stars from the weak, main, and fission-recycling environments required by this proposal are consistent with estimates of the relative Galactic event rates of core-collapse supernovae for the weak and main r-process and NSMs for the fission-recycling r-process.

Astrophysical site(s) ofr-process elements in galactic chemodynamical evolution model

Astrophysical site(s) of rapid neutron-capture process ( r -process) is (are) not identified yet. Although core-collapse supernovae have been regarded as one of the possible candidates of the astrophysical site of r -process, nucleosynthesis studies suggest that serious difficulties in core-collapse supernovae to produce heavy elements with mass number of ≳110. Recent studies show that neutron star mergers (NSMs) can synthesize these elements due to their neutron rich environment. Some chemical evolution studies of the Milky Way halo, however, hardly reproduce the observed star-to-star scatters of the abundance ratios of r-process elements (e.g., Eu) in extremely metal-poor stars. This is because of their low rate (∼ 10 −4 yr −1 for a Milky Way size galaxy) and long merger time (≳ 100 Myr). This problem might be solved if the stars in the Galactic halo are consisted of the stars formed in dwarf galaxies where the star formation efficiencies were very low. In this study, we carry out numerical simulations of galactic chemo-dynamical evolution using an N-body/smoothed particle hydrodynamics code. We construct detailed chemo-dynamical evolution model for the Local Group dwarf spheroidal galaxies (dSphs) assuming that the NSMs are the major source of r -process elements. Our models successfully reproduce the observed dispersion in [Eu/Fe] as a function of [Fe/H] if we set merger time of NSMs, ≲ 300 Myr with the Galactic NSM rate of ∼ 10 −4 yr −1 . In addition, our results are consistent with the observed metallicity distribution of dSphs. In the early phase (≲1 Gyr) of galaxy evolution is constant due to low star formation efficiency of dSphs. This study supports the idea that NSMs are the major site of r -process nucleosynthesis.

Latest results of Skyrme-Hartree-Fock-Bogoliubov mass formulas

The latest developments made in deriving accurate mass predictions within the microscopic Skyrme Hartree-Fock-Bogolyubov (HFB) approach are described. Using the HFB method, we have refitted our BSk20 and BSk21 models, on which were based the HFB-20 and HFB-21 mass tables, to the 2353 measured masses of nuclei with N and Z ≥ 8 given in the newly available 2012 Atomic Mass Evaluation. In addition, we have now investigated the sensitivity to the symmetry coefficient J and the stiffness of the neutron matter equation of state. We present here in all 5 new Skyrme interactions, along with their corresponding mass tables. The root-mean square deviation obtained with our preferred model (HFB-24) with respect to essentially all the 2353 available mass data falls to 0.549 MeV, the best value ever found within the mean-field framework. Since our Skyrme force is also constrained by the properties of pure neutron matter this new model is particularly well-suited for application to astrophysical problems involving a neutron-rich environment, such as the elucidation of the r-process of nucleosynthesis, and the description of supernova cores and neutron-star crusts.

The Impact of Fission on R-Process Calculations

We have performed r-process calculations in neutron star mergers (NSM) and jets of magnetohydrodynamically driven (MHD) supernovae. In these very neutron-rich environments the fission model of heavy nuclei has an impact on the shape of the final abundance distribution and the second r-process peak in particular.We have studied the effect of different fission fragment mass distribution models in calculations of low-Ye ejecta, ranging from a simple parametrization to extensive statistical treatments (ABLA07).The r-process path ends when it reaches an area in the nuclear chart where fission dominates over further neutron captures. The position of this point is determined by the fission barriers and the neutron separation energies of the nuclei involved. As these values both depend on the choice of the nuclear mass model, so does the r-process path. Here we present calculations using the FRDM (Finite Range Droplet Model) and the ETFSI (Extended Thomas Fermi with Strutinsky Integral) mass model with the related TF and ETFSI fission barrier predictions. Utilizing sophisticated fission fragment distribution leads to a highly improved abundance distribution.