Mo Reaction Research Articles

Measurement of effective 98Mo(n,γ)99 Mo reaction cross-section in the epi-cadmium neutron flux produced by 10 MeV electron LINAC with Ta-BeO assembly

An experiment was carried out to study the feasibility of 99Mo production using an electron accelerator based epi-cadmium neutron source. The neutrons were produced by the interaction of bremsstrahlung end-point energy of 10 MeV with BeO blocks and the neutrons thus produced were moderated using High Density Polyethylene blocks. Effective cross-section of 98Mo(n,γ)99Mo reaction was measured using foil activation method. An enhancement in the effective cross-section due to resonances in the epi-cadmium region was observed. The photons and neutron production/transport in the experimental set-up were simulated using the FLUKA Monte Carlo code. The simulations were found to be in good agreement with the experimental findings.

Tuning Local Atomic Structures in MoS2 Based Catalysts for Electrochemical Nitrate Reduction.

In recent years, there has been a substantial surge in the investigation of transition-metal dichalcogenides such as MoS2 as a promising electrochemical catalyst. Inspired by denitrification enzymes such as nitrate reductase and nitrite reductase, the electrochemical nitrate reduction catalyzed by MoS2 with varying local atomic structures is reported. It is demonstrated that the hydrothermally synthesized MoS2 containing sulfur vacancies behaves as promising catalysts for electrochemical denitrification. With copper doping at less than 9% atomic ratio, the selectivity of denitrification to dinitrogen in the products can be effectively improved. X-ray absorption characterizations suggest that two sulfur vacancies are associated with one copper dopant in the MoS2 skeleton. DFT calculation confirms that copper dopants replace three adjacent Mo atoms to form a trigonal defect-enriched region, introducing an exposed Mo reaction center that coordinates with Cu atom to increase N2 selectivity. Apart from the higher activity and selectivity, the Cu-doped MoS2 also demonstrates remarkably improved tolerance toward oxygen poisoning at high oxygen concentration. Finally, Cu-doped MoS2 based catalysts exhibit very low specific energy consumption during the electrochemical denitrification process, paving the way for potential scale-up operations.

Exploring the role of softness on the fusion dynamics of 58,64Ni+92,100Mo reactions

The structure of target and projectile nuclei can significantly affect the reaction dynamics at low energies. In the present work, the fusion mechanism of 58,64Ni+92,100Mo reactions involving the Mo isotopes exhibiting peculiar soft nature is explored within the relativistic mean-field (RMF) formalism. The cross-section for the considered reactions is obtained using the ℓ-summed Wong model furnished with nuclear interaction potential calculated within the self-consistent RMF formalism. The calculations are done for the two sets of RMF parameters, namely, NL3∗ and NL1, which give different values for various characteristics of nuclear matter at the saturation. A lower fusion barrier and consequently, a higher cross-section is obtained for the parameter set with comparatively softer equation of state (EoS). On comparing the theoretical cross-section with the available experimental data, an underestimation of fusion cross-section with respect to the experimental data at the sub-barrier energies is noted for the NL3∗ parametrizations. The match improves for the NL1 set having soft EoS with slight underestimation of data noted for all the considered reactions. These observations infer that the incomprehensible softness of Mo-isotopes also persists in their fusion dynamics, and the nuclear potential obtained within the RMF formalism is observed to underestimate the fusion probability for the reactions involving Mo-isotopes. The compressible nature of Mo-isotopes is inferred to enhance the fusion cross-section, and nuclear potential obtained for parameter set with soft EoS is observed to be more suitable for the description of their fusion dynamics.

KANTBP 3.1: A program for computing energy levels, reflection and transmission matrices, and corresponding wave functions in the coupled-channel and adiabatic approaches

A FORTRAN program for calculating energy values, reflection and transmission matrices, and corresponding wave functions in a coupled-channel approximation of the adiabatic approach is presented. In this approach, a multidimensional Schrödinger equation is reduced to a system of the coupled second-order ordinary differential equations on a finite interval with the homogeneous boundary conditions of the third type at left- and right-boundary points for the discrete spectrum and scattering problems. The resulting system of such equations, containing potential matrix elements and first-derivative coupling terms is solved using high-order accuracy approximations of the finite element method. The scattering problem is solved with non-diagonal potential matrix elements in the left and/or right asymptotic regions and different left and right threshold values. Benchmark calculations for the fusion cross sections of 36S+48Ca, 64Ni+100Mo reactions are presented. As a test desk, the program is applied to the calculation of the reflection and transmission matrices and corresponding wave functions of the exact solvable wave-guide model, and also the fusion cross sections and mean angular momenta of the 16O+144Sm reaction. Program summaryProgram Title: KANTBPCPC Library link to program files:https://doi.org/10.17632/4vm9fhyvh3.1Licensing provisions: CC BY NC 3.0Programming language: FORTRANNature of problem: In the adiabatic approach [1], a multidimensional Schrödinger equation for quantum reflection [2], the photoionization and recombination of a hydrogen atom in a homogeneous magnetic field [3–6], the three-dimensional tunneling of a diatomic molecule incident upon a potential barrier [7], wave-guide models [8], the fusion model of the collision of heavy ions [9–11], and low-energy fusion reactions of light- and medium mass nuclei [12] is reduced by separating the longitudinal coordinate, labeled as z, from transversal variables to a system of second-order ordinary differential equations containing the potential matrix elements and first-derivative coupling terms. The purpose of this paper is to present a program based on the use of high-order accuracy approximations of the finite element method (FEM) for calculating energy levels, reflection and transmission matrices and wave functions for such systems of coupled-channel second order differential equations (CCSODEs) on finite intervals of the variable z∈[zmin,zmax] with homogeneous boundary conditions of the third-type at the left- and right-boundary points, which follow from the discrete spectrum and scattering problems.Solution method: The boundary-value problems for the system of CCSODEs are solved by the FEM using high-order accuracy approximations [13,14]. The generalized algebraic eigenvalue problem AF=EBF with respect to pair unknowns (E,F), arising after the replacement of the differential eigenvalue problem by the finite-element approximation, is solved by the subspace iteration method [14]. The generalized algebraic eigenvalue problem of a special form (A−EB)F=DF with respect to pair unknowns (D,F) arising after the corresponding replacement of the scattering boundary problem in open channels at fixed energy value, E, is solved by the L DLT factorization of the symmetric matrix and back-substitution methods [14].Additional comments including restrictions and unusual features: The user must supply subroutine POTCAL for evaluating potential matrix elements. The user should also supply subroutines ASYMEV (when solving the eigenvalue problem) or ASYMSL and ASYMSR (when solving the scattering problem) which evaluate asymptotics of the wave functions at boundary points in the case of a boundary conditions of the third-type for the above problems.

Solving the Puzzles of the Decay of the Heaviest Known Proton-Emitting Nucleus ^{185}Bi.

Two long-standing puzzles in the decay of ^{185}Bi, the heaviest known proton-emitting nucleus are revisited. These are the nonobservation of the 9/2^{-} state, which is the ground state of all heavier odd-A Bi isotopes, and the hindered nature of proton and α decays of its presumed 60-μs 1/2^{+} ground state. The ^{185}Bi nucleus has now been studied with the ^{95}Mo(^{93}Nb,3n) reaction in complementary experiments using the Fragment Mass Analyzer and Argonne Gas-Filled Analyzer at Argonne National Laboratory's ATLAS facility. The experiments have established the existence of two states in ^{185}Bi; the short-lived T_{1/2}=2.8_{-1.0}^{+2.3} μs, proton- and α-decaying ground state, and a 58(2)-μs γ-decaying isomer, the half-life of which was previously attributed to the ground state. The reassignment of the ground-state lifetime results in a proton-decay spectroscopic factor close to unity and represents the only known example of a ground-state proton decay to a daughter nucleus (^{184}Pb) with a major shell closure. The data also demonstrate that the ordering of low- and high-spin states in ^{185}Bi is reversed relative to the heavier odd-A Bi isotopes, with the intruder-based 1/2^{+} configuration becoming the ground, similar to the lightest At nuclides.

Catalytic and photocatalytic activity of Urtica dioica-mediated Ud-ZnO nanoparticles

Due to their pollution-free process, low-cost, and high-quality products, plant-mediated synthesis routes have been increasingly integrated and extended for preparing a different kind of nanomaterials particularly metals/metal oxides nanoparticles (NPs). In this work, Urtica dioica (U. dioica) ethanolic leaf extract mediated ZnO NPs (Ud-ZnO NPs) were synthesized and applied for photodegradation of methyl orange (MO, C14H14N3NaO3S) and rhodamine B (RhB, C28H31ClN2O3) dyes under ultraviolet (UV) light irradiation. Also, the catalytic activity of the prepared Ud-ZnO NPs was examined for catalytic reduction of toxic 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The chemical structure, surface morphology, crystalline structure, elemental composition, and light properties of the prepared Ud-ZnO NPs investigated using Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX) and UV–visible diffuse reflectance spectroscopy (DRS) analyses, respectively. The SEM analysis illustrated the hexagonal phase structure with no significant agglomerations. The particle size of synthesized Ud-ZnO NPs was ranging between 26.5 and 73.7 nm with a mean particle size of 44.9 nm. The optical band gap (Eg) of the synthesized Ud-ZnO NPs estimated via DRS spectroscopy using Tauc plot was found to be 3.14 eV. The quantitative photocatalytic activity of prepared Ud-ZnO NPs indicated that 73.4 % of MO and 85 % of RhB were degraded photochemically within 90 and 140 min, respectively, indicating high photocatalytic activity. The kinetics of the photodegradation MO and RhB reactions, and also, rapid catalytic reduction 4NP reaction was analyzed based on the Langmuir-Hinshelwood (L-H) model, indicating a pseudo-first-order reaction with the reaction rate constants of 0.0155 min−1, 0.0121 min−1, and 0.0158 s−1, respectively. The results verified the effectiveness of the U. dioica leaf extract as an active reducing and capping agent for preparing Ud-ZnO NPs.

The reaction of amorphous iron sulfide with Mo(VI) under different pH conditions

Iron sulfide (FeS) is an important scavenger for hexavalent molybdate (Mo(VI)) in an anoxic environment; it plays a crucial role in the mobilization and transformation of Mo(VI), although the underlying reaction mechanisms between Mo(VI) and FeS remain unclear. This study investigates the Mo(VI) reaction kinetics with the amorphous FeS over a pH range 5.0–9.0 and Mo’s chemical form on the FeS surface. It is found that the Mo(VI) reaction kinetics with FeS follow a pseudo first-order model, and the reaction rate constant (kobs) increases with a decrease in the pH value. The kobs at pH 5.0 is 0.027 min−1, which is about 38 times higher than that at pH 9.0. The rapid Mo(VI) removal under acidic conditions is due to quick Mo(VI) transformation into stable MoS2 and thiomolybdate (MoVOxSy). The amount of MoS2 formed on the surface of FeS increases with a decrease in the pH value. Under neutral and alkaline conditions, Mo(VI) is not transformed into MoS2 by FeS because the precipitation of iron oxy-hydroxide passivates the active sites of FeS. The study also investigates the effect of the initial dosage of FeS (20–200 mg L−1) and Mo(VI) (10–50 mg L−1) on the reaction kinetics of Mo(VI) with FeS. The results provides important information on the environmental fate of Mo(VI) in the anoxic environment containing amorphous FeS.

Synthesis, Lithium Insertion and Thermal Stability of Si–Mo Alloys

Li insertion was investigated in SixMo100−x (90 ≥ x ≥ 70, Δx = 10) alloys prepared by mechanical ball milling. X-ray diffraction (XRD) and quantitative phase analysis were used to analyze phase compositions of these Si–Mo alloys, and how these phase compositions changed with milling times. The results of quantitative phase analysis showed that cr-Si converted into a-Si within 1 h during milling, and the Si–Mo reactions were nearly complete after only 4-h milling. During electrochemical cycling, the Si–Mo samples with high initial Mo contents and long milling times displayed good crystalline Li15Si4 suppression and stable cycling performance. In addition, thermal stability of some selected Si–Mo alloys was studied. The Si80Mo20 16 h alloy combines good thermal stability and a high volumetric capacity of about 1300–1400 Ah L−1 after heat treatment at 600 °C or 800 °C, which may allow the alloy to be further improved by carbon coating at high temperature.

Tumor microenvironment-triggered MoS2@GA-Fe nanoreactor: A self-rolling enhanced chemodynamic therapy and hydrogen sulfide treatment for hepatocellular carcinoma

We report the preparation of gallic acid (GA)-modified MoS2 nanosheets (MoS2@GA) with high Fe(III) loading. The MoS2@GA-Fe can function as a “Fenton Nanoreactor” in the tumor microenvironment (TME), in which GA-Fe(III) can be reduced to GA-Fe(II) by glutathione (GSH) and amounts of reactive hydroxyl radicals (•OH) are generated during the Fenton reaction. Notably, the MoS2 degrades into small fragments during the process, and more Mo(IV) reaction sites are exposed on the surface, resulting in a “snowball effect” and enhanced •OH production. Furthermore, unsaturated S atoms can capture protons in the TME and form hydrogen sulfide (H2S). We combined the photoacoustic imaging and magnetic resonance imaging contrast properties of MoS2@GA-Fe and constructed an imaging-guided chemodynamic treatment, featuring excellent antitumor efficiency and biosafety. The TME-responsive “Fenton Nanoreactor” provides a promising strategy with enhanced translational potency for tumor therapy.

Production cross-sections of Mo-isotopes induced by fast neutrons based on the 9Be(p, n) reaction

We measured the flux-weighted average cross-sections of the 100Mo(n, 2n)99Mo and 92Mo(n, 3n)90Mo reactions with the average neutron energies between 14.0- and 31.8-MeV by using an activation and off-line γ-ray spectrometric technique. The fast neutrons were generated based on the 9Be(p, n) reaction with the proton energies of 25-, 35- and 45-MeV from the MC-50 Cyclotron at the Korea Institute of Radiological and Medical Sciences (KIRAMS). The neutron flux was measured by using the 27Al(n, α)24Na monitor reaction, whereas the neutron spectra were simulated by using the MCNPX 2.6.0 code. The theoretical cross-sections of the 100Mo(n, 2n)99Mo and 92Mo(n, xn)91.90,89Mo reactions as a function of mono-energetic neutron were calculated by using the TALYS-1.9 code. The present results for the 100Mo(n, 2n)99Mo and 92Mo(n, 3n)90Mo reactions are compared with the calculated neutron flux-weighted average values based on the literature data and theoretical cross-sections as a function of mono-energetic neutron energy, and show a good agreement.

Compressional-mode resonances in the molybdenum isotopes: Emergence of softness in open-shell nuclei near A = 90

“Why are the tin isotopes soft?” has remained, for the past decade, an open problem in nuclear structure physics: models which reproduce the isoscalar giant monopole resonance (ISGMR) in the “doubly-closed shell” nuclei, 90Zr and 208Pb, overestimate the ISGMR energies of the open-shell tin and cadmium nuclei, by as much as 1 MeV. In an effort to shed some light onto this problem, we present results of detailed studies of the ISGMR in the molybdenum nuclei, with the goal of elucidating where–and how–the softness manifests itself between 90Zr and the cadmium and tin isotopes. The experiment was conducted using the 94,96,98,100Mo(α,α′) reaction at Eα=386 MeV. A comparison of the results with relativistic, self-consistent Random-Phase Approximation calculations indicates that the ISGMR response begins to show softness in the molybdenum isotopes beginning with A=92.

Measurement of 100Mo (n, 2n) 99Mo reaction cross section and covariance analysis using extended unscented transformation technique at the incident neutron energy of 13.9 MeV

In this paper, the measurement and covariance analysis of the cross section of 100 Mo (n, 2n) 99 Mo reaction, with the 197 Au (n, 2n) 196 Au reaction being used as the monitor, at the incident neutron energy of 13.9 MeV is reported. The 3 H (d, n) 4 He nuclear reaction is used as the neutron source. The experiment was performed at the Purnima neutron facility, BARC. The method of activation with off-line -ray spectrometry is used. The covariance analysis of the 100 Mo (n, 2n) 99 Mo reaction is also performed, for the first time, using the extended unscented transformation (EUT) technique 1 , which is an extension of unscented transformation (UT) technique 2 , for the determination of partial uncertainties arising due to attributes in combination with the micro-correlation technique of Geraldo and Smith 3 . The present results obtained for 100 Mo (n, 2n) 99 Mo reaction cross section are found to be in good agreement with EXFOR data and the theoretically calculated value using the TALYS 1. 8 code. Comparisons with the data in the available basic evaluated nuclear data libraries, such as ENDF/B-VIII.0, JEFF-3.3, JENDL-4.0, ROSFOND-2010, CENDL-3.1 and TENDL 2017 are also presented and discussed.

THE LARGE ANGLE QUASI-ELASTIC SCATTERING CROSS SECTIONS AND THE EFFECTIVE WEIGHT FUNCTION BASED ON THE BARRIER DISTRIBUTION FOR 32S+92,94,96,98,100Mo REACTIONS

We studied quasi-elastic scattering and the effective weight function for the barrier distribution for 32S+92,94,96,98,100Mo reactions have been calculated simultaneously in a wide range of bombarding energies around the Coulomb barrier. The quasi-elastic angular distribution data are analyzed using the optical model code with Woods-Saxon potentials. It is shown that the calculations taken into account, for these reactions can explain structures of the quasi-elastic cross-section and the quasi-elastic barrier distribution. These results indicate that the coupled-channels formalism can still valid even for the various mass systems. The large-angle quasi-elastic scattering reactions were scrutinized with the identical core-core potential recommended for designating fusion reactions. Given the effect of a barrier distribution and nucleon transfer on the Woods-Saxon potential, the calculated semi-elastic scattering cross-sections of a series of reactions are in good harmony each other.

99 Mo recoil atoms yield in the 100 Mo(p,x) reaction on cyclotron irradiation of Mo nanofilms.

We study the possibility of increasing the specific activity of 99 Mo produced by irradiating molybdenum targets with the use of the Szilard-Chalmers effect. According to the Szilard-Chalmers effect, recoil atoms of the 99 Mo radionuclide can be produced in nuclear reactions and retained in surrounding buffer substance. The objective of our work is to measure the yield of recoil atoms in the buffer as a function of the molybdenum layer thickness. The yield of recoil 99 Mo atoms in the 100 Mo(p,x)99 Mo nuclear reaction as a function of metallic molybdenum nanolayer thickness has been measured. Measurements were carried out after irradiation of nanolayers in the U-150 cyclotron with 28-MeV protons. Nanolayers of molybdenum with thickness of 30 to 220 nm were produced by magnetron sputtering on sapphire plates. The yield of the mass of 99 Mo recoil atoms was found to be the highest with the molybdenum layer thickness of 80 ± 5 nm. The enrichment factor (EF) has been defined as a ratio of the 99 Mo collector specific activity (SA) to the entire target SA before separation as EF = 1200 ± 150. The specific activity of 99 Mo produced in the collector was estimated to be approximately equal to 25 Ci·g-1 .

Influence of enriched 100Mo on Mo reaction yields

In accelerator-driven 99Mo/99mTc production, the 100Mo enrichment level should be chosen carefully as it greatly affects the yields of the involved Mo reactions. To facilitate selecting the 100Mo enrichment level, we defined a figure of merit called density change coefficient and developed its calculation program. Density change coefficients calculated for nine commercial enriched 100Mo products are presented and their use in selecting the 100Mo enrichment level is discussed.

Towards Neutron Capture on Exotic Nuclei: Demonstrating (d,pγ) as a Surrogate Reaction for (n,γ).

The neutron-capture reaction plays a critical role in the synthesis of the elements in stars and is important for societal applications including nuclear power generation and stockpile-stewardship science. However, it is difficult-if not impossible-to directly measure neutron capture cross sections for the exotic, short-lived nuclei that participate in these processes. In this Letter we demonstrate a new technique which can be used to indirectly determine neutron-capture cross sections for exotic systems. This technique makes use of the (d,p) transfer reaction, which has long been used as a tool to study the structure of nuclei. Recent advances in reaction theory, together with data collected using this reaction, enable the determination of neutron-capture cross sections for short-lived nuclei. A benchmark study of the ^{95}Mo(d,p) reaction is presented, which illustrates the approach and provides guidance for future applications of the method with short-lived isotopes produced at rare isotope accelerators.

Accelerator-Based Methods in Radio-Material 99Mo/99mTc Production Alternatives by Monte Carlo Method: The Scientific-Expedient Considerations in Nuclear Medicine

Some accelerator technologies are already used for commercial [Formula: see text]Mo-99mTc production, as the economic criteria are considered representative of the main differences between diverse technologies including accelerators and reactors. This study has provided a review of known and potential [Formula: see text]Mo production using conventional medical facilities. Accelerator-based method in 99mTc production via ([Formula: see text], [Formula: see text]) direct reaction on [Formula: see text]Mo was simulated using 18[Formula: see text]MeV proton beam. Meanwhile, a conceptual design for indirect [Formula: see text]Mo production via [Formula: see text]Mo([Formula: see text])[Formula: see text]Mo and [Formula: see text]Mo(n,[Formula: see text]2n)[Formula: see text]Mo reactions was investigated when an electron source of 35[Formula: see text]MeV by accelerator is used. These indirect reactions were explored via inserted [Formula: see text]Mo samples at different positions inside the lead region. Furthermore, Adiabatic Resonance Crossing (ARC) method based on proton accelerator via transmutation in [Formula: see text]Mo([Formula: see text]Mo was examined when the 30[Formula: see text]MeV proton beam is used. Saturation activity and yield were investigated using alternative proposed methods. The potential proliferation risk associated with accelerator technetium production is minimal. While accelerators could be turned into neutron sources which could in turn be used to irradiate [Formula: see text]U to breed plutonium, and centrifuges used to enrich [Formula: see text]Mo for targets could conceivably be turned to enriching uranium, this would result in very tiny global production capability particularly compared with research or power reactors. The potential of the fresh methods could provide a replacement or complement over current reactor-based supply sources in various radioisotopes production purposes.

Evaporation channel as a tool to study fission dynamics

The dynamics of the fission process is expected to affect the evaporation residue cross section because of the fission hindrance due to the nuclear viscosity. Systems of intermediate fissility constitute a suitable environment for testing such hypothesis since they are characterized by evaporation residue cross sections comparable or larger than the fission ones. Observables related to emitted charged particles, due to their relatively high emission probability, can be used to put stringent constraints on models describing the excited nucleus decay and to recognize the effects of fission dynamics. In this work model simulations are compared with the experimental data collected via the S32+100Mo reaction at Elab=200 MeV. Consequently we pointed out, exploring an extended set of evaporation channel observables, the limits of the statistical model and the large improvement obtained with a dynamical model. Moreover we stress the importance of using an apparatus covering a large fraction of 4π to extract observables. Finally, we discuss the opportunity to measure more sensitive observables by a new detection device in operation at LNL.

De-excitation of the strongly coupled band in Au177 and implications for core intruder configurations in the light Hg isotopes

Excited states in the proton-unbound nuclide $^{177}$Au were populated in the $^92}$Mo($^{88}$Sr, p2n) reaction and identified using the Jurogam-II and GREAT spectrometers in conjunction with the RITU gas-filled separator at the University of Jyvaskyla Accelerator Laboratory. A strongly coupled band and its decay path to the 11/2−α-decaying isomer have been identified using recoil-decay tagging. Comparisons with cranked Hartree-Fock-Bogoliubov (HFB) calculations based on Skyrme energy functionals suggest that the band has a prolate deformation and is based upon coupling the odd 1h11/2 proton hole to the excited 02+ configuration in the $^{178}$Hg core. Although these configurations might be expected to follow the parabolic trend of core Hg(02+) states as a function of neutron number, the electromagnetic decay paths from the strongly coupled band in $^{177}$Au are markedly different from those observed in the heavier isotopes above the midshell. This indicates that a significant change in the structure of the underlying A+1Hg core occurs below the neutron midshell.

Informing neutron capture nucleosynthesis on short-lived nuclei with (d,p) reactions

Neutron capture on unstable nuclei is important in understanding abundances in r-process nucleosynthesis. Previously, the non-elastic breakup of the deuteron in the (d,p) reaction has been shown to provide a neutron that can be captured by the nucleus and the gamma-ray decay of the subsequent compound nucleus can be modelled to predict the gamma-ray decay of the compound nucleus in the (n,γ) reaction. Preliminary results from the 95 Mo(d,pγ) reaction in normal kinematics support the (d,pγ) reaction as a valid surrogate for neutron capture. The techniques to measure the (d,pγ) reaction in inverse kinematics have been developed.