Artículos (Física Atómica, Molecular y Nuclear)

URI permanente para esta colecciónhttps://hdl.handle.net/11441/10864

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The n_TOF facility at CERN
(EDP Sciences, 2024-06-07) Tagliente, G.; Aberle, O.; Alcayne, V.; Amaducci, S.; Andrzejewski, J.; Babiano Suárez, V.; Cortés Giraldo, Miguel Antonio; Guerrero Sánchez, Carlos; Lerendegui Marco, Jorge; Pérez Maroto, Pablo; Pavón Rodríguez, J. A.; Quesada Molina, José Manuel; Žugec, P.; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear
The neutron Time-of-Flight (TOF) research facility at CERN, n_TOF, has been a pioneering platform for neutron cross-section measurements since its inception in 2001. It boasts three distinct experimental areas, each tailored to address a specific range of neutron energies. This paper delves into the intricacies of the n_TOF facility, including its recent upgrade during the Long Shutdown 2 (LS2) at CERN. Additionally, it highlights the key characteristics of the detectors employed for capture and fission cross-section measurements, paving the way for future research endeavors.
The multichannel experimental and theoretical study of the 12C(18O,18F)12B single charge exchange reaction mechanism
(EDP Sciences, 2024-03-14) Spatafora, Alessandro; Carbone, Diana; Cappuzzello, Francesco; Cavallaro, Manuela; Acosta, Luis E.; Agodi, Clementina; Lay Valera, José Antonio; Zagatto, Vinicius A. B.; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; European Union
The study of a network of nuclear reactions populated in the 18O + 12C collision is the main topic of the present paper. It was performed to test nuclear structure and reaction theories in describing the full reaction mechanism occurring in the (18O, 18F) single charge exchange nuclear reaction. From the experimental side, an 18O beam was produced at 275 MeV incident energy by the K800 superconducting cyclotron and the MAGNEX magnetic spectrometer was used at the Laboratori Nazionali del Sud of the Istituto Nazionale di Fisica Nucleare to momentum analyse the ejectiles produced in the nuclear reactions within the same experimental setup. From the theoretical side, the proposed approach consists of analysing the whole network of nuclear reactions in the framework of a unique comprehensive and coherent theoretical calculation. This holistic approach, applied both to the experimental and theoretical analysis, is the main feature and novelty of the work presented here.
Searching for particle-hole cluster bands in 8Be using the ISOLDE Solenoidal Spectrometer
(EDP Sciences, 2024-10-28) Haverson, Kristian C. Z.; Smith, Robin; Gai, Moshe; Hughes, Owen; Tindle, Olivia; Bishop, Jack; Gómez Ramos, Mario; Casal Berbel, Jesús; Al-Aqeel, Muneerah A.M.; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; UK Science and Technology Facilities Council (STFC); European Union (UE)
The 7Be(d, p)8Be∗ reaction was measured in inverse kinematics at a beam energy of 11 MeV/u using the ISOLDE Solenoidal Spectrometer, in order to identify and characterise high-excitation states in 8Be. The spin-parities of many of the states in the 16−20 MeV region can be explained as being particle-hole excitations within a two-centre shell model. The present experiment aims to elucidate the spin parities of higher excited states, > 20 MeV, to assess their candidacy as rotational excitations of the aforementioned particlehole states. The beam intensity in this experiment was measured using a downstream Micron S1 double-sided silicon strip detector to pick up elastically scattered deuterons. The focus of this paper is to present methods for calculating the beam intensity, which is key for extracting the spectroscopic factors of the measured states. Preliminary excitation spectra are also presented.
An overloaded pure silica zeolite ISV synthesized using a phosphonium cation
(Royal Soc Chemistry, 2025-01-20) Yu, HJ; Rodríguez Gómez, Salvador; Gao, ZR; Camblor, MA; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Ministerio de Ciencia e Innovación (MICIN). España; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; Agencia Estatal de Investigación. España; European Union (UE)
A pure silica zeolite with ISV structure was synthesized using the tricyclopentylmethylphosphonium (Cp3MP+) cation under fluoride media. Analysis of the organic content in the zeolite suggested the presence of more than four cations per unit cell, while fluoride anions were exclusively located in the four double four-membered rings of the structure. 29Si solid-state NMR demonstrated a significant concentration of Q3 Si species, i.e., S̲i̲(OSi)3(OH), in the structure, which afforded charge balance but contrasted with the most common observation of defect-free pure silica zeolites prepared in fluoride media at nearneutral pH. Calculations showed that improved stability was obtained in an overloaded (i.e., containing more Cp3MP+ than F− and three-channel crossings) defective zeolite. The calculated stabilization of ISV was larger with Cp3MP+ than with the cyclohexyl analog used to produce ZEO-1, a zeolite with an extralarge 3D pore system. Substitution of small amounts of Cp3MP+ by tetraethylammonium stopped crystallization instead of producing ISV/BEC intergrowths, despite calculations on the bare zeolites suggesting improved stability of the intergrowths. This rendered the observed difficulty in obtaining such intergrowths puzzling and likely dependent on a disruption of the host–guest assembly. Compared with prior ISV materials, this zeolite displayed a minimum amount of disorder, which, however, was sufficient to impede proper Rietveld refinement.
A semi-analytical perspective on massive red galaxies
(EDP Scienses SA, 2025-01-20) Stoppacher, Doris; Montero Dorta, A. D.; Artale, MC; Knebe, A.; Padilla, Nicolás; Benson, A. J.; Behrens, C.; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear
Context. The evolution of galaxies within a self-consistent cosmological context remains one of the most outstanding and challenging topics in modern galaxy formation theory. Investigating the assembly history and various formation scenarios of the most massive and passive galaxies, particularly those found in the densest clusters, will enhance understanding of why galaxies exhibit such a remarkable diversity in structure and morphology. Aims. In this paper, we simultaneously investigate the assembly history and redshift evolution of semi-analytically modelled galaxy properties of luminous and massive central galaxies between 0.56 < z < 4.15 alongside their connection to their halos as a function of large-scale environment. Methods. We extracted sub-samples of galaxies from a mock catalogue representative of the well-known BOSS-CMASS sample, which includes the most massive and passively evolving system known today. Utilising typical galaxy properties such as star formation rate, (g-i) colour, and cold gas-phase metallicity (Zcold), we tracked the redshift evolution of these properties across the main progenitor trees. Results. We present results on galaxy and halo properties, including their growth and clustering functions, for each of our sub-samples. Our findings indicate that galaxies in the highest stellar and halo mass regimes are the least metal enriched (using Zcold as a proxy) and consistently exhibit significantly larger black hole masses and higher clustering amplitudes compared to sub-samples selected by such properties as colour or star formation rate. This population forms later and retains large reservoirs of cold gas. In contrast, galaxies in the intermediate and lower stellar or halo mass regimes consume their cold gas at a higher redshift and were among the earliest and quickest to assemble their stellar and black hole masses. In addition, we observed a clear trend where the clustering of the galaxies selected according to their Zcold-values (either low-Zcold or high-Zcold) depends on the density of their location within the large-scale environment. Conclusions. We assume that the galaxies in the low-Zcold and high-Zcold sub-samples form and evolve through distinct evolutionary channels that are predetermined by their location within the large-scale environment of the cosmic web. Furthermore, their clustering dependence on the environment could be an important area for further investigation.
Multi-view fast-ion D-alpha Spectroscopy Diagnostic at ASDEX Upgrade
(American Institute of Physics, 2013) Geiger, B.; Dux, R.; McDermott, R. M.; Potzel, S.; Reich, M.; Ryter, F.; Weiland, M.; Wünderlich, D.; García Muñoz, Manuel; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear
A novel fast-ion D-alpha (FIDA) diagnostic that is based on charge exchange spectroscopy has been installed at ASDEX Upgrade. The diagnostic uses a newly developed high-photon-throughput spectrometer together with a low-noise EM-CCD camera that allow measurements with 2 ms exposure time. Absolute intensities are obtained by calibrating the system with an integrating sphere and the wavelength dependence is determined to high accuracy using a neon lamp. Additional pertur-bative contributions to the spectra, such as D2-molecular lines, the Stark broadened edge D-alpha emission, and passive FIDA radiation have been identified and can be subtracted or avoided experimentally. The FIDA radiation from fast deuterium ions after charge exchange reactions can therefore be analyzed continuously without superimposed line emissions at large Doppler shifts. Radial information on the fast ions is obtained from radially distributed lines of sight. The investigation of the fast-ion velocity distribution is possible due to three different viewing geometries. The independent viewing geometries access distinct parts of the fast-ion velocity space and make tomographic reconstructions possible.
JET Diagnostic Enhancements in Preparation for DT Operations
(American Institute of Physics, 2016) Figueiredo, J.; Murari, A.; Pérez Von Thun, C.; Marocco, D.; Tardocchi, M.; Belli, F.; García Muñoz, Manuel; Silva, A.; Soare, S.; Craciunescu, T.; Hawkes, N.; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; European Union (UE)
In order to complete the exploitation of the JET ITER-like Wall and to take full benefit from deuterium-tritium experiments on JET, a set of diagnostic system refurbishments or upgrades is in progress. These diagnostic enhancements focus mainly on neutron, gamma, fast ions, instabilities, and operations support. These efforts intend to provide better spatial, temporal, and energy resolution while increasing measurement coverage. Also previously non-existing capabilities, such as Doppler reflectometry is now available for scientific exploitation. Guaranteeing diagnostic reliability and consistency during the expected DT conditions is also a critical objective of the work and systems being implemented. An overview of status and scope of the ongoing projects is presented.
JET Diagnostic Enhancements Testing and Commissioning in Preparation for DT Scientific Campaigns
(American Institute of Physics, 2018) Figueiredo, J.; Murari, A.; Pérez Von Thun, C.; Marocco, D.; Tardocchi, M.; Belli, F.; García Muñoz, Manuel; Silva, A.; Craciunescu, T.; Blanchard, P.; Zychor, I.; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; European Union (UE)
In order to optimize the scientific exploitation of JET (Joint European Torus) during the upcoming deuterium-tritium experiments, a set of diagnostic systems is being enhanced. These upgrades focus mainly on the experimental and operational conditions expected during tritium campaigns. It should be stressed that measurements relevant for burning plasmas are specifically targeted. Previously non-available capabilities, such as a current measurement system fully covering all poloidal field circuits, are described in detail. Instrument descriptions, performance prediction, testing, and initial commissioning results of these systems are presented.
Validation of the Synthetic Model for the Imaging Heavy ion Beam Probe at the ASDEX Upgrade Tokamak (invited)
(AIP Publishing, 2024) Oyola Domínguez, Pablo; Birkenmeier, G.; Lindl, H.; Galdón Quiroga, Joaquín; Rueda Rueda, José; Viezzer, Eleonora; Rodríguez González, A.; Hidalgo Salaverri, Javier; García Muñoz, Manuel; Tal, B.; Anda, G.; Kalis, J.; Lunt, T.; Refy, D.; Videla Trevin, M.; ASDEX Upgrade Team; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Universidad de Sevilla. Departamento de Ingeniería Mecánica y Fabricación; Ministerio de Ciencia e Innovación (MICIN). España; Helmholtz Association. Alemania; European Union (UE). H2020; European Union (UE)
Recent experiments at the ASDEX Upgrade tokamak have provided the first ever measurements from the imaging heavy-ion beam probe. In this work, we show that the developed simulation framework can reproduce qualitatively the measurement's observed shape and position. Quantitatively, we demonstrate that the model reproduces, within the experimental uncertainties, the observed signal levels. A detailed explanation of the synthetic model is presented, along with the calibration of the optical setup that reproduces the measurements.
Bacterial chemotaxis considering memory effects
(American Physical Society, 2025-05-15) Mayo León, Manuel; Soto, Rodrigo; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT). Chile; ANID Millennium Science Initiative. Chile; Ministerio de Ciencia e Innovación (MICIN). España
hemotaxis in bacteria such as Escherichia coli is controlled by the slow methylation of chemoreceptors. As a consequence, intrinsic time and length scales of tens of seconds and hundreds of micrometers emerge, making the Keller-Segel equations invalid when the chemical signal changes on these scales, as occurs in several natural environments. Using a kinetic approach, we show that chemotaxis is described using the concentration field of the protein that controls tumbling in addition to bacterial density. The macroscopic equations for these fields are derived, which describe the nonlocal response.
Bacterial chemotaxis considering memory effects: Derivation of the reaction-diffusion equations
(American Physical Society, 2025-05-15) Mayo León, Manuel; Soto, Rodrigo; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT). Chile; Ministerio de Ciencia e Innovación (MICIN). España; ANID Millennium Science Initiative. Chile
Bacterial chemotaxis for the case of Escherichia coli is controlled by methylation of chemoreceptors, which in a biochemical pathway regulates the concentration of the CheY-P protein that finally controls the tumbling rate. As a consequence, the tumbling rate adjusts to changes in the concentration of relevant chemicals, such as to produce a biased random walk toward chemoattractants or against the repellers. Methylation is a slow process, implying that the internal concentration of CheY-P is not instantaneously adapted to the environment, and therefore the tumbling rate presents a memory. This implies that the Keller–Segel equations used to describe chemotaxis at the macroscopic scale, which assume a local relation between the bacterial flux and the chemical gradient, cannot be fully valid as memory and the associated nonlocal response are not taken into account. To derive the new equations that replace the Keller–Segel ones, we use a kinetic approach, in which a kinetic equation for the bacterial transport is written considering the dynamics of the protein concentration. When memory is large, the protein concentration field must be considered a relevant variable on equal foot as the bacterial density. Working out in detail the Chapman–Enskog method, the dynamical equations for these fields are obtained, which have the form of reaction-diffusion equations with flux and source terms depending on the gradients on the chemical signal. Also, the transport coefficients are obtained entirely in terms o the microscopic dynamics, showing important symmetry properties and giving their values of the case of E. coli. Solving the equations for an inhomogeneous signal it is shown that the response is nonlocal, with a smoothing length as large as 170µ⁢m for E. coli. The homogeneous response and the relaxational dynamics are also studied in detail. For completeness, the case of small memory is also studied, in which case the Chapman–Enskog method reproduces the Keller–Segel equations, with explicit expressions for the transport coefficients.
Interplay of nuclear structure and dynamics with light exotic beams: the study of the reactions 8B+64Zn and 9Li-4He
(EDP Sciences, 2024-10-18) Di Pietro, Alessia; Spartá, Roberta; Fernández García, Juan Pablo; Figuera, Pierpaolo; Cognata, Marco La; Moro Muñoz, Antonio Matías; Shotter, Alan C.; Torresi, Domenico; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; European Union (UE)
This paper reports on investigations of elastic scattering reactions involving both, one proton-rich and one neutron-rich radioactive nuclei, 8B and 9Li respectively. These investigations highlighted the effects that the peculiar nuclear structure of these nuclei has on the reaction dynamics.
Heavy-ion induced double charge exchange reaction in a multi-channel approach: the research program of the NUMEN project
(EDP Sciences, 2024-10-08) Cappuzzello, Francesco; Lenske, Horst; Cavallaro, Manuela; Agodi, Clementina; Auerbach, Naftali; Bijker, Roelof; Lay Valera, José Antonio; Spatafora, Alessandro; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; European Union (UE)
We give an updated view of the status and prospects of heavy-ion double charge exchange (HI-DCE) reaction studies performed at the Laboratori Nazionali del Sud of the Istituto Nazionale di Fisica Nucleare (INFN-LNS) in the context of the NUMEN project. The important role of HI-DCE for nuclear reaction, nuclear structure and double beta-decay investigations is outlined. A powerful way to scrutinize the nuclear response to HI-DCE is to consistently link it to the information extracted from the competing direct reactions pointing to a multi-channel description of the whole network of quasi-elastic processes. Indeed, these complementary studies are mandatory in order to minimize the systematic errors in the data analyses and build a many-facets and parameter-free representation of the systems under study.
Formal theory of heavy ion double charge exchange reactions
(EDP Sciences, 2024-05-14) Lenske, Horst; Bellone, Jessica; Colonna, Maria; Gambacurta, Danilo; Lay Valera, José Antonio; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Deutsche Forschungsgemeinschaft / German Research Foundation (DFG); Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España
The theory of heavy ion double charge exchange (DCE) reactions A(Z, N) → A(Z ± 2, N ∓ 2) is recapitulated emphasizing the role of Double Single Charge Exchange (DSCE) and pion-nucleon Majorana DCE (MDCE) reactions. DSCE reactions are of second–order distorted wave character, mediated by isovector nucleon-nucleon (NN) interactions. The DSCE response functions resemble the nuclear matrix elements (NME) of 2ν2β decay. The MDCE process proceeds by a dynamically generated effective rank-2 isotensor interaction, defined by off–shell pion–nucleon DCE scattering. In closure approximation pion potentials and two–nucleon correlations are obtained, similar to the neutrino potentials and the intranuclear exchange of Majorana neutrinos in 0ν2β Majorana double beta decay (MDBD).
The wide-field, multiplexed, spectroscopic facility WEAVE: Survey design, overview, and simulated implementation
(Royal Astronomical Society, 2023-03-11) Jin, Shoko; Trager, Scott C.; Dalton, Gavin B.; L. Aguerri, J. A.; Drew, J. E.; Falcón Barroso, Jesús; Oñorbe Bernis, José; Zurita, Cristina; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear
WEAVE, the new wide-field, massively multiplexed spectroscopic survey facility for the William Herschel Telescope, saw first light in late 2022. WEAVE comprises a new 2-deg field-of-view prime-focus corrector system, a nearly 1000-multiplex fibre positioner, 20 individually deployable ‘mini’ integral field units (IFUs), and a single large IFU. These fibre systems feed a dual-beam spectrograph covering the wavelength range 366–959 nm at R ∼ 5000, or two shorter ranges at ⁠. After summarizing the design and implementation of WEAVE and its data systems, we present the organization, science drivers, and design of a five- to seven-year programme of eight individual surveys to: (i) study our Galaxy’s origins by completing Gaia’s phase-space information, providing metallicities to its limiting magnitude for ∼3 million stars and detailed abundances for ∼1.5 million brighter field and open-cluster stars; (ii) survey ∼0.4 million Galactic-plane OBA stars, young stellar objects, and nearby gas to understand the evolution of young stars and their environments; (iii) perform an extensive spectral survey of white dwarfs; (iv) survey ∼400 neutral-hydrogen-selected galaxies with the IFUs; (v) study properties and kinematics of stellar populations and ionized gas in z < 0.5 cluster galaxies; (vi) survey stellar populations and kinematics in field galaxies at 0.3 ≲ z ≲ 0.7; (vii) study the cosmic evolution of accretion and star formation using >1 million spectra of LOFAR-selected radio sources; and (viii) trace structures using intergalactic/circumgalactic gas at z > 2. Finally, we describe the WEAVE Operational Rehearsals using the WEAVE Simulator.
COSMONAUT: A COmpact Spectrometer for Measurements of Neutrons at the ASDEX Upgrade Tokamak
(American Institute of Physics, 2024) Nocente, M.; Molin, A. D.; D Rigamonti, D.; Rosa, M. D.; Fernández Martínez, Begoña; Fugazza, S.; Guerrero Sánchez, Carlos; Gorini, G.; Kazakov, Y. O.; Tardini, G.; Tardocchi, M.; ASDEX Upgrade Team; Eurofus Tokamak Exploitat Team; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; European Union (UE); European Union (UE). H2020
A COmpact Spectrometer for Measurements Of Neutrons at the ASDEX Upgrade Tokamak (COSMONAUT) has been developed for spectroscopy measurements of the 2.45 MeV neutron emission from deuterium plasmas at the ASDEX Upgrade. The instrument is based on a CLYC-7 inorganic scintillator, whereby the detection of fusion neutrons occurs via their interaction with 35Cl nuclei in the detector crystal, leading to a peak in the detector response function and providing excellent neutron/gamma-ray discrimination capabilities. The diagnostics is installed along a radial line of sight and makes use of a digital system to record time resolved data for the whole duration of the discharge. Measurements in ASDEX Upgrade plasmas with neutral beam injection have been carried out and are successfully interpreted using state-of-the-art modeling codes. Next step applications of the diagnostics are in experiments aimed at generating energetic particles by ion cyclotron resonance heating schemes. In these scenarios, COSMONAUT will provide unique information on the acceleration of deuterons beyond the beam injection energy and on their confinement, for comparison with modeling.
2D Core Ion Temperature and Impurity Density Measurements with Coherence Imaging Charge Exchange Recombination Spectroscopy (CICERS) at Wendelstein 7-X (invited)
(American Institute of Physics, 2024) López Cansino, Ramón; Perseo, V.; Viezzer, Eleonora; Ford, O. P.; Kriete, M.; Romba, T.; Rueda Rueda, José; Poloskei, P. Z.; Reimold, F.; W7 X Team; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; European Union (UE). H2020; Ministerio de Ciencia e Innovación (MICIN). España; European Union (UE)
Coherence Imaging Charge Exchange Recombination Spectroscopy (CICERS) is an imaging diagnostic installed in Wendelstein 7-X from which 2D maps of ion temperature (Ti) and impurity density (nZ) are obtained. The improved spatial resolution and coverage, as compared to standard Charge eXchange Recombination Spectroscopy (CXRS), with which these parameters can be assessed, come at the expense of spectral resolution, requiring the development of new strategies to isolate the active charge exchange contribution from passive and Bremsstrahlung radiation. In this work, a new approach based on the modeling of background radiation is presented and applied to the derivation of 2D Ti maps. These are compared to the Ti profiles derived from standard CXRS, which found excellent agreement up to the edge (ρ > 0.8). The CICERS view is implemented in the pyFIDAsim code, which is used to provide further insight into the spatial localization of the radiation as measured by the diagnostic. Moreover, an absolute intensity calibration is carried out, and, coupled with pyFIDAsim, the first 2D nC maps are obtained and validated against CXRS data.
Understanding and Modeling of Gas Puff Injection for Diagnostic Purposes
(American Institute of Physics, 2025) Rodríguez González, A.; Cruz Zabala, Diego José; McKay, Kiera Anne; Griener, M.; Plank, U.; Viezzer, Eleonora; Rohde, V.; Dux, R.; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; European Union (UE). H2020
This article presents an experimental setup capable of providing high spatial and temporal resolution measurements of neutral gas puff injection using a glow discharge to excite the neutral gas and an ultra-high-speed camera to record the emitted light. Using the proposed setup, the shape and propagation velocity of a thermal deuterium gas puff at 1 bar have been measured. The cloud has a conical shape and a propagation velocity of vprop = 1870 ± 270 m/s. Furthermore, a code has been developed with the aim of studying the relation between the propagation velocity and the initial injection velocity of the gas. The simulations show that an initial injection velocity in the range of vinj ∼ 1650-1950 m/s can reproduce a propagation velocity of vprop = 1870 ± 270 m/s.
Mpemba Effect in Molecular Gases under Nonlinear Drag
(American Institute of Physics, 2020) Santos, Andrés; Prados Montaño, Antonio; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Agencia Estatal de Investigación. España; Junta de Extremadura
We look into the Mpemba effect - the initially hotter sample cools sooner - in a molecular gas with nonlinear viscous drag. Specifically, the gas particles interact among them via elastic collisions and with a background fluid at equilibrium. Thus, within the framework of kinetic theory, our gas is described by an Enskog-Fokker-Planck equation. The analysis is carried out using the first Sonine approximation, in which the evolution of temperature is coupled to that of excess kurtosis. This coupling leads to the emergence of the Mpemba effect, which is observed at an early stage of relaxation and when the initial temperatures of the two samples are close enough. This allows for the development of a simple theory, linearizing the temperature evolution around a reference temperature, namely, the initial temperature closer to the asymptotic equilibrium value. The linear theory provides a semiquantitative description of the effect, including expressions for crossover time and maximum temperature difference. We also discuss the limitations of our linearized theory.
Neutron-transfer induced breakup of the Borromean nucleus 9Be
(Elsevier, 2024-06-07) Villanueva, G; Moro Muñoz, Antonio Matías; Casal Berbel, Jesús; Lei, Jin; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España; National Natural Science Foundation of China
We address the problem of evaluating neutron-transfer induced breakup cross sections caused by the Borromean nucleus 9Be, using the reaction 197Au(9Be,8Be)198Au as a test case. This reaction was recently measured over a wide range of incident energies around the Coulomb barrier. To deal with the high density of 198Au states that can be potentially populated in this reaction, we employ the Ichimura, Austern, Vicent model, in which the spectrum of physical states for this system is replaced by the solutions of a complex n+197Au potential, accounting effectively for the fragmentation of single-particle states into physical states. Furthermore, to account for the unbound nature of the emitted 8Be system, we employ a three-body model of 9Be. The calculated stripping cross sections are found to be in good agreement with existing data over a wide range of incident energies. The importance of taking into account the energy spread of the single-particle strength of the outgoing 8Be and the target-like residual nucleus is discussed.

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