Robustness of the excitation energy at scission as a novel probe of nuclear dissipation at high energy

2012 ◽  
Vol 86 (3) ◽  
Author(s):  
W. Ye ◽  
N. Wang
Keyword(s):  
Excitation Energy ◽  
High Energy ◽  
Nuclear Dissipation

γ probe of nuclear dissipation

2014 ◽  
Vol 23 (06) ◽  
pp. 1460003 ◽  
Author(s):  
Ye Wei
Keyword(s):  
Excitation Energy ◽  
Giant Dipole Resonance ◽  
System Size ◽  
High Energy ◽  
Large System ◽  
Langevin Model ◽  
Dipole Resonance ◽  
Γ Ray ◽  
Nuclear Dissipation ◽  
Large System Size

The Langevin model is applied to investigate the roles of excitation energy and system size in the evolution of post-saddle giant dipole resonance (GDR) γ-ray multiplicity (Mγ) with post-saddle friction strength (β). It is demonstrated that Mγ is more sensitive to β at high energy. Furthermore, it is shown that the dependence of γ emission on friction is sensitive to the size of fissioning nuclei, and a large system size significantly increases the sensitivity. Our findings indicate that in experiments, to tightly constrain post-saddle dissipation through the γ probe, it is optimal to produce heavy fissioning systems with high energy.

scholarly journals Ultrafast charge transfer dynamics in 2D Covalent Organic Frameworks/Re-complex hybrid photocatalyst for CO2 reduction: hot electrons vs. cold electrons

2021 ◽  
Author(s):  
Qinying Pan ◽  
Mohamed Abdellah ◽  
Yuehan Cao ◽  
Yang Liu ◽  
Weihua Lin ◽  
...  
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Excitation Energy ◽  
Co2 Reduction ◽  
Underlying Mechanism ◽  
High Energy ◽  
Hot Electrons ◽  
Covalent Organic Frameworks ◽  
Energy Excitation ◽  
Energy Dependent

Abstract Rhenium(I)-carbonyl-diimine complexes are promising photocatalysts for CO2 reduction. Covalent organic frameworks (COFs) can be perfect sensitizers to enhance the reduction activities. Here we investigated the excited state dynamics of COF (TpBpy) with 2,2'-bipyridine incorporating Re(CO)5Cl (Re-TpBpy) to rationalize the underlying mechanism. The time-dependent DFT calculation first clarified excited state structure of the hybrid catalyst. The studies from transient visible and infrared spectroscopies revealed the excitation energy-dependent photo-induced charge transfer pathways in Re-TpBpy. Under low energy excitation, the electrons at the LUMO level are quickly injected from Bpy into ReI center (1–2 ps) followed by backward recombination (13 ps). Under high energy excitation, the hot-electrons are first injected into the higher unoccupied level of ReI center (1–2 ps) and then slowly relax back to the HOMO in COF (24 ps). There also remains long-lived free electrons in the COF moiety. This explained the excitation energy-dependent CO2 reduction performance in our system.

Inference on fission timescale from neutron multiplicity measurement in18O+184W

2022 ◽  
Author(s):  
Niraj Kumar Rai ◽  
Aman Gandhi ◽  
M T Senthil Kannan ◽  
Sujan Kumar Roy ◽  
Saneesh Nedumbally ◽  
...  
Keyword(s):  
Excitation Energy ◽  
Beam Energy ◽  
Incident Beam ◽  
Fission Process ◽  
Incident Beam Energy ◽  
Neutron Evaporation ◽  
Neutron Multiplicities ◽  
Nuclear Dissipation ◽  
Fission Yields ◽  
Primary Compound

Abstract The pre-scission and post-scission neutron multiplicities are measured for the 18O + 184W reaction in the excitation energy range of 67.23−76.37 MeV. Langevin dynamical calculations are performed to infer the energy dependence of fission decay time in compliance with the measured neutron multiplicities. Different models for nuclear dissipation are employed for this purpose. Fission process is usually expected to be faster at a higher beam energy. However, we found an enhancement in the average fission time as the incident beam energy increases. It happens because a higher excitation energy helps more neutrons to evaporate that eventually stabilizes the system against fission. The competition between fission and neutron evaporation delicately depends on the available excitation energy and it is explained here with the help of the partial fission yields contributed by the different isotopes of the primary compound nucleus.

scholarly journals Study of High-Energy Fission in Inverse Kinematics

2019 ◽  
Vol 223 ◽  
pp. 01037
Author(s):  
G. Mantovani ◽  
D. Ramos ◽  
M. Caamaño ◽  
A. Lemasson ◽  
M. Rejmund ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Excitation Energy ◽  
Shell Structure ◽  
Inverse Kinematics ◽  
High Energy ◽  
Total Kinetic Energy ◽  
High Excitation Energy ◽  
High Excitation ◽  
Shell Effects

Fission at low excitation energy, is a process in which both macroscopic and microscopic aspects are involved. Some features in the total kinetic energy and in the N/Z distributions of the fragments, commonly associated with shell effects, came out in a series of recent experiments with high excitation energy fusionfission reactions in inverse kinematics. In the latest experiment of this campaign, a study of high-energy fission and quasi-fission between a 238U beam and a series of light targets was carried out by using the aforementioned technique, in order to probe the role of the shell structure in these processes.

Fluorescence analysis during steady-state photosynthesis

1989 ◽  
Vol 323 (1216) ◽  
pp. 253-268 ◽  
Keyword(s):  
Steady State ◽  
Excitation Energy ◽  
Fluorescence Analysis ◽  
High Energy ◽  
Photosynthetic Gas Exchange ◽  
Acceptor Side ◽  
Thioredoxin System ◽  
Psii Photochemistry ◽  
Photosynthetic Control ◽  
Absorbance Changes

Photosynthetic gas exchange of attached leaves has been measured under steady-state conditions at different light intensities and correlated with simultaneous measurements of chlorophyll fluorescence and oxidized P 700 (by absorbance changes at 820 nm). The data suggest that during light-saturated assimilation, photosystem II (PSII) photochemistry is mainly controlled by non-photochemical and non-radiative dissipation of excitation energy, rather than by accumulation of reduced acceptor, Q A , and this could be related to ‘high-energy quenching’ of fluorescence. The occurrence of oxidized P 700 at saturating light and low concentration of CO 2 suggests that in the steady state PSI photochemistry is controlled by a shortage of electron donation from the plastoquinone pool (photosynthetic control), rather than by excess electrons at the acceptor side. The significance of the oxidized form of P 700 as a ‘quencher’ of excitation energy is discussed. This control of photosystems I and II, both related to the proton gradient across the thylakoid membrane, may serve to match the potential rate of net photochemistry to the demand by the biochemical reactions. However, when light-saturated assimilation is not limited by CO 2 , PSI activity is controlled by accumulation of reduced electron acceptors, rather than by photosynthetic mechanisms. Photosynthetic control has been found to determine the redox state of the ferredoxin-thioredoxin system.

scholarly journals Determination of GT-transition Strengths in \(A=34\) Isobars Using Charge Exchange \((^3\text{He},t)\) Reaction

2012 ◽  
Vol 22 (1) ◽  
pp. 91-96
Author(s):  
Nguyen Tuan Khai ◽  
Bui Duy Linh ◽  
Tran Duc Thiep ◽  
Y. Fujita ◽  
T Adachi ◽  
...  
Keyword(s):  
Excitation Energy ◽  
Excited States ◽  
Ground State ◽  
Incident Energy ◽  
High Energy ◽  
High Energy Resolution ◽  
Good Quantum Number ◽  
Gamow Teller ◽  
Good Agreement

Under the assumption that isospin \(T\) is a good quantum number, mirror transitions \(T_{z }= +1 \to  0\) and \(T_{z }= -1  \to  0\) were studied in \(A = 34\) isobars, where \(T_{z}\) is \(z\) component of iospin \(T\) and is defined by \(T_{z} = (N-Z)/2\). With a high energy resolution of 35 keV in \(^{34}\)S\((^{3}He,t)^{34}\)Cl reaction measurement at \(0^{\circ}\) scattering angle and at an incident energy of 140 MeV/nucleon, strengths of Fermi and Gamow-Teller (GT) transitions from the \(J^{\pi } = 0^{ + }\), \(T_{z }= +1\) ground state of \(^{34}\)S to the \(J^{\pi } = 1^{+ }\), \(T_{z }= 0\) excited states in \(^{34}\)Cl were determined up to excitation energy \((E_{x})\) of \(7.08\) MeV. The corresponding isospin-symmetric transitions connecting \(T_{z }= -1\) and \(T_{z }= 0\) states can be studied in the \(^{34}\)Ar \(\beta ^{ + }\) decay. The strengths of the \((GT)_{\pm }\) transitions were compared up to the excitation energy of 3.1 MeV. A good agreement was observed for two strong transitions to \(2.580\) MeV and \(3.129\) MeV states, while a disagreement about \(45\text{%}\) was observed for a weaker transition to \(0.666\) MeV low-lying state.

Nonstatistical fluctuations of target fragments emitted in high-energy nucleus–nucleus collisions

2002 ◽  
Vol 80 (2) ◽  
pp. 119-128
Author(s):  
N N Abd-Allah
Keyword(s):  
Excitation Energy ◽  
Impact Parameter ◽  
Target Nucleus ◽  
Incident Energy ◽  
Nuclear Emulsion ◽  
Residual Nucleus ◽  
High Energy ◽  
Critical Value ◽  
Nucleus Interaction ◽  
The Impact

Analysis of target-fragmented "black" particles in nuclear emulsion from high-energy relativistic interactions initiated by 28Si at 4.5 A GeV/c is investigated. The number of slowly emitted particles from the struck target nucleus is considered as a measure of the degree of excitation of the residual nucleus. This number shows a constant critical value, with the degree of the impact parameter or the degree of excitation. The target evaporation particles of nucleus–nucleus interaction reveal the existence of nonstatistical fluctuations in the azimuthal plane of the interaction. The asymmetry or nonstatistical fluctuations, while found to be independent of projectile mass or incident energy, are dependent on the excitation energy of the target nucleus. A multiparticle correlation is observed between created particles as well as target fragments. This assumes production of clusters. These clusters seem to be formed during the decoloring process. PACS No.: 25.70Mn

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