Unstable heavy atomic nuclei not found in nature can be created by fusing two stable nuclei, in a process analogous to colliding charged droplets of liquid. Recently, the formation of a handful of super-heavy nuclei with atomic numbers 114 (ref. 1) and 116 (ref. 2) has been achieved by fusion of heavy nuclei. The electrostatic energy of such systems is very large (which is the reason super-heavy nuclei are unstable), so although the two nuclei may initially be captured by the nuclear potential, rather than fusing, they almost always separate after transfer of mass to the lighter nucleus. This process, called quasi-fission3,4, can inhibit fusion by many orders of magnitude. Understanding this inhibition may hold the key to forming more super-heavy elements. Theoretically, inhibition is predicted (ref. 5 and references therein) when the product Z1Z2 of the charges of the projectile and target nuclei is larger than about 1,600. Here we report measurements of three fusion reactions with Z1Z2 around half this value, each forming 216 88Ra. We find convincing model-independent evidence both of inhibition of fusion, and of the presence of quasi-fission. These results defy interpretation within the standard picture of nuclear fusion and fission.

Unexpected inhibition of fusion in nucleus–nucleus collisions

The excitation functions for production of many residues in the fusion of $^{12}\mathrm{C}$ with $^{181}\mathrm{Ta}$ and $^{197}\mathrm{Au}$ and of $^{16}\mathrm{O}$ with $^{165}\mathrm{Ho}$ and $^{181}\mathrm{Ta}$ have been measured at incident energies varying from the Coulomb barrier up to about 10 MeV/nucleon. The cross sections for fusion of these ions without fission have been deduced and they show that such a process may only occur for projectile angular momenta smaller than a critical value. The excitation functions for individual reactions provide evidence for the emission of preequilibrium nucleons during the thermalization of the composite nucleus and may be satisfactorily reproduced by a calculation based on the Boltzmann master equation theory.

Study of the reactions occurring in the fusion of 12C and 16O with heavy nuclei at incident energies below 10 MeV/nucleon.

Experiments have been carried out to explore the reaction dynamics leading to incomplete fusion of heavy ions at moderate excitation energies. Excitation functions for $^{168}\mathrm{Lu}$${}^{\mathrm{m}}$, $^{167}\mathrm{Lu}$, $^{167}\mathrm{Yb}$, $^{166}\mathrm{Tm}$, $^{179}\mathrm{Re}$, $^{177}\mathrm{Re}$, $^{177}\mathrm{W}$, $^{178}\mathrm{Ta}$, and $^{177}\mathrm{Hf}$ radio-nuclides populated via complete and/or incomplete fusion of $^{16}\mathrm{O}$ with $^{159}\mathrm{Tb}$ and $^{169}\mathrm{Tm}$ have been studied over the wide projectile energy range ${E}_{\mathrm{proj}}\ensuremath{\approx}75\text{\ensuremath{-}}95$ MeV. Recoil-catcher technique followed by off-line \ensuremath{\gamma}-spectrometry has been employed in the present measurements. Experimental data have been compared with the predictions of theoretical model code PACE2. The experimentally measured production cross sections of \ensuremath{\alpha}-emitting channels were found to be larger as compared to the theoretical model predictions and may be attributed to incomplete fusion at these energies. During the analysis of experimental data, incomplete fusion has been found to be competing with complete fusion. As such, an attempt has been made to estimate the incomplete fusion fraction for both the systems, and has been found to be sensitive for projectile energy and mass asymmetry of interacting partners.

Influence of incomplete fusion on complete fusion: Observation of a large incomplete fusion fraction at E ≅5-7 MeV/nucleon

This experiment has been done with a view to studying complete and incomplete fusion in heavy-ion-induced reactions. Excitation functions for several reactions induced by ${}^{12}{\mathrm{C}}^{5+}$ ions on ${}^{165}\mathrm{Ho}$ at incident energies from 55 to 80 MeV have been measured using the activation technique. The analysis of the data has been done using the codes ALICE-91 and CASCADE. The parameter ${F}_{\ensuremath{\theta}},$ the ratio of actual moment of inertia to the rigid-body value, has been found to play an important role in the calculations done by the code CASCADE. Significant contributions from both the complete and the incomplete fusion channels have been observed. Further, in the case of the reaction $(\mathrm{C},p3n)$ considerable contribution from the decay of higher charge isobar precursor has been observed.

Complete and incomplete fusion of 12 C with 165 Ho below 7 MeV/nucleon: Measurements and analysis of excitation functions

The excitation functions for production of 21 isotopes and isomers of Au, Pt, Ir, Os and Re in the interaction of12C with181Ta from 54 to 98 MeV incident energy have been measured by the activation technique. The analysis of these data allows one to estimate the reaction cross-section and the cross-sections for complete fusion of12C and the incomplete fusion of8Be and α fragments with tantalum.

Excitation functions for production of heavy residues in the interaction of12C with181Ta

The excitation functions for production of nineteen isotopes of At, Po, Bi, Pb, and Tl in the interaction of $^{12}\mathrm{C}$ with $^{197}\mathrm{Au}$ between 57 and 97 MeV incident energy have been measured with the activation technique. The analysis of these data allows one to estimate the cross sections for complete fusion of $^{12}\mathrm{C}$ and incomplete fusion of $^{8}\mathrm{Be}$ and \ensuremath{\alpha} fragments with gold, and shows the presence of preequilibrium emissions at incident energies only slightly higher than the Coulomb barrier acting between $^{12}\mathrm{C}$ and $^{197}\mathrm{Au}$.

Complete and incomplete fusion and emission of preequilibrium nucleons in the interaction of C 12 with Au 197 below 10 MeV/nucleon

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

E. Vaciago

Author Tools

Chat about Author

Papers

Complete and incomplete fusion and emission of preequilibrium nucleons in the interaction of C 12 with Au 197 below 10 MeV/nucleon