Search for excited states in O25
| Autor: | Nicolas Michel, Jimmy Rotureau, K. Stiefel, Witold Nazarewicz, Joseph E. Finck, Nathan Frank, J. K. Smith, Sharon L. Stephenson, Remco Zegers, Anthony Kuchera, Paul DeYoung, Michael Thoennessen, K. Fossez, M. D. Jones, Thomas Baumann |
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| Rok vydání: | 2017 |
| Předmět: |
Physics
education.field_of_study Proton 010308 nuclear & particles physics Density matrix renormalization group Population Parity (physics) Configuration interaction 01 natural sciences 7. Clean energy Excited state 0103 physical sciences Bound state Atomic physics 010306 general physics Ground state education |
| Zdroj: | Physical Review C. 96 |
| ISSN: | 2469-9993 2469-9985 |
| Popis: | Background: Theoretical calculations suggest the presence of low-lying excited states in $^{25}\mathrm{O}$. Previous experimental searches by means of proton knockout on $^{26}\mathrm{F}$ produced no evidence for such excitations.Purpose: We search for excited states in $^{25}\mathrm{O}$ using the $^{24}\mathrm{O}(d,p)^{25}\mathrm{O}$ reaction. The theoretical analysis of excited states in unbound $^{25,27}\mathrm{O}$ is based on the configuration interaction approach that accounts for couplings to the scattering continuum.Method: We use invariant-mass spectroscopy to measure neutron-unbound states in $^{25}\mathrm{O}$. For the theoretical approach, we use the complex-energy Gamow Shell Model and Density Matrix Renormalization Group method with a finite-range two-body interaction optimized to the bound states and resonances of $^{23--26}\mathrm{O}$, assuming a core of $^{22}\mathrm{O}$. We predict energies, decay widths, and asymptotic normalization coefficients.Results: Our calculations in a large $spdf$ space predict several low-lying excited states in $^{25}\mathrm{O}$ of positive and negative parity, and we obtain an experimental limit on the relative cross section of a possible ${J}^{\ensuremath{\pi}}={1/2}^{+}$ state with respect to the ground state of $^{25}\mathrm{O}$ at ${\ensuremath{\sigma}}_{1/2+}/{\ensuremath{\sigma}}_{g.s.}=0.{25}_{\ensuremath{-}0.25}^{+1.0}$. We also discuss how the observation of negative parity states in $^{25}\mathrm{O}$ could guide the search for the low-lying negative parity states in $^{27}\mathrm{O}$.Conclusion: Previous experiments based on the proton knockout of $^{26}\mathrm{F}$ suffered from the low cross sections for the population of excited states in $^{25}\mathrm{O}$ because of low spectroscopic factors. In this respect, neutron transfer reactions carry more promise. |
| Databáze: | OpenAIRE |
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