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arxiv: 2606.23169 · v1 · pith:HCB2WOFOnew · submitted 2026-06-22 · ⚛️ nucl-ex

Single Particle Excitations, Band Structures and Octupole Correlation in ⁶⁵Zn

Anil Sharma , S. Nandi , S. S. Dutta , S. Kundu , Pankaj K. Giri , A. Das , S. S. Ghugre , S. S. Nayak
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S. Basu S. Pal S. Das S. Dar S. Paul A. Pal S. Basak G. Mukherjee S. Bhattacharyya R. Raut
This is my paper

Pith reviewed 2026-06-26 05:56 UTC · model grok-4.3

classification ⚛️ nucl-ex
keywords zinc-65nuclear structuregamma-ray spectroscopyshell modelcollective excitationsoctupole correlationband structuressingle-particle excitations
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The pith

New gamma-ray data on zinc-65 reveal both single-particle excitations and collective band structures, including octupole correlations.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The study populates excited states in the zinc-65 nucleus through an alpha-induced reaction and records the emitted gamma rays with an array of Compton-suppressed detectors. Several previously unknown transitions are placed in the level scheme and multipolarities are assigned from angular distributions and polarization measurements, yielding updated spin and parity values. Measured energies and transition properties are compared with large-basis shell-model calculations in the p3/2-f5/2-p1/2-g9/2 space and with total Routhian surface calculations that map the nuclear shape. The resulting picture shows the coexistence of single-particle and collective excitations and illustrates how collectivity strengthens as additional nucleons occupy deformation-driving high-j orbitals outside a doubly magic core.

Core claim

The experimental level scheme of 65Zn exhibits both single-particle excitations and collective band structures. Shell-model calculations with two different interactions reproduce the measured energies when the model space includes the p3/2, f5/2, p1/2 and g9/2 orbitals. Total Routhian surface calculations for the associated deformations indicate the shapes responsible for the observed collective bands and support the presence of octupole correlations.

What carries the argument

Comparison of the observed gamma-ray transitions and level energies with large-basis shell-model calculations in the p3/2-f5/2-p1/2-g9/2 valence space together with Total Routhian Surface calculations that determine nuclear deformations.

If this is right

  • The level scheme of 65Zn contains both single-particle states and collective bands whose properties are reproduced by shell-model and TRS calculations.
  • Collectivity develops as nucleons occupy high-j orbitals outside the doubly magic core.
  • Octupole correlations appear in the collective excitations of this nucleus.
  • The structural evolution observed here is expected to continue in neighboring isotopes with additional valence nucleons.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same competition between single-particle and collective degrees of freedom should appear in the level schemes of nearby nuclei such as 66Zn or 64Zn.
  • The TRS surfaces could be used to predict the location of additional octupole-enhanced bands at higher spins.
  • Future lifetime measurements on the collective transitions would provide direct tests of the deformation parameters obtained from the TRS calculations.

Load-bearing premise

The multipolarities and electric or magnetic character of the observed gamma rays have been correctly determined by standard angular-correlation and polarization methods, allowing reliable spin-parity assignments.

What would settle it

A new measurement of the angular distribution or linear polarization for one of the key linking transitions that reverses its multipolarity and thereby changes the spin-parity assignment of a bandhead, breaking the agreement with the shell-model or TRS calculations.

Figures

Figures reproduced from arXiv: 2606.23169 by A. Das, Anil Sharma, A. Pal, G. Mukherjee, Pankaj K. Giri, R. Raut, S. Basak, S. Basu, S. Bhattacharyya, S. Dar, S. Das, S. Kundu, S. Nandi, S. Pal, S. Paul, S. S. Dutta, S. S. Ghugre, S. S. Nayak.

Figure 1
Figure 1. Figure 1: FIG. 1: The [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2: (a) Geometrical asymmetry ( [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3: Excitation scheme of [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5: Representative spectra projected out of [PITH_FULL_IMAGE:figures/full_fig_p006_5.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4: Representative spectra corresponding to gates ap [PITH_FULL_IMAGE:figures/full_fig_p006_4.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6: Spectra of 835-keV transition peak corresponding to [PITH_FULL_IMAGE:figures/full_fig_p009_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: FIG. 7: Evolution of excitation energy of the 3 [PITH_FULL_IMAGE:figures/full_fig_p009_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: FIG. 8: Comparison between experimental and shell model calculated level energies using JUN45 and JJ44B interactions. [PITH_FULL_IMAGE:figures/full_fig_p012_8.png] view at source ↗
Figure 9
Figure 9. Figure 9: FIG. 9: (a) Plot of excitation energy (E(I)) versus spin (I(I+1)) for rotational bands of the [PITH_FULL_IMAGE:figures/full_fig_p012_9.png] view at source ↗
Figure 10
Figure 10. Figure 10: FIG. 10: TRS plot of the 5/2 [PITH_FULL_IMAGE:figures/full_fig_p013_10.png] view at source ↗
Figure 11
Figure 11. Figure 11: FIG. 11: TRS plot of the 9/2 [PITH_FULL_IMAGE:figures/full_fig_p013_11.png] view at source ↗
Figure 12
Figure 12. Figure 12: FIG. 12: Excitation energy of the 2 [PITH_FULL_IMAGE:figures/full_fig_p014_12.png] view at source ↗
Figure 13
Figure 13. Figure 13: FIG. 13 [PITH_FULL_IMAGE:figures/full_fig_p014_13.png] view at source ↗
Figure 13
Figure 13. Figure 13: The B(E1, 1281 − keV )/B(E2, 858 − keV ) for the 65Zn, as extracted in this analysis, is ≈ 0.3×10−6 fm2 and is smaller than the same in 66,67Zn and in 71Ge. The latter has been evidenced [35] as an example of enhanced octupole correlation around N ≈ 40. V. CONCLUSION The level structure of the 65Zn nucleus was investi￾gated following its production in α-beam induced fusion￾evaporation reaction on 63Cu. Th… view at source ↗
read the original abstract

The excitation scheme of the $^{65}$Zn ($Z = 30, N = 35$) nucleus has been probed following its population in the $^{63}$Cu($\alpha$,pn) reaction at E$_{beam}$ = 30 MeV and using an array of Compton suppressed HPGe clovers as the detection system. This work has identified several new transitions of the nucleus and have modified the placements of some of the previously known ones. The multipolarities and the electric/ magnetic nature of the observed $\gamma$-ray rays have been measured, using the conventional methodologies. The spin-parity assignments for the levels have consequently been made; some of the spin-parities are new while others are either validation of the existing values or are modified results based on the present analysis. The experimental level scheme exhibits collective as well as single particle structures. The measured level energies have been compared with those calculated in the framework of the large basis shell model using a model space of $p_{3/2}, f_{5/2}, p_{1/2}, g_{9/2}$ orbitals and two different interactions. The collective excitations of the nucleus were probed through the properties of its band structures and through the calculations of the Total Routhian Surface (TRS) for the associated deformations/ shapes. The results of this study brings out the essential features of evolving structural characteristics and developing collectivity with increasing number of nucleons outside a doubly-magic core and with their occupancy of deformation driving high-$j$ orbitals.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The paper reports an experimental study of the level scheme of 65Zn populated in the 63Cu(α,pn) reaction at 30 MeV using Compton-suppressed HPGe clovers. Several new γ-ray transitions are identified and some prior placements revised. Multipolarities and E/M character are determined via conventional methods, enabling spin-parity assignments (some new, some revised). The resulting level scheme is compared to large-basis shell-model calculations in the p3/2-f5/2-p1/2-g9/2 space with two interactions, and collective features are examined via band properties and Total Routhian Surface (TRS) calculations. The work concludes that the structure exhibits both single-particle and collective excitations, illustrating evolving collectivity with increasing nucleons outside the 56Ni core and occupancy of high-j orbitals.

Significance. If the spin-parity assignments hold, the results add to the systematics of structure evolution in the A≈65 region near the N=Z=28 closure, providing new data on the interplay between single-particle excitations and emerging collectivity driven by high-j orbitals. The use of standard experimental techniques and direct comparison to established shell-model interactions and TRS calculations strengthens the nuclear-structure database for Zn isotopes.

major comments (2)
  1. [Experimental results / level scheme] Experimental results section: the spin-parity assignments that underpin all structural interpretations (collective vs. single-particle bands, model comparisons) rest on multipolarity determinations stated to follow 'conventional methodologies,' yet the manuscript provides no tabulated DCO ratios, angular-distribution coefficients, or polarization asymmetries for the key transitions. Without these observables the assignments cannot be independently verified and remain the load-bearing step for the central claim.
  2. [Shell-model calculations] Shell-model comparison section: level energies are compared to calculations with two interactions, but no quantitative measure of agreement (rms deviation, χ² per degree of freedom, or tabulated energy differences) is given. This weakens the assertion that the data validate the model space and interactions.
minor comments (2)
  1. [Abstract] Abstract: grammatical errors ('have identified', 'γ-ray rays', 'brings out') and missing quantitative indicators of data quality (fit metrics, error bars) should be corrected.
  2. [Theoretical calculations] Notation: the model space is listed as p3/2, f5/2, p1/2, g9/2 but the effective charges or truncation scheme used in the calculations are not stated explicitly.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful review and constructive comments. We address each major comment below.

read point-by-point responses

  1. Referee: [Experimental results / level scheme] Experimental results section: the spin-parity assignments that underpin all structural interpretations (collective vs. single-particle bands, model comparisons) rest on multipolarity determinations stated to follow 'conventional methodologies,' yet the manuscript provides no tabulated DCO ratios, angular-distribution coefficients, or polarization asymmetries for the key transitions. Without these observables the assignments cannot be independently verified and remain the load-bearing step for the central claim.

    Authors: We agree that the supporting observables for the multipolarity assignments were omitted. In the revised manuscript we will add a table of DCO ratios, angular-distribution coefficients and polarization asymmetries for the key transitions, together with the deduced multipolarities and spin-parity assignments, enabling independent verification. revision: yes

  2. Referee: [Shell-model calculations] Shell-model comparison section: level energies are compared to calculations with two interactions, but no quantitative measure of agreement (rms deviation, χ² per degree of freedom, or tabulated energy differences) is given. This weakens the assertion that the data validate the model space and interactions.

    Authors: We acknowledge the absence of quantitative metrics. While visual level-scheme comparisons are common, we will calculate and report the rms deviations between experimental and calculated energies for both interactions, together with a brief discussion of the agreement, in the revised manuscript. revision: yes

Circularity Check

0 steps flagged

No circularity: experimental assignments and model comparisons remain independent of fitted inputs or self-citation chains.

full rationale

The paper reports new transitions and multipolarity measurements via standard ('conventional') techniques, followed by spin-parity assignments and direct comparison of measured level energies to shell-model calculations that employ two published interactions in a fixed model space. TRS calculations are likewise described as standard probes of collective shapes. No parameters are fitted to the present dataset and then relabeled as predictions; no self-citation supplies a uniqueness theorem or ansatz that bears the central claim; the experimental observables (level scheme, gamma-ray properties) are not redefined in terms of the model outputs. The derivation chain therefore does not reduce to its own inputs by construction.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The central claim rests on the accuracy of gamma-ray multipolarity assignments and the applicability of the chosen model space and interactions; no new entities are postulated.

axioms (2)
  • domain assumption The 63Cu(alpha,pn) reaction at 30 MeV populates the observed states without significant contamination from other channels.
    Invoked to attribute all observed transitions to 65Zn.
  • domain assumption Conventional angular-correlation and polarization methods yield unambiguous multipolarity assignments.
    Used to convert gamma-ray data into spin-parity values.

pith-pipeline@v0.9.1-grok · 5890 in / 1444 out tokens · 28535 ms · 2026-06-26T05:56:16.938552+00:00 · methodology

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