A Question of Shape: New Mechanism Governing Superheavy Nuclei Survival

A. Rahmatinejad; G. G. Adamian; M. Kowal; N. V. Antonenko; P. Jachimowicz; T. M. Shneidman

arxiv: 2605.27940 · v1 · pith:2SWURXX6new · submitted 2026-05-27 · ⚛️ nucl-th

A Question of Shape: New Mechanism Governing Superheavy Nuclei Survival

A. Rahmatinejad , T. M. Shneidman , G. G. Adamian , N. V. Antonenko , P. Jachimowicz , M. Kowal This is my paper

Pith reviewed 2026-06-29 09:56 UTC · model grok-4.3

classification ⚛️ nucl-th

keywords superheavy nucleinuclear shapefinite temperatureshell correctionssurvival probabilityfissiondeformationJahn-Teller effect

0 comments

The pith

Hot superheavy nuclei equilibrate in deformed shapes at finite excitation energies instead of remaining spherical.

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

The paper shows that traditional assumptions of spherical shapes for hot superheavy nuclei are incorrect because spherical configurations have high degeneracy in single-particle levels near the Fermi surface. This causes their shell corrections to damp out much faster with rising temperature than those of deformed nuclei. Consequently, at excitations of 30 to 50 MeV in the Z equals 118 to 120 region, the potential energy landscape inverts and deformed minima become preferred. This shape change alters the rates of neutron evaporation versus fission, leading to a deformation-dependent adjustment in calculated survival probabilities. Models relying on spherical ground-state properties therefore carry a systematic bias.

Core claim

Hot superheavy nuclei do not retain spherical shapes but equilibrate in deformed, often oblate or triaxial, configurations at finite excitation energy. This arises from a Jahn-Teller analog mechanism where spherical systems' high single-particle degeneracy makes shell corrections damp faster with temperature. In the Z=118-120 region this causes a thermally induced inversion of the potential-energy landscape, favoring deformed minima at U=30-50 MeV and changing the competition between neutron evaporation and fission. A deformation-dependent correction to the survival probability is derived, exposing bias in spherical-based estimates.

What carries the argument

The temperature-dependent damping of shell corrections driven by single-particle level degeneracy, leading to shape inversion via a Jahn-Teller-like effect.

If this is right

Thermally induced inversion where deformed minima are favored at U=30-50 MeV for Z=118-120.
Altered competition between neutron evaporation and fission.
Need for a deformation-dependent correction to survival probability.
Systematic bias revealed in estimates based on spherical ground-state properties.
Revision called for in current models of superheavy-nucleus synthesis and decay.

Where Pith is reading between the lines

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

Future synthesis experiments may need to account for temperature-dependent shapes to match observed yields.
Level density measurements in hot nuclei could provide a test of the assumed damping rates.
The effect might extend to other regions of the nuclear chart where shell effects are important at finite temperature.

Load-bearing premise

The rates at which shell corrections damp with temperature depend primarily on the degeneracy of single-particle levels near the Fermi surface in spherical versus deformed nuclei.

What would settle it

A direct measurement showing that survival probabilities for Z=118-120 nuclei at 30-50 MeV excitation match spherical-model predictions rather than the deformation-corrected ones, or spectroscopic evidence of persistent spherical shapes in hot superheavy nuclei.

Figures

Figures reproduced from arXiv: 2605.27940 by A. Rahmatinejad, G. G. Adamian, M. Kowal, N. V. Antonenko, P. Jachimowicz, T. M. Shneidman.

**Figure 1.** Figure 1: maps the ground-state quadrupole deformation β20 for cold SHN, calculated via our macroscopicmicroscopic approach assuming axial symmetry [14]. The FIG. 1. Landscape of ground-state quadrupole deformations β20 for superheavy nuclei. The data are adapted from the macroscopic-microscopic calculations in Ref. [14]. landscape is topologically complex, featuring spherical, well-deformed prolate, oblate, and s… view at source ↗

**Figure 2.** Figure 2: FIG. 2 [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗

**Figure 4.** Figure 4: FIG. 4 [PITH_FULL_IMAGE:figures/full_fig_p004_4.png] view at source ↗

**Figure 3.** Figure 3: FIG. 3 [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗

read the original abstract

We demonstrate that hot superheavy nuclei do not retain spherical shapes, as traditionally assumed, but instead equilibrate in deformed, often oblate or triaxial, configurations at finite excitation energy. This behavior arises from a mechanism analogous to the Jahn-Teller effect: spherical systems exhibit high single-particle degeneracy near the Fermi surface, causing their shell corrections to damp out significantly faster with temperature than those of deformed shapes. Using a finite-temperature framework, we reveal a thermally induced inversion of the potential-energy landscape in the Z = 118-120 region, where deformed minima become energetically favored at U = 30-50 MeV. This shape inversion fundamentally alters the competition between neutron evaporation and fission. We derive a deformation-dependent correction to the survival probability, revealing a systematic bias in estimates based on spherical ground-state properties. Our results identify a finite-temperature structural effect that calls for a revision of current models of superheavy-nucleus synthesis and decay.

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.

Desk Editor's Note private letter to a colleague

The paper flags a possible temperature-driven shape inversion in hot superheavy nuclei that would bias survival probabilities, but the damping rates rest on unbenchmarked inputs.

read the letter

The main takeaway is that spherical shell corrections in superheavy nuclei damp faster with temperature than deformed ones because of higher level degeneracy near the Fermi surface. This leads to an inversion where oblate or triaxial shapes become preferred at 30-50 MeV excitation, which then changes the evaporation-fission balance and requires a correction to standard survival probabilities.

The new piece is the explicit link between that degeneracy effect and a systematic shift in the potential landscape for Z=118-120 nuclei. The authors treat it as a finite-temperature Jahn-Teller analog and show how it alters the competition between channels. That framing is not in the usual spherical-ground-state calculations, so it flags a possible bias worth testing.

The calculation is presented cleanly enough that a reader can see where the correction enters the survival formula. If the underlying single-particle spectra and temperature dependence hold, the result would matter for anyone modeling cross sections at current facilities.

The weak point is the damping itself. The faster washout for spherical configurations is asserted from degeneracy but not derived or calibrated against measured level densities in this work. Pairing, continuum coupling, or the precise smoothing width could easily change the relative rates, and nothing in the abstract or stress-test note shows an independent check or error estimate. Without that, the size of the inversion stays provisional.

This is for modelers who already use temperature-dependent barriers in superheavy synthesis codes. A referee could usefully ask for the explicit damping functions and a comparison to any available finite-temperature data. I would send it to review so the quantitative steps can be examined rather than desk-reject it on the abstract alone.

Referee Report

1 major / 1 minor

Summary. The paper claims that hot superheavy nuclei (Z=118-120) do not retain spherical shapes at finite excitation energy but equilibrate in deformed (often oblate or triaxial) configurations. This arises from a Jahn-Teller-analog mechanism in which spherical single-particle spectra near the Fermi surface produce shell corrections that damp materially faster with temperature than those of deformed shapes, producing a thermally driven inversion of the potential-energy landscape at U=30-50 MeV. The authors derive a deformation-dependent correction to the survival probability, arguing that this introduces a systematic bias in estimates based on spherical ground-state properties.

Significance. If substantiated, the result would be significant for superheavy-element synthesis modeling because it supplies an explicit, deformation-dependent correction to survival probabilities arising from finite-temperature structural effects. The manuscript gives credit to the derivation of this correction term and identifies a concrete, falsifiable prediction (shape preference at moderate excitation) that could be tested against level-density data.

major comments (1)

[Finite-temperature framework] Finite-temperature framework section: the damping rates of shell corrections with temperature (driven by single-particle level degeneracy) are adopted without an independent derivation or direct calibration against measured level densities. This assumption is load-bearing for the central claim that spherical configurations damp faster than deformed ones, producing the landscape inversion at U=30-50 MeV and the subsequent correction to survival probability.

minor comments (1)

[Abstract] Abstract: the range of nuclei and the precise single-particle model employed are not stated, which would help readers assess the generality of the reported shape inversion.

Simulated Author's Rebuttal

1 responses · 1 unresolved

We thank the referee for the constructive comment on the finite-temperature framework. We address the concern regarding the adoption of damping rates below, providing clarification on their origin while acknowledging limitations in experimental calibration.

read point-by-point responses

Referee: Finite-temperature framework section: the damping rates of shell corrections with temperature (driven by single-particle level degeneracy) are adopted without an independent derivation or direct calibration against measured level densities. This assumption is load-bearing for the central claim that spherical configurations damp faster than deformed ones, producing the landscape inversion at U=30-50 MeV and the subsequent correction to survival probability.

Authors: The damping rates follow from the standard finite-temperature extension of the Strutinsky shell-correction formalism, in which the temperature-dependent factor is determined by the single-particle level density g(ε_F) at the Fermi surface. The faster damping for spherical configurations is a direct consequence of the higher degeneracy computed from our self-consistent single-particle spectra, rather than an external parameter choice. We will revise the manuscript to include an explicit derivation of the damping factor from g(ε_F) and its deformation dependence, citing the foundational references for the general method. Direct calibration against measured level densities for Z=118-120 is not feasible, as no such data exist; the framework is instead anchored in established systematics for lighter nuclei and the internal consistency of the calculated spectra. revision: partial

standing simulated objections not resolved

Direct calibration of damping rates against measured level densities for Z=118-120 nuclei cannot be performed, as no experimental data are available in this region.

Circularity Check

0 steps flagged

No significant circularity detected

full rationale

The provided abstract and context describe a physical mechanism rooted in single-particle degeneracy causing differential damping of shell corrections with temperature, leading to shape inversion in a finite-temperature framework. No equations, parameter fits, or self-citations are exhibited that reduce the central claim (thermally driven deformation preference and survival correction) to an input by construction, a renamed fit, or a load-bearing self-citation chain. The derivation is presented as following from standard nuclear structure considerations without evident self-referential reduction, qualifying as self-contained.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract-only review means the ledger cannot be populated from explicit equations or sections; the central claim rests on an unstated finite-temperature single-particle model and an assumed damping law for shell corrections.

pith-pipeline@v0.9.1-grok · 5720 in / 1106 out tokens · 15757 ms · 2026-06-29T09:56:16.954053+00:00 · methodology

discussion (0)

Reference graph

Works this paper leans on

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