Reconciling anomalous quadrupole deformation in ^200,202Hg with Coulomb excitation

Abstract

Stable isotopes of mercury, with two fewer protons than magic lead, are found experimentally to exhibit oblate deformation, similar to neighbouring platinum isotopes. These isotopes are of special interest due to the use of ¹⁹⁹Hg as an experimental laboratory for electric dipole moment searches, which are a powerful test of charge-parity (CP) violation and the interpretation of which depends critically on the quadrupole and octopule shapes of the underlying nucleus. It is observed that the ratio between experimental quadrupole moments and electric quadrupole transition strengths exceed physical limits, placing uncertainty on this underlying shape. In an effort to resolve this situation, a Coulomb excitation experiment was performed to remeasure the spectroscopic quadrupole moment (Q_s(2⁺₁)) of ²⁰⁰Hg and ²⁰²Hg utilising ⁴⁸Ti and ¹²⁰Sn targets. The values obtained were Q_s(2⁺₁) ^200,202Hg = 0.52(14), 0.63(10) eb, lying within physical limits defined by B(E2) values but still consistent with near axially-symmetric oblate deformation. A systematic study of nuclei indicates that, as with neighbouring Pt isotopes, ^200,202Hg are strongly oblate deformed, albeit without fully developing into an axial rotor.

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BibTeX RIS

BibTeX

@misc{willmott2026reconciling,
  title = {{Reconciling anomalous quadrupole deformation in $^200,202$Hg with Coulomb excitation}},
  author = {G. Willmott and J. Heery and J. Henderson and P. Stevenson and C. Cousins and D. T. Doherty and A. Ertoprak and B. P. Kay and L. Morrison and C. Mueller-Gatermann and C. O'Shea and P. H. Regan and W. Reviol and D. M. Rhodes and R. Russell and N. Sensharma and D. Seweryniak and M. Siciliano and R. S. Sidhu and I. A. Tolstukhin and C. Y. Wu},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.28202},
  eprint = {2610.28202},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.28202},
  note = {CC BY-NC-ND 4.0},
}

RIS

TY  - UNPB
TI  - Reconciling anomalous quadrupole deformation in ^200,202Hg with Coulomb excitation
AU  - G. Willmott
AU  - J. Heery
AU  - J. Henderson
AU  - P. Stevenson
AU  - C. Cousins
AU  - D. T. Doherty
AU  - A. Ertoprak
AU  - B. P. Kay
AU  - L. Morrison
AU  - C. Mueller-Gatermann
AU  - C. O'Shea
AU  - P. H. Regan
AU  - W. Reviol
AU  - D. M. Rhodes
AU  - R. Russell
AU  - N. Sensharma
AU  - D. Seweryniak
AU  - M. Siciliano
AU  - R. S. Sidhu
AU  - I. A. Tolstukhin
AU  - C. Y. Wu
PY  - 2026
DA  - 2026/10/20
PB  - arXiv
DO  - 10.48550/arxiv.2610.28202
UR  - https://arxiv.org/abs/2610.28202
AB  - Stable isotopes of mercury, with two fewer protons than magic lead, are found experimentally to exhibit oblate deformation, similar to neighbouring platinum isotopes. These isotopes are of special interest due to the use of ^199Hg as an experimental laboratory for electric dipole moment searches, which are a powerful test of charge-parity (CP) violation and the interpretation of which depends critically on the quadrupole and octopule shapes of the underlying nucleus. It is observed that the ratio between experimental quadrupole moments and electric quadrupole transition strengths exceed physical limits, placing uncertainty on this underlying shape. In an effort to resolve this situation, a Coulomb excitation experiment was performed to remeasure the spectroscopic quadrupole moment (Q_s(2^+_1)) of ^200Hg and ^202Hg utilising ^48Ti and ^120Sn targets. The values obtained were Q_s(2^+_1) ^200,202Hg = 0.52(14), 0.63(10) eb, lying within physical limits defined by B(E2) values but still consistent with near axially-symmetric oblate deformation. A systematic study of nuclei indicates that, as with neighbouring Pt isotopes, ^200,202Hg are strongly oblate deformed, albeit without fully developing into an axial rotor.
ER  -

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