Duan, H. R.Jia, H. M.Lin, C. J.Hinde, D. J.Banerjee, K.Buete, J.Carter, I. P.Cook, K. J.Dasgupta, M.Sengupta, C.Swinton-Bland, B. M.A.Williams, E.Wang, D. X.Gu, F. C.Yang, L.Ma, N. R.Wen, P. W.Yang, F.Luo, T. P.Zhang, H. Q.2026-07-032026-07-032469-9985ORCID:/0000-0002-7895-458X/work/219172545ORCID:/0000-0001-8755-2411/work/219176470ORCID:/0000-0002-4595-0742/work/219176557ORCID:/0000-0002-5911-1333/work/219178678ORCID:/0000-0002-1677-9421/work/221768086https://hdl.handle.net/1885/733812490The observation of mass-asymmetric fission in the neutron-deficient sublead region has dramatically expanded the region of mass-asymmetric fission in the nuclide chart, and has led to intense experimental and theoretical investigations. The mechanism for this asymmetric fission mode in this mass region is still not fully understood. To investigate the systematic evolution of the mass-asymmetric fission modes with increasing excitation energy and varying neutron numbers of the neutron-deficient nuclei, the fission-fragment mass distributions have been measured in fissions of the excited compound nuclei Pt176,186 formed by fusion of S32+Sm144,154 over a wide excitation energy range. The fission-fragment mass distributions of Pt176,186 can be described by two main fission modes at all the measured energies, that is one mass-symmetric and one mass-asymmetric fission based on triple-Gaussian fits. In addition, the gef model was used to provide a general prediction for the present paper. The available experimental systematics for the fission of neutron-deficient Pt isotopes suggests that the proton shell of the fragments dominates the mass-asymmetric fission mode, with the most probable proton number being ZL≈35 for the light fragments and ZH≈43 for the heavy ones.We thank the anonymous referee for the fruitful suggestions to improve the paper. This work is supported by the National Key Research and Development Program of China (Grants No. 2023YFA1606402 and No. 2022YFA1602302), the National Natural Science Foundation of China (Grants No. U2167204, No. 12175314, No. 12275360, and No. 12235020), the Continuous Basic Scientific Research Project, and the Australian Research Council through Discovery Grants No. DP190100256, No. DP190101442, No. DP200100601, No. DP230101028, and No. DE230100197. Support for operation of the Heavy Ion Accelerator Facility from the Australian National Collaborative Research Infrastructure Strategy through the HIA project is acknowledged. We also thank M. A. Stoyer for his contribution towards running the experiment.9en© 2025 American Physical Society.202510.1103/PhysRevC.111.044613105003940181