The liquid-gas phase transition (LGPT) in heavy-ion collisions is explored using fluctuation observables within the isospin quantum molecular dynamics framework. Scaled variance $\left(\omega \right)$, skewness $\left(S\sigma \right)$, and kurtosis $\left(\kappa {\sigma }^2\right)$ of emitted protons and neutrons are analyzed over a range of beam energies. The analysis reveals a clear minimum in the scaled variance $\omega$ for both neutrons and protons, as well as a separation point between their kurtosis $\kappa {\sigma }^2$ values around 110 MeV/nucleon. Moreover, the skewness $\left(S\sigma \right)$ and kurtosis $\left(\kappa {\sigma }^2\right)$ of intermediate-mass fragments exhibit additional nontrivial fluctuation features in the same energy region. These features correlate with extrema in the energy derivatives of intermediate-mass fragment multiplicity and charge asymmetry between the largest fragment and second largest fragment $\left(a_2\right)$, providing potential indicators of LGPT under finite-size and dynamical conditions. In addition, the impact of sequential decays on the observables was checked using an afterburner sequential decay model $\left(\mathrm{GEMINI++}\right)$, and it was found that the influence on neutron and charge asymmetry $a_2$ is larger.

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• Liquid-gas phase transition
• Low & intermediate energy heavy-ion reactions
• Nuclear fragmentation
• Nuclear reactions