Nuclear Structure and Shape Dynamics of 194Po in the Framework of IBM-1 and VMI-Based Models

The structural properties of the even–even nucleus 194Po have been investigated using the Interacting Boson Model (IBM-1), the Variable Moment of Inertia (VMI) model, and its generalized extension (GVMI). Available experimental level energies were used as input data, and additional observables—excitation energies, energy ratios, reduced electric transition probabilities B(E2), and electric quadrupole moments ( $${{Q}_{l}}$$ )—were calculated with the IBMT.FOR code. The IBM-1 Hamiltonian was diagonalized for N = 9 bosons, with effective charges fitted via the B(E2).dat input scheme. The results show that IBM-1 reproduces the low-spin spectrum and transition rates well, while VMI and GVMI better capture the upward curvature of the ground band at higher spin. The experimental energy ratios (R4/2 = 2.15, R6/2 = 3.59, R8/2 = 3.66) lie close to the SU(5) vibrational limit and far from the SU(3) rotor, placing 194Po on the SU(5)–O(6) side of the Casten triangle. The B(E2) data are reproduced within ~20%, while the model predicts a distinctive rise–collapse–recovery pattern at higher spin due to SU(5)–O(6) interference. For the reduced transition probability, the experimental value of B(E2; $$~2_{1}^{ + }$$ → $$~0_{1}^{ + }$$ ) was 0.2225 e2b2, while the theoretical calculation yielded a value of 0.18 e2b2. The calculated quadrupole moments Q of the five 2+ states exhibit alternating signs, consistent with γ softness and strong state mixing. It was found that the experimental value of Q is 5.5 eb, which is in excellent agreement with the theoretical prediction of 5.5 eb. For 194Po, the ground-state and γ-bands were analyzed using IBM-1, VMI, and GVMI models, enabling the prediction of levels not yet experimentally confirmed. Several tentative experimental values were supported by the models, with VMI and GVMI showing the closest agreement (χ2 = 0.000091 and 0.000001, respectively). The IBM-1 framework, supported by VMI/GVMI trends, provides a reliable description of its structure, while the predicted high-spin B(E2) transitions and quadrupole moments remain decisive tests for future experiments.