| Summary: | Based on the well-known rotor-vibrator model and the particle-plus-rotor model, multi-particle-hole excitations from a collective even-even core described by the rotor-vibrator is considered to describe well-deformed even-even nuclei. Like the particle-plus-rotor model, the intrinsic Vierergruppe (D<sub>2</sub>) symmetry is still preserved in the rotor-vibrator plus multi-particle-hole description. It is shown that a series of experimentally observed 0<sup>+</sup> states in these nuclei may be interpreted as the multi-particle-hole excitations in a complementary manner to the beta and gamma vibrations described by the rotor-vibrator model. As a typical example of the model application, low-lying positive parity level energies below 1.990 MeV in the eight experimentally identified positive parity bands; a series of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mn>0</mn><mo>+</mo></msup></semantics></math></inline-formula> excitation energies up to <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msubsup><mn>0</mn><mn>16</mn><mo>+</mo></msubsup></semantics></math></inline-formula>; and some experimentally known B(E2) values, E2 branching ratios, and E2/M1 and E0/E2 mixing ratios of <sup>154</sup>Gd are fitted and compared to the experimental data. The results suggest that the multi-particle-hole-pair configuration mixing may play a role in these 0<sup>+</sup> states.
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