Extended interacting boson model with configuration mixing description for Mo98

An extended version of the interacting boson model (IBM), encompassing two-particle--two-hole (2p-2h) excitations originating from below a valence shell and one-particle--one-hole (1p-1h) excitations extending to the upper next-nearest major shell, is developed to investigate cross-shell excitation effects in the transitional nucleus ⁹⁸Mo. This extended IBM framework is utilized to reproduce experimentally observed properties such as low-lying positive-parity level energies, $B(E2)$ values, and the electric quadrupole moment of the 2₁⁺ state, ρ²(E0,0₂⁺→0g⁺), as well as the strength functions of the isoscalar giant monopole resonance (ISGMR) and the isoscalar giant quadrupole resonance (ISGQR) in ⁹⁸Mo. It is shown that the extended consistent-Q IBM, incorporating configuration mixing of both 2p-2h excitations from below the valence shell and 1p-1h excitations to the upper next-nearest major shell, describes the low-lying structural properties and the ISGMR and ISGQR strength distributions of ⁹⁸Mo quite well, with the ISGMR and the ISGQR strength distributions comparable to the results of the self-consistent quasiparticle random-phase approximation with Skyrme interactions.