Shape coexistence offers one of the most demanding tests of modern nuclear theories. However, firmly establishing it experimentally requires an exhaustive knowledge of a large number of nuclear properties related to the nuclear deformation. The thesis focuses on the manifestations of the shape-coexistence in atomic nuclei with mass number A ≈ 100, specifically ¹⁰⁶Cd and ¹⁰⁰Zr.

The properties of ¹⁰⁶Cd were studied via “unsafe” Coulomb excitation using the AGATA + VAMOS setup at GANIL, France. The measured excitation cross-sections were analyzed with the help of coupled-channel codes GOSIA and FRESCO. The deduced transition probabilities were compared to results of previous “safe” Coulomb-excitation studies and lifetime measurements, demonstrating that nuclear structure information can be reliably obtained from “unsafe” Coulomb-excitation data. Shape coexistence in ¹⁰⁶Cd is discussed in the context of Beyond-Mean-Field calculations. In addition, information on E3 transition strengths to several negative-parity states in ¹⁰⁶Cd is reported for the first time.

The second half of my PhD work is based on a beta-decay study of ¹⁰⁰Zr performed with the GRIFFIN spectrometer at TRIUMF, Canada. The level scheme of ¹⁰⁰Zr has been extended, and branching and mixing ratios were extracted for multiple transitions. Using gamma-gamma angular correlations, several new low-energy excited 0⁺ states were identified, as well as a candidate for the 2⁺ state built on the newly assigned fourth 0⁺ state. The results are discussed in the framework of recent Monte-Carlo Shell-Model calculations, which predict multiple-shape coexistence.