[en] The light krypton isotopes show two minima in their potential energy corresponding to elongated (prolate) and compressed (oblate) quadrupole deformation. Both configuration are almost equally bound and occur within an energy range of less than 1 MeV. Such phenomenon is called shape coexistence. An inversion of the ground state deformation from prolate in Kr⁷⁸ to oblate in Kr⁷² with strong mixing of the configurations in Kr⁷⁴ and Kr⁷⁶ was proposed based on the systematic of isotopic chain. Coulomb excitation experiments are sensitive to the quadrupole moment. Coulomb excitation experiments of radioactive Kr⁷⁴ and Kr⁷⁶ beam were performed at GANIL using the SPIRAL facility and the EXOGAM spectrometer. The analysis of these experiments resulted in a complete description of the transition strength and quadrupole moments of the low-lying states. They establish the prolate character of the ground state and an oblate excited state. A complementary lifetime measurement using a 'plunger' device was also performed. Transition strength in neighboring nuclei were measured using the technique of intermediate energy Coulomb excitation at GANIL. The results on the Se⁶⁸ nucleus show a sharp change in structure with respects to heavier neighboring nuclei. (author)