β+/electron-capture decay of192,194,196,198,200Bi: Experimental evidence for low lying0+states

Levels in the ${}_{}{}^{192}{}_{}{}^{}$,194,196,198,200Pb isotopes were studied via the ${\beta }^{+}$/electron-capture decay of mass separated Bi isotopes. Multiscaled spectra of γ rays, x rays, and conversion electrons, and γ-γ and γ-${\mathrm{e}}^{\mathrm{-}}$ coincidences were measured. The existence of $0^{+}$ states in the ${}_{}{}^{192\mathrm{-}200}{}_{}{}^{}\mathrm{Pb}$ nuclei is shown and evidence for the beginning of a collective band built on top of the $0_2^{+}$ states is seen in ${}_{}{}^{192}{}_{}{}^{}$,194,196Pb. A discussion in terms of characteristic properties of intruder states in the even-even nuclei and in terms of a one-broken-neutron-pair formalism is given. This shows clearly the presence of both neutron and proton [π(2p-2h)] based states in the semimagic Pb nuclei at low excitation energy.