Isomeric states in light even Pb isotopes

Searches for isomers in the μsec range for isotopes ¹⁹⁴⁻²⁰⁰Pb revealed a new lifetime of T_1/2=10 μsec for the 1541-keV state in ¹⁹⁴Pb and confirmed the T_1/2=0.5-μsec and T_1/2=4-μsec half-lives for the 9⁻ states in ²⁰⁰Pb and ¹⁹⁸Pb, respectively. No lifetime in the μsec range was found in ¹⁹⁶Pb indicating that the 688.9-keV transition is not of E3 character as proposed before by Chojnacki et al. Lifetimes of T_1/2=134±20 nsec and T_1/2=61±14 nsec for the 5⁻ and 9⁻ states in ¹⁹⁶Pb were derived from a γ-γ-t coincidence experiment. A possible distortion of the time spectra obtained in in-beam experiments is discussed. Experimental B(E2) and B(E3) values are compared with single-particle estimates for some possible two-neutron configurations of the states involved.