$\gamma $-rays from the decay of the 0.26 s isomer in $^{254}$No*

The t$_{1/2}$=0.26 s, high-K isomer in $^{254}$No, first identified by Ghiorso et al. and further studied by Mukherjee et al. through the detection of electrons, was populated using the $^{208}$Pb($^{48}$Ca,2n) reaction at a beam energy of 219 MeV, provided by the ATLAS accelerator at Argonne. The evaporation residues were transported through the Fragment Mass Analyzer (FMA), identified by mass and then implanted in a 40x40 mm Double-Sided Silicon Strip Detector (DSSD). Conversion electrons following the de-excitation of the isomer and $\alpha $-particles from $^{254}$No were detected, with the requirement that all signals originate from the same DSSD pixel. The $\gamma $-rays from the decay of the isomer were detected using three Ge clover detectors placed around the DSSD. The inferred decay pattern of the isomer, based on the observed $\gamma $-rays, including two high-energy transitions observed in earlier prompt studies, indicate that the isomer decays to an excited two-quasiparticle or octupole vibrational band.\\ *Supp. by USDOE Grant DE-FG02-94ER40848 and W-31-109-ENG-38.