Fission lifetimes of Th nuclei measured by crystal blocking

Crystal Blocking Measurements of the Time Delay of Fission Induced byS32,Ti48, andAndersen1, Chevallier2, Forster3 et al. 2007Phys. Rev. Lett.Self Cite

“…Earlier, we reported measurements with 170 -180 MeV 32 S beams (performed at the tandem accelerator at the University of München, Garching), which apparently showed no lifetime effects [16]. Here we extend the measurements to 48 Ti and 58 Ni beams.…”

“…The measured dips are clearly narrower, and this is interpreted as an effect of a displacement of the nucleus before fission. The reason for the different conclusion in [16] for S induced fission is the comparison there of the fission dip with the elastic dip recorded at the same bombarding energy. As illustrated in Fig.…”

“…The measured time delays cannot be explained within the Bohr-Wheeler model with multichance fission and a broad time distribution [13][14][15][16]21]. Instead, the observations support a picture of highly damped deformation change, from the initial touching of two spheres to a more symmetric, elongated shape at scission, with simultaneous cooling by neutron emission without much influence on the dynamics [10].…”

“…Thin (100) Elastically scattered ions and reaction products were measured in a position-sensitive gas ionization counter at 54.3 to the beam direction and 48.3 cm from the target. The detector was identical to the one used earlier [16] except that CF 4 was used as the counter gas instead of isobutane. The anode was split into E (12 cm long) and E rest (18 cm long) electrodes, which provided particle identification.…”

“…A small deviation from the scaling with 1 might be expected due to screening by projectile electrons, but our measured dips for elastic scattering of S, Ti, Ni, and Ge show no indication of such a deviation. The position data were corrected on the basis of data taken with a mask placed in front of the detector [16]. These data also provided for an angular calibration of the detector.…”