De-excitation of compound nuclei with A around 56: reduction of the emission barriers for protons and alpha particles
P. Jänker - H. Leitz - K.E.G. Löbner - M. Moralles - H.G. Thies
Sektion Physik, University of Munich, D-85748 Garching, Germany
Received: 15 June 1998 / Revised version: 5 November 1998 Communicated by C. Signorini
Abstract
This paper contributes to the discussion on the phenomena of the enhanced emission
of low-energetic charged particles during compound nuclei decay. The decay of compound
nuclei 52Fe, 56Ni, and 59Cu was studied. Energy spectra and emission angles of
evaporated charged particles were measured in coincidence with gamma rays to determine the
corresponding evaporation residue nucleus. Additionally, evaporation residue distributions
were determined with the Munich rf recoil spectrometer. In this way, detailed
channel-specific evaporation data were obtained for theoretical analysis. We extracted
evaporation barriers and compared them with corresponding fusion barriers. The main result
was revealed to be a lowering of the evaporation barrier for protons and alpha particles
relative to the fusion barriers. But the observed effect is not as intensive as reported
in recent studies.
PACS
24.10.-i Nuclear-reaction models and methods -
25.60.Pj Fusion reactions -
25.70.Gh Compound nucleus
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