EFFECT OF ROTATION OF FISSIONING NUCLEI IN THE ANGULAR DIS- TRIBUTIONS OF PROMPT NEUTRONS AND γ -RAYS IN FISSION OF 235U IN 0.3 RESONANCE AT THE HOT SOURCE OF POLARIZED NEUTRONS

Abstract

T-odd angular correlations in ternary nuclear fission (TRI and ROT asymme-
tries) were studied with the aim of finding a violation of Time Reversal Invariance (TRI) in
neutron-nuclear interactions. A nonzero T-odd effect was discovered in an experiment to meas-
ure asymmetry in the emission of light charged particles in the 233U ternary fission (TRI effect),
which was performed at a high-flux ILL nuclear reactor in Grenoble by the collaboration of
Russian and European institutions. As it turned out, the effect is not associated with violation of
T-invariance, but can be explained by a complex mechanism of the fission process. Later, the
ROT effect was observed in the emission of prompt gamma-rays and neutrons in fission of 235U
and 233U, although its magnitude was an order of magnitude smaller than in the emission of α -
particles in ternary fission. All experiments up to now were performed with cold polarized neu-
trons, which suggests a mixture of several spin states of the compound nucleus, the relative
contributions of which are not well known.
Our work presents the results of the first experiments to measure the ROT effect in the
fission of 235U by hot polarized neutrons at the POLI facility of the FRM-II reactor in Garching
with neutron energies of 0.3 eV. This energy corresponds to the position of the first isolated
resonance of 235U.