On the timescale of quasi fission and Coulomb fission

TL;DR

This paper clarifies the timescales of quasi fission and Coulomb fission in nuclear reactions, resolving discrepancies between different measurement techniques and confirming that quasi fission occurs on the zeptosecond timescale.

Contribution

It introduces a new interpretation of measured fission timescales by including Coulomb fission effects, aligning experimental results with nuclear theory.

Findings

Coulomb fission occurs when excitation energy exceeds fission barrier.

Measured times longer than 2-2.5 as are due to Coulomb fission.

Quasi fission timescale is confirmed to be of the order of zeptoseconds.

Abstract

Coulomb fission mechanism may take place if the maximum Coulomb-excitation energy transfer in a reaction exceeds the fission barrier of either the projectile or target. This condition is satisfied by all the reactions used for the earlier blocking measurements except one reaction 208 Pb + Natural Ge crystal, where the measured timescale was below the measuring limit of the blocking measurements < 1 as. Hence, inclusion of the Coulomb fission in the data analysis of the blocking experiments leads us to interpret that the measured time longer than a few attoseconds (about 2-2.5 as) is nothing but belonging to the Coulomb fission timescale and shorter than 1 as are due to the quasifission. Consequently, this finding resolves the critical discrepancies between the fission timescale measurements using the nuclear and blocking techniques. This, in turn, validates the fact that the quasifission timescale is indeed of the order of zeptoseconds in accordance with the nuclear experiments and theories. It thus provides a radical input in understanding the reaction mechanism for heavy element formation via fusion evaporation processes