This is a different process than the more random nuclear disintegration that precedes light fragment emission in ternary fission, which may be a result of a nuclear reaction, but can also be a type of spontaneous radioactive decay in certain nuclides, demonstrating that input energy is not necessarily needed for fission, which remains a fundamentally different process mechanistically.
In the absence of any energy loss for fragment deformation and excitation, as in cold fission phenomena or in alpha decay, the total kinetic energy is equal to the Q-value and is divided between the particles in inverse proportion with their masses, as required by conservation of linear momentum where Ad is the mass number of the daughter, Ad = A − Ae.
[7] Four theoretical approaches were used: fragmentation theory by solving a Schrödinger equation with mass asymmetry as a variable to obtain the mass distributions of fragments; penetrability calculations similar to those used in traditional theory of alpha decay, and superasymmetric fission models, numerical (NuSAF) and analytical (ASAF).
[14] The first experimental report was published in 1984, when physicists at Oxford University discovered that 223Ra emits one 14C nucleus among every billion (109) decays by alpha emission.
In alpha-like theories S is an overlap integral of the wave function of the three partners (parent, daughter, and emitted cluster).
A very large number, of the order 105, of parent-emitted cluster combinations were considered in a systematic search for new decay modes.
The large amount of computations could be performed in a reasonable time by using the ASAF model developed by Dorin N Poenaru, Walter Greiner, et al.
Comprehensive tables of half-lives, branching ratios, and kinetic energies have been published, e.g.[17][18] Potential barrier shapes similar to that considered within the ASAF model have been calculated by using the macroscopic-microscopic method.
One can obtain with good approximation one universal curve (UNIV) for any kind of cluster decay mode with a mass number Ae, including alpha decay In a logarithmic scale the equation log T = f(log Ps) represents a single straight line which can be conveniently used to estimate the half-life.
[21] The experimental data on cluster decay in three groups of even-even, even-odd, and odd-even parent nuclei are reproduced with comparable accuracy by both types of universal curves, fission-like UNIV and UDL[22] derived using alpha-like R-matrix theory.
In order to find the released energy one can use the compilation of measured masses[23] M, Md, and Me of the parent, daughter, and emitted nuclei, c is the light velocity.
The main experimental difficulty in observing cluster decay comes from the need to identify a few rare events against a background of alpha particles.
The quantities experimentally determined are the partial half life, Tc, and the kinetic energy of the emitted cluster Ek.
Using a semiconductor telescope and conventional electronics to identify the 14C ions, the Rose and Jones's experiment was running for about six months in order to get 11 useful events.
With modern magnetic spectrometers (SOLENO and Enge-split pole), at Orsay and Argonne National Laboratory (see ch.
A key role in experiments on cluster decay modes performed in Berkeley, Orsay, Dubna, and Milano was played by P. Buford Price, Eid Hourany, Michel Hussonnois, Svetlana Tretyakova, A.
A strong shell effect can be seen: as a rule the shortest value of the half-life is obtained when the daughter nucleus has a magic number of neutrons (Nd = 126) and/or protons (Zd = 82).