Nuclear Data Section
International Atomic Energy Agency
P.O.Box 100, A-1400 Vienna, Austria
Memo CP-D/626
Date:
To:
From:

17 March 2010
Distribution
K. Hagino, K. Nishio, N. Otsuka

Subject:
Reference:

New LEXFOR entry – Fusion
Memo CP-E/110

Below is a new LEXFOR entry Fusion. This is an update of “Fusion, Fast Fission, andDeep Inelastic Scattering” in the current LEXFOR entry “Reaction mechanism”. The
definition of “evaporation residue” proposed in Memo CP-E/110 is also included inthis draft. New quantity code ,SIG,,ER is also proposed for an entry from India [1].
Dictionary 236 (Quantities),SIG,ER
Evaporation residue production cross section
Quantity,SIG,ER

Reaction TypeCSDimension
BReference[1] S. K. Hui et al., Phys. Rev. C62 (2000)054604 (EXFOR D6088)

FusionFusionFor heavy ion reactions under suitable conditions, the incident projectile canovercome or tunnel the Coulomb barrier formed between projectile and target nuclei,
and a composite system is formed. When nucleons which are contained in theinteracting nuclei are fully equilibrated in the composite system with a time longer
than those for the other reaction channel, the system reaches the condition called
compound nucleus with a certain excitation energy, and thus the system does not haveany memory in the entrance channel, it results in a compound nucleus in an excitedstate. This result is called fusion.
Evaporation residue production
A compound nucleus produced in the fusion reaction has two major de-excitation
modes, fission and particle evaporation. The final product of the de-excitation process
in which the nucleus undergoes the emission of one or several light particles (e.g.
neutron, proton, alpha, γ- and X-rays) without interruption by fission is definedas evaporation residue.

Evaporation residues are clearly separated from the elastic-like products on the E –ΔE plot. Recoil mass separators are used especially when the cross-sections are small
due to the competition against fission in order to make a clear separation from theprojectile- and target-like nuclei. Alternative methods to detect evaporation residues
are measurement of their characteristic γ-, X-rays or α decays.
REACTION coding: Process code FUS in SF3
Example:(…(8-O-16,FUS),,SIG)(…(8-O-16,FUS),,SIG,,ER)(…(8-O-16,FUS)0-NN-1,,SIG)

Fusion cross section
Evaporation residue (production) cross section
Production cross section of neutron from
evaporation of compound nucleus

Quasi-fission
The quasi-fission is defined as a process when the interacting two nuclei overcome or
penetrate the Coulomb barrier and the system exchanges larger number of nucleons
which is followed by disintegration into two fragments. The reaction time is far
shorter than the decay time of a compound nucleus. In this case, the quasi-fission
process is influenced by the entrance channel parameters such as mass asymmetry andbombarding energy between the colliding nuclei.
Do not mix up quasi-fission with fast fission which occurs when the Coulomb barrier
disappears due to fast rotation of heavy systems (e.g. actinide beam) and thecompound nucleus cannot be defined.
Because decomposition of fission into quasi-fission and fusion-fission is notstraightforward, the yields for each fissions are not separated from the measured
spectra, and therefore only the sum of both contributions is compiled with the processcode F in REACTION SF3. (See Fission).
Deep inelastic scattering (Not presently compiled)
The case where the dinucleus system may or may not be formed, and a large part of
the kinetic energy of the incident projectile is dumped into internal energy, but breaks
apart after rotation, is called deep inelastic scattering.
Quasi-elastic scattering (Not presently compiled)
The case where the overlap of two nuclei is small and a few degrees of freedom areinvolved in the reaction is called quasi-elastic scattering. Quasi-elastic includes elasticscattering, inelastic scattering leading primarily to low excitation and nuclear transfer
with small Q-value.
The reaction time decreases in the order of fusion, quasi-fission/deep inelasticscattering, quasi-elastic scattering, Coulomb excitation; although the boundaries

between these processes are not well defined. Especially, the boundary and order
between quasi-fission and deep inelastic scattering is not very clear.
Sum rule
The fusion cross section is the sum of fusion-fission cross section and evaporation
residue cross section. The fission cross section is the sum of fusion-fission crosssection plus quasi-fission cross section.
In Light system (Z target +Z projectile ≤ 90):
Fission cross section is negligible.
Intermediate system (90 ≤ Z target +Z projectile and Z target •Z projectile ≤ 1600–1800):
Quasi-fission cross section is small
Heavy system (Z target •Z projectile ≥ 1600–1800):
The evaporation residue cross section is significantly small.

Distribution:
blokhin@ippe.ru
chiba@earth.sgu.ac.jp
claes.nordborg@oecd.org
emmeric.dupont@oecd.org
ganesan@barc.gov.in
gezg@ciae.ac.cn
hongwei@ciae.ac.cn
jhchang@kaeri.re.kr
j.roberts@iaea.org
kaltchenko@kinr.kiev.ua
katakura.junichi@jaea.go.jp
kato@nucl.sci.hokudai.ac.jp
kiralyb@atomki.hu
l.vrapcenjak@iaea.org
manuel.bossant@oecd.org
manokhin@ippe.ru
mmarina@ippe.ru
mwherman@bnl.gov
nicolas.soppera@oecd.org
nklimova@kinr.kiev.ua
cc:
hagino@nucl.phys.tohoku.ac.jp
nishio.katsuhisa@jaea.go.jp

n.otsuka@iaea.org
nrdc@jcprg.org
oblozinsky@bnl.gov
ogritzay@kinr.kiev.ua
otto.schwerer@aon.at
pronyaev@ippe.ru
r.forrest@iaea.org
samaev@obninsk.ru
s.babykina@polyn.kiae.su
scyang@kaeri.re.krs.dunaeva@iaea.org
stakacs@atomki.hu
stanislav.hlavac@savba.sk
taova@expd.vniief.ru
tarkanyi@atomki.hu
varlamov@depni.sinp.msu.ru
vlasov@kinr.kiev.ua
vmclane@optonline.net
v.zerkin@iaea.org
yolee@kaeri.re.kr