Nuclear Data Section
International Atomic Energy Agency
P.O.Box 100, A-1400 Vienna, Austria
Memo CP-D/646
Date:
To:
From:
Subject:

10 June 2010
Distribution
V. McLane, N. Otsuka, O. Schwerer, S. Dunaeva
Reaction products that are unstable against prompt particle decay
Proposal for new branch code ISP

At the 2010 NRDC meeting, a conclusion was reached that intermediate nuclides thatare unstable against prompt particle decay will be coded in SF4 when the states areexclusively identified by the experiment. The purpose of this memo is to define therules for when the unstable nuclide is coded vs. when the break-up particles should becoded.

Proposed branch code ISP
As part of this exercise, we saw the need for a new branch code. We propose theaddition of the following code to Dictionary 30:
Partial with respect to a level in an intermediate nucleus that is notcoded in SF4.

ISP

This code may be used in combination with PAR when levels are given for both theintermediate nucleus and the final nucleus.
Example:Be(10C,x)10C* → p + 9B g.s. → 2p + 2α

9REACTION…
EN-SEC(4-BE-9(6-C-10,P+X)5-B-9,ISP/PAR,SIG)(E-LVL1,5-B-9)(E-LVL2,6-C-10)

General rule for compilation of reaction products: When a reaction proceeds
through an intermediate nucleus that is unstable and breaks up with the emission ofparticles (e.g. n, p, α), the reaction is coded with the products of the breakup as theoutput particles.
Example: The cross section for 9Be(n,2n 2α) is compiled as:
REACTION(4-BE-9(N,2N+A)2-HE-4,,SIG)

Reaction products that are unstable against prompt particle decay
The ground states of the following nuclides have been identified as unstable:• 5He → n + d• 5Li → p + α• 6Be → 2p + α• 8Be → 2α
• 9B → p + 2α
Also, some nuclides have a particle decay threshold
Example: 6-C-12 → 3 α; threshold E x = 7.65 MeV
Therefore, an exception is made to the above general rule for only those cases where
the reaction is not a function of the final product and when one or both of thefollowing is true:•The reaction is a function of the unstable product, e.g., proceeds through a given
excited state of the unstable product.

•The unstable product is identified unambiguously, and the data given is for only
the reaction that proceeds through that reaction channel, e.g., where the unstableproduct is measured with a track detector.

In the above cases, the intermediate nucleus is coded in SF4. The branch code PAR isused to specify the level of the intermediate nucleus. The definition of the nucleus
using the BIB keyword EN-SEC is optional.
Example:Be(n,2n)8Be(g.s.) → 2α

9REACTION(4-BE-9(N,2N)4-BE-8,PAR,SIG)

However, if the reaction is a function of one or more of the final products it must be
coded with the final products in SF3 and SF4. In this case, if the reaction is also afunction of a level the intermediate nucleus, the intermediate state is specified using
the branch code ISP. The intermediate nucleus must be given under the BIB keyword
EN-SEC.
Example:C(14N,d)24Mg* → α + 20Ne(g.s.)

12

REACTION…
EN-SEC(6-C-12(7-N-14,D+A)10-NE-20,ISP/PAR,……
(E-LVL1,12-MG-24)(E-LVL2,10-NE-20)

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

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