ADOPTED LEVELS for ¹³Be

Authors: J.H. Kelley, C.G. Sheu and J. E. Purcell  Citation: Nucl. Data Sheets 198, 1 (2024)  Cutoff date: 1-Aug-2024

Full ENSDF file

Q(β-)=17037 keV 10	S(n)= -450 keV 10	S(p)= 22700 keV 30	Q(α)= -9770 keV 50

References:
A	1H(14Be,13Be):1	B	1H(14Be,13Be):2
C	1H(14B,13Be)	D	2H(12Be,p)
E	2H(12Be,13Be)	F	9Be(13B,13Be)
G	9Be(18O,13Be)	H	9Be(48Ca,X)
I	C(14Be,13Be)	J	C(14B,13Be)
K	13C(π-,π+)	L	13C(14C,14O)
M	14C(π-,p)	N	14C(π-,PD)
O	14C(7Li,8B)	P	14C(11B,12N)
Q	U(p,X),232Th(15N,X)

E(level) (keV)	XREF	Jπ(level)	T1/2(level)
0	AB  E    J      Q	1/2-	0.43 20  % n = 100
0.39E3 3	A C EF   J  M  P	1/2+	1.78 MeV 16  % n = 100
1.61E3 3	ABCDEFGHIJKLM OP	5/2+	0.40 MeV +4-5  % n = 100
2.53E3 4	A C  F  IJ  M  P	(5/2+)	≈ 0.4 MeV % n = 100
≈3.55E3	C	(3/2+)	≈ 0.4 MeV % n = 100
4.63E3 5	AB D F     LM  P	(3/2-,5/2+)	1.4 MeV 2  % n = 100
5.43E3 10	B             P		% n = 100
6.55E3	D
8.1E3 2	F     L   P		0.9 MeV 3
9.6E3	D
18.7E3	K		9.0 MeV 15
≈30E3	N
E(level): The ground state is taken as Ec.m.(n+12Beg.s.)=0.45 MeV 1. E(level): Broad states are reported at Ec.m.(12Beg.s.+n)=2.56 MeV and 2.35 MeV in 9Be(13B,13Be) and C(14B,13Be), respectively. The present evaluation assumes these correspond to a combination of unresolved groups at Ec.m.(12Beg.s.+n)=2.0 MeV and 2.98 MeV. T1/2(level): LABEL=Γ

Additional Level data and comments:

E(level)	Comments
0	From Eres=0.46 MeV 1 (see fit to (2010Ko17) 1H(14Be,13Be) given in (2013Ak02)), 0.44 MeV 1 (2013Ak02) 1H(14Be,13Be) and 0.40 MeV 3 (2014Ra07) C(14B,13Be). Also see Eres=0.51 MeV 1 initially reported in (2010Ko17). E(level): Jπ(level): From (2010Ko17) whose analysis of the n+12Be momentum distribution and the resonance width indicate an inversion of the 1s1/2 and 0p1/2 shells. The inversion is further supported from analysis of the low-lying 14Be level structures (1999La20). (2007Bl02, 2018Ri05,2019Fo02) discuss the expectation for a Jπ=1/2- state to be populated in neutron stripping from 14Be and to be absent in proton stripping from 14B; hence Jπ=1/2- is recommended for this resonance. T1/2(level): From unweighted average of Γ=0.11 MeV 2 (see fit to (2010Ko17) given in (2013Ak02)), 0.39 MeV 5 (2013Ak02) and 0.80 MeV 20 (2014Ra07).
0.39E3	XREF: α(0.36×103)M(0.20×103). E(level): Decays via 12Beg.s.+n. Jπ(level): From (2015Ma62) 9Be(13B,13Be) where the 12Be+n resonance is s-wave in character, see additional discussion in (2013Ak02, 2019Fo02). T1/2(level): From Γ=2.1 MeV 3 (see fit to (2010Ko17) given in (2013Ak02)) and Γ=1.70 MeV 15 (2018Ri05). See other value Γ=0.30 MeV 30 in (2014Ra07).
1.61E3	XREF: α(1.50×103)B(1.9×103)J(1.90×103)K(2.0×103)M(1.42×103). E(level): Decays via 12Beg.s.+n [Eres=2.11] and 12Be*(2.109)+n [Eres<0.1 MeV] (2013Ak02,2018Ri05,2019Co12). Jπ(level): From (2013Ak02) 1H(14Be,13Be) where d-wave decay is reported in 12Beg.s.+n and s-wave character is reported in 12Be(2+)+n decay. In (1998Be28) the 12C(11B,12N) and 14C(11B,12N) spectra are shown to be similar, which supports 5/2+ for this state. T1/2(level): From (2023Ko21). See also 0.3 MeV 1 in (1998Go30), 0.3 MeV 2 in (1992Os04), ≈0.5 MeV in (2013Ak02), ≈0.4 MeV in (2018Ri05) and ≈0.3 MeV in (2007Si24).
2.53E3	XREF: C(2.47×103)J(1.90×103). E(level): From Eres=2.98 MeV 4 (2010Ko17 in 2013Ak02) 1H(14Be,13Be), 3.02 MeV 9 (2013Ak02) 1H(14Be,13Be), 2.90 MeV 13 (1998Be28) 14C(11B,12N). Decays via 12Beg.s.+n (2013Ak02,2018Ri05); an unobserved branch via 12Be(02+)+n is expected. Jπ(level): From (2018Ri05) 1H(14B,13Be). The state’s population in proton knockout, where negative parity states are suppressed, supports a positive parity assignment. The state is thought to decay most strongly to 12Be(02+), but this branch is difficult to observe; see discussion in (2019Fo02). T1/2(level): From ≈0.5 MeV (2010Ko17, 2013Ak02), ≈0.4 MeV (2007Si24) and |<0.15 MeV (1998Go30).
3.55E3	E(level): Decays via 12Beg.s.+n [Eres=4.0] and 12Be*(2109)+n [Eres≈2.1 MeV]. Jπ(level): Populated in proton knockout from 14B indicating π=+; see further discussion in (2019Fo02) indicating a Jπ=3/2+ state is expected in this vicinity with similar decay properties.
4.63E3	XREF: α(4.75×103)M(4.51×103)p(4.49×103). E(level): From Eres=5.2 MeV 1 (2010Ko17 in 2013Ak02) 1H(14Be,13Be), 5.1 MeV 13 (2019Co12) 1H(14Be,13Be), 5.13 MeV 7 (1992Os04) 13C(14C,14O), 4.96 MeV 20 (1998Go30) 14C(π-,p) and 4.94 MeV 8 (1998Be28) 14C(11B,12N). (2013Ak02) report the state decays to 12Be*(2.71 MeV) while (2019Co12) report the state decays to 12Be*(2.1 MeV). Jπ(level): From (2013Ak02) 1H(14Be,13Be) where s-wave neutron emission from a 3/2- state (or p-wave emission from a 5/2+ state) to 12Be(1-) are preferred. T1/2(level): From (2010Ko17 in 2013Ak02). Others are 0.4 MeV 2 (1992Os04) and ≈1.7 MeV (1998Go30).
5.43E3	E(level): From (1998Be28) 14C(11B,12N); see also Eres=5.7 MeV 14 in (2019Co12) 1H(14Be,13Be). Decays to 12Be*(2.71 MeV)+n (2019Co12).
6.55E3	E(level): From (1995Ko10, 1995Ko27) 2H(12Be,p). Decay mode not reported; likely mode is %n=100.
8.1E3	XREF: p(7.5×103). E(level): Decay mode not reported; likely mode is %n=100.
9.6E3	E(level): From (1995Ko10, 1995Ko27) 2H(12Be,p). Decay mode not reported; likely mode is %n=100.
18.7E3	E(level): Decay mode not reported; likely mode is %n=100.
30E3	E(level): From (2016Ko22) 14C(π-,pd). Decay mode not reported; likely mode is %n=100.

General Comments:

See shell model analyses in: 1983Va31,1984Va06,1985Po10, 1987Sa15, 1992Go17, 1996Wa35, 2007Gu03

See Mean Field model analyses in: 1996Su24, 1997Ba23, 1997Ba54, 1997Re07, 2005Ar12, 2006Sh20, 2020Al27

See Cluster Model and AMD analyses in: 1981Se06, 1994De32, 1995De31, 2005Ne03, 2005Th06, 2012Ka10, 2013Ma53, 2021Co07

See other analyses in: 1995Ta32, 1999Ka67, 2000Bh07, 2004De60, 2004La24, 2004Ne16, 2004Sa50, 2006Ko02, 2007Bl02

See discussion on low-lying 13Be levels and possible level inversion in: 1985Po10, 1995De31, 1997Re07, 1999La20, 2004Ta03, 2008Ha16, 2009BlZZ, 2010Bl12, 2012Bo15, 2012Fo22, 2013Fo03, 2014Fo21, 2014Ho08, 2015Fo06, 2018Fo07, 2019Fo02.

In the present analysis the data are somewhat discrepant. The experimental approaches often provide incomplete measurements of the reaction observables and result in what appear as incompatible observations. The 14C(11B,12N) and 14C(π-,p) results have been used to guide an initial level scheme since these results are insensitive to ambiguities present in level energy determination based on n+12Be momentum reconstruction. The modern results where n+12Be kinematics are measured provide meritous information on levels energies and decay modes and have been heavily consulted.

In surveying the results a trend appears where two groups around Erel( n+12Be)≈0.5-0.7 MeV and 2.3-2.5 MeV can reasonably fit the energy spectrum. However in studies utilizing γ+n+12Be coincidence events, where 12Be excited states are considered, evidence is found for a larger number of neutron groups corresponding to levels at Eres(n+12Beg.s.)≈0.4, 0.8, 2.0 and 3.0 MeV. The importance of including γ emission in analyzing the n+12Be spectra is highlighted below with comments on two mesurements. First, in (2001Th01) the 9Be(18O,13Be|)12Be+n) reaction was measured; evidence for two components, at Eres≈0 and 2.0 MeV, was found in the relative energy spectrum; however subsequent understanding supports the interpretation that these groups are connected to a Eres(n+12Be)≈2 MeV level that decays to 12Beg.s. with En≈2 MeV and also decays to the high energy tail of 12Be*(2.1 MeV) . Second, in the initial analysis of the 1H(14Be,13Be|)12Be+n) resonance spectrum of (2010Ko17), resonances at Eres=0.51 MeV 1 with Γ=0.45 MeV 3 and Eres=2.39 MeV 5 with Γ=2.4 MeV 2 were found, but the discussion indicated the Eres=2.39 MeV region could also be reproduced with groups at Eres=2.0 MeV and Eres=2.9 MeV as suggested by (1992Os04,1998Be28). α reanalysis of (2010Ko17) in (2013Ak02) found evidence for 5 levels that decay to 12Be ground and excited states.

Lastly, the virtual play-by-play analysis of experimental results given in the discussion of Fortune’s (2012-2019) articles provides insight into the evolution of our understanding of this nucleus. In these articles, extensive discussion on experimental work is given along-side a simple potential model analysis. Early on, the statement is made that, "The (lowest) s state in 13Be is unbound, and unbound neutron s states are notoriously hard to handle. " Throughout the series of articles, listed above, the discussion focuses on likely structure configurations, the order of low-lying level spins and reasonable widths, and decay modes that can reasonably explain the data. See related discussion in (2021Co07).

Q-value: S2n=2720 keV 10.