Compilation and Evaluation of Experimental Data for Nuclei in Z=2-28 Region

Completed compilation and evaluation of experimental Pn and half-lives for nuclei in the Z=2-28 region, led by Balraj Singh at McMaster University. The work involved preparing lists of neutron-rich nuclides, identifying potential emitters, analyzing available experimental data for 1n, 2n, 3n, and 4n emitters, and compiling about 280 references from 1948 to 2015. The results were based on policies outlined at RCM-1 meeting, with selected values deduced using averaging procedures. Tables include recommended half-life and Pn data, and nuclides with Q-values for possible precursors.

• Compilation
• Evaluation
• Experimental Data
• Nuclei
• Balraj Singh

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1. Completed compilation and evaluation of experimental Pn and half-lives for nuclei in Z=2-28 region Balraj Singh (McMaster University, Canada) 2ndRCM meeting on Beta-delayed neutron CRP IAEA, Vienna, Austria March 23-27, 2015

2. Collaborators and tasks McMaster Univ, Canada: Michael Birch and Balraj Singh TRIUMF, Canada: Iris Dillmann NNDC, BNL, USA: Alejandro Sonzogni, Libby McCutchan, Tim Johnson CNEA, Argentina: Daniel Abriola Selection of relevant nuclides. Search and collection of literature. Compilation and evaluation. First draft of paper: M. Birch, B. Singh Checking of data tables. Systematic plots, final draft of paper: D. Abriola, I. Dillmann, T. Johnson, E. McCutchan, A. Sonzogni Need for this compilation and evaluation work was discussed and agreed upon in previous B-DN meetings.

3. Work involved (Z=2-28 region) 1. Prepare list of neutron-rich nuclides in Z=2-28 (He to Ni) region for which beta-delayed-neutron decay is allowed from energetics, and those which have been identified experimentally. We do NOT include nuclides from systematics present in NUBASE-12 or NUDAT-2.6. Nuclei decaying by direct neutron decays are NOT included. 2. Use of AME-2012 mass tables (also priv. comm. from G. Audi for some new nuclides not in AME-12), ENSDF and XUNDL databases, NUBASE-12, NUDAT-2.6, NSR bibliographic database, research articles in journals and elsewhere, scan current literature almost daily.

4. Work involved (Z=2-28 region) 3. Potential -n emitters: 219 (1n emitters), 137 (2n emitters), 81 (3n emitters), 39 (4n emitters). Note that all 4-n emitters are also 3-n, 2-n and 1-n emitters; 3-n are 2-n and 1-n; 2-n are 1-n emitters. Visual displays will be shown later today by Stephanie Ciccone. 4. Experimental data available: 1n-emitters: 87 + 20 with upper/lower limits. 2n-emitters: 15 +5 with limits. 3n emitters: 2 +3 with limits. 4n-emitters: 1 possible case (17B, 0.4(3)% in 1988Du09. 2013Ue01: no seen in 13C ?). For ~50 nuclides there is only one P1n measurement available. For another ~40, data from one reference adopted

5. Work completed Compiled Pn and half-life data, the latter even if no Pn data available: total of about 280 references from 1948 to 2015. Based on policies and guidelines outlined at RCM-1 meeting, evaluated (or recommended) values were deduced by selecting data and using averaging procedures, when necessary. Commentary is provided in a supplementary file, which will archived, but NOT published.

6. Tables and Data Files a. Table of recommended half-life and Pn data file with complete bibliography (list of references hyperlinked to NSR database) b. Table of nuclides and Q-values for possible P1n, P2n, P3n precursors (based on AME-12) c. Table of compiled data for P1n, P2n, P3n and half-lives with all available references, including some secondary publications. d. Supplementary Table of comments for Pn and half-life measurements. (Will be made available, but not published) e. Above data exist in three .excel files (Q values for relevant nuclides, recommended Pn and half-lives, compiled data for Pn and half-lives) . These were sent to IAEA-NDS in February 2015 for setup of B-DN database

7. Paper Submitted to Nuclear Data Sheets Feb. 2015 (Currently under review)

8. Example: compiled data

9. Example: recommended data

10. Reference Standards Nuclide Half-life Pn Li-9 178.2(4) ms C-16* 754.6(80) ms N-17 4171.3(40) ms K-49* 1263(50) ms 50.7(10) 99.28(12) 95.1(7) 86(9) *Newly proposed standards. Next standard is Br-87 Discussion required later in the meeting.

11. Li-9: New result 2015Hi02: PR-C 91, 024328 (Feb 27, 2015): Expt. at TRIUMF: Pn=59.1(54)% or 61.8(54)% versus 50.7(10) adopted Question: status of this standard in view of new value? Earlier Pn results: 1981Bj01: NP-A 359, 1 (1981): 50(4)% 1981La11: NP-A 366, 449 (1981): 49.5(50)% 1992Te03: ZP-A 342, 303 (1992): 51(1)% 1995ReZZ: Proc. Conf. ENAM, Arles, p587 (1995): 50.8(2)% 2008ReZZ: P.L. Reeder: priv. comm. : 50.1(5)% Weighted average of all 6 results is still 50.7(10)%!

12. Case of K-49 as standard After N-17, current standard is Br-87 as described in the B-DN Consultants meeting in Oct 2011: INDC(NDS)-0599 (Dec 2011) Purpose: search for an appropriate standard between N-17 and Br-87 Pn results for K-49: half-life=1.263(50) s 1982Ca04: PL-B 109B, 419 (1982): 86(9)% 1983La23: PL-130B, 251 (1983): 90(14)%

13. P1n systematics (data with <25% uncertainty) E. McCutchan et al., PRC 86, 041305(R) (2012))

14. Systematics The database should have access to different approaches: Kratz-Herrmann (1978), McCutchan et al. (2012), and perhaps Miernik (2013), if it is systemetics Based on trend of Pn values for Rb-isotope shown yesterday, perhaps one should look at systematics in terms of individual Z chains, or N chains, as well as globally

15. Deficiencies found in available data Mg-34,36; Al-37,38,39; Si-38,39,40,41: Reported Pn values are preliminary (according to authors, 1998NoZW (Notani et al., Proc. Conf. ENAM, Bellaire, p359 (1998); and 1999YoZW: Yoneda et al., p78, RIKEN- 1998 report. Na-34: only total Pn=115(20) available from 1984La03 (NP-A 414, 151); Moller prediction: 34(P1n), 20 (P2n), 22(P3n) Mn-62,63,69: Pn data available from only 2000HaZL (thesis), work at ISOLDE. The results in this work are suspect since for other Mn isotopes, their values disagree significantly from published experimental values. (Their published work 1999Ha05 dealt with the decay of neutron-rich Mn isotopes, but did not refer to measurement of Pn values).

16. Example: 15B: 2000Bu33: neutron Spectrum: digitization (Digitized data files for possible inclusion in EXFOR database)

17. 9Li example: 2015Hi02: neutron spectrum. (PRC 91, 024328, Feb 27, 2015; work at TRIUMF)

18. 9Li example: 2015Hi02: neutron spectrum. TOF plot converted to neutron-energy plot

19. Coverage of Beta-delayed neutron data in ENSDF database A<21 region Prior to 2012 or so, quite a lot of delayed-neutron data, e.g. fine structure for neutron branches and gamma-ray data for A<21 was not present in ENSDF database. During 2013-2014, John Kelley from TUNL has created/updated ENSDF datasets for delayed-neutron decays of many isotopes, providing known neutron energies and gamma-ray data.

20. Z>28 region: Pn and half-life evalutation McMaster (B. Singh), TRIUMF (I. Dillmann), NNDC, BNL (A. Sonzogni, E. McCutchan, T. Johnson): A=73-110, A=137,138 (about 35 nuclides in this region have been compiled) CIAE, Beijing (X. Huang and collaborators): A=139-151 (7 nuclides compiled) VECC, Kolkata: G. Mukherjee, K. Banerjee: A=111-136 Plan is to have a joint report/publication of Z>28 region in about 2-years time.