ENSDF: Consistency (or lack thereof) in J π assignments (including Multipolarities) Balraj Singh McMaster University, Canada IAEA-ENSDF Workshop, Vienna April 27-29, 2015

Nomenclature of J π in data record in ENSDF J π = 2+ 2(+) (2)+ (2+) (2) + (+) [2+] J1 AP 10; J2 AP 11 NOT 3 NATURAL, UNNATURAL J π = 3/2+,5/2+ 3/2,5/2 (3/2,5/2)+ 3/2(+),5/2(+) 3/2+&5/2+ (3/2+,5/2+) 3/2+(5/2+) J π =3/2+ to 9/2+ or (3/2+:9/2+) (3/2:9/2)+ ≤7/2; ≥7/2

Nomenclature of MULT in data record in ENSDF M1 (ΔJ=0,1) E2 (ΔJ=0,1,2) (M1) [E2] D Q E0 (0+ to 0+) (Implied M0) (0- to 0+) X ΔJ=0,1 transitions with or without mixing ratio δ M1+E2 or E2+M1 M1,E2 (M1+E2) (M1,E2) M1(+E2) (M1(+E2)) D+Q [M1+E2] or [M1,E2] E0+M1+E2 (for ΔJ=0 transitions)

Strong and weak rules for J π assignments (see policy document). No such document for MULT assignments (implicit in J π rules) Questions: - Any revisions needed in existing rules? - Any missing rules for certain reactions? - Any new rules needed for new physics? - How uniformly these are applied in evaluations? - Should there be standardized wording for JPI and MULT arguments in Adopted datasets?

J π / Mult assignments in Adopted and Individual decay/reaction data sets. Policy: Reaction and decay data sets items #1, 2, pages i, ii: “The J π values in decay data sets are taken from the associated Adopted Levels, Gammas data set. For reaction data sets, the J π values are from the reaction data”. Mult, δ : “The multipolarity of a γ ray and its mixing ratio given in a decay data set are from the associated Adopted γ radiation table”. No statement in policies for Mult, δ in reaction data sets? Suggestion: in reaction data set, same J π values as in paper; but MULT assignments should be based on rules. J π values in Adopted data set should be listed in comments, if different from those in reaction data set.

J π assignments for g.s. and long-lived isomers from measured magnetic-dipole moments (μ) In older rules (up to 1998 or so), agreement of measured magnetic moment with theoretical value (Schmidt limits) for a certain configuration assignment was a strong rule for J π assignment, but since then this has been moved to weak rules (#11). Some evaluations still use this as a strong rule. It perhaps can be a strong argument for nuclei very near the closed shells, but in general there is rarity of pure single-particle states. Question: how should one consider predictions from state-of-the-art large scale shell-model calculations in current literature?

J π for g.s. and long-lived isomers from systematic trends: from NUBASE or others. Varied approach in different evaluations: - Same as in NUBASE or other sources in data records - Listed as tentative (i.e. in parentheses) in data records - Listed only in comments Assignments from theoretical predictions (e.g. shell model): g.s., isomers, and higher levels

J π assignment for isobaric analog state/resonance or that of the parent state: #4 in weak rules But there are many situations where it can be a strong argument. 2007Do17: NP-A 792, 18 (2007) 32% beta feeding to 3037 level. Many such decays studied by 2007Do17 and others.

J π : isobaric analog states/resonances Observation of (very) strong peaks in particle-transfer data such as ( 3 He,p), (p, 3 He), ( 3 He,t), ( 3 He,d), etc. 44 Ca( 3 He,t) 44 Sc PRC 88, (2013) 2 nd most intense peak at 2779 keV; IAS of 44 Ca g.s. 1971INZU: priv. comm. 37 Cl( 3 He,d) 38 Ar Strong peaks at 10.63, 11.30, , MeV: IAR of 38 Cl levels

J π : current rules: silent for several reactions 2-particle transfer reactions: ( 3 He,p); (p, 3 He), and perhaps others. Note: for (p,t); (t,p); ( 3 He,n), current rule applies only for strong groups (assumed S=0 state). Many evaluations use it for weak groups as well, where S may be non-zero. Charge-exchange reactions: ( 3 He,t); (t, 3 He); (p,n), etc. Inelastic scattering experiments: (p,p’); (d,d’); (n,n’); ( 3 He, 3 He’), and perhaps other inelastic scattering experiments (in current rules only (e,e’) and (α, α’) are listed). Many evaluations use L values from (p,p’), (d,d’), etc. as strong arguments, even at high excitation energies where S can be nonzero. NRF ( γ,γ ’) experiments: dominant dipole transitions

J π assignments: mirror nuclides D. Doherty et al., PRL 108, (2012)

J π assignments: R-matrix analysis: J. Chen et al., PRC 85, (2012)

J π : new rules? Statistical analysis of gamma transitions in complex level schemes, such as in (n, γ ): DICEBOX computer code. Example: 2013Fi01.: PRC 87, (2013) E1: Standard Lorentzian model M1: Single-particle model Level density: Back-shifted Fermi gas model

J π : from B(M1)(↓) and B(M1)(↑): new rule? 87 Rb: 845-keV level: 1/2-,3/2- (from L=1) in current ENSDF; 845 gamma to 3/2- g.s. 2 nd excited state in 87 Rb. 2013ST05: PRC 87, (2013): deduced B(M1)(↓) from lifetime measurement of 845-keV level. This value compared with B(M1)(↑) from NRF experiment. Using B(M1)(↓)=[(2J i +1)/(2J f +1)]B(M1)(↑), Authors deduced J f =1/2- for 845-keV level; rejected 3/2-. Authors of above paper state: “ To our knowledge, this is the first time that the spin of an excited nuclear state was determined by measuring the reduced transition strength for both its excitation and deexcitation”.

87 Rb: J π of 845-keV level: PRC 87, (2013)

J π rules: any other from new physics or ideas? Please share with us during the workshop or in the next few weeks.

J π assignments Even-even nuclei: First excited state populated in Coul. Ex.: JPI=2+, MULT=E2 should be a strong argument. (Only exception seems to be 3- in 208 Pb) First 2+ in e-e nuclei: “L(d,d’)=2” argument instead of “E2 gamma to 0+”; Latter is preferred argument.

J π assignments: from gamma decays When no MULT or level lifetime information is available, daughter level JPI known; In general MULT is assumed as E1, M1 or E2. Questions: is it a strong argument or weak? For high- energy gamma rays, should one consider E3, M2, etc. Examples: “gamma to 0+”. Should the assigned JPI=1,2+ or (1,2+) “gammas to 3/2+ and 7/2-”. Should assigned JPI=(3/2-,5/2,7/2+) or 3/2-,5/2,7/2+

J π assignments: from log ft values Many evaluations use log ft arguments when decay schemes seem obviously incomplete. For high Q values, always consider the so-called “pandemonium effect”. Sometimes the authors will say “apparent beta feedings”, consequently “apparent log ft values”. In such cases, log ft values should not be used to assign JPI values. Check if TAGS spectra are available to give some indication of beta feedings distributed over the Q value range.

J π assignments: from log ft values Example: 150 Ho to 150 Dy EC Q(EC)=7364 keV A. Algora et al., PRC 68, (2003): 295 levels up to 5.9 MeV; 1064 gamma rays. Comparison with TAS spectrum shows only 46% of the decay detected through discrete gamma transitions. All deduced beta feedings from gamma-ray data are apparent.

J π and MULT assignments in high-spin data PANDORA’S BOX Authors’ presentation of data and JPI (mult) assignments appear in many different forms. That I think reflects the way these assignments appear in ENSDF, without much consideration for JPI rules in NDS. In most measurements with large arrays: Good multi-fold γγ -coin or (particle) γγ -coin data γ(θ), γγ(θ)( DCO) data; Lifetime data Rare polarization and conversion data Model calculations for band structures considered reliable

J π and MULT assignments in high-spin data Emphasis seems to be on finding Band structures, sequences, or other structure features, rather than on precise determination of energies, intensities, mult, etc. When a long (or short) cascade of gamma rays seen, in most cases it is considered as a sequence of E2 or M1+E2 transitions; the γ(θ), γγ(θ)( DCO) data simply seems to support this, rather than independently determine unique multipolarities. Authors’ assignments: JPI: (Quite often no tabular data) - all without parentheses - some without parentheses, some in parentheses. - all in parentheses

J π and MULT assignments in high-spin data Authors’ MULT assignments: - all MULT assigned as E2, M1, M1+E2 or E1, whether or not there are supporting data. - DCO or angular distribution/asymmetry data given, but only a general statement made about the MULT; no assignments appear with individual gamma rays. - D, Q, D+Q assigned together with supporting data.

J π and MULT assignments in high-spin data In ENSDF, many evaluations follow, almost verbatim, authors’ presentation. MULT given even when no supporting data exist, implied simply from ∆(JPI) based on some band Structure. E2: from DCO=1.39(51) E1: from DCO=0.88(33) (E1): from DCO=0.82(60) E2: from DCO=1.10 (20) E2: from A2=0.20 (5) Other evaluations give D, Q, D+Q etc.