ENSDF: Consistency (or lack thereof) in Jπ assignments (including Multipolarities)

Balraj Singh

McMaster University, Canada

IAEA-ENSDF Workshop, Vienna

April 27-29, 2015

Nomenclature of Jπ in data record in ENSDF

Jπ = 2+

2(+)

(2)+

(2+)

(2)

+

(+)

[2+]

J1 AP 10; J2 AP 11

NOT 3

NATURAL, UNNATURAL

Jπ = 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+)

----------------------------------------

Jπ =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 Jπ assignments (see policy document). No such document for MULT assignments (implicit in Jπ 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?

Jπ / Mult assignments in Adopted and Individual decay/reaction data sets.

Policy: Reaction and decay data sets items #1, 2, pages i, ii:

“The Jπ values in decay data sets are taken from the associated Adopted Levels, Gammas data set.

For reaction data sets, the Jπ 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 Jπ values as in paper; but MULT assignments should be based on rules. Jπ values in Adopted data set should be listed in comments, if different from those in reaction data set.

Jπ 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 Jπ 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?

Jπ 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

Jπ 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.

Jπ : isobaric analog states/resonances

Observation of (very) strong peaks in particle-transfer data such as (3He,p), (p,3He), (3He,t), (3He,d), etc.

44Ca(3He,t)44ScPRC 88, 014308 (2013)

2nd most intense peak at

2779 keV; IAS of 44Ca g.s.

1971INZU: priv. comm.37Cl(3He,d)38Ar

Strong peaks at

10.63, 11.30, 11.35.

11.39, 11.93 MeV: IAR of 38Cl levels

Jπ: current rules: silent for several reactions

2-particle transfer reactions:

(3He,p); (p,3He), and perhaps others.

Note: for (p,t); (t,p); (3He,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: (3He,t); (t,3He); (p,n), etc.

Inelastic scattering experiments:

(p,p’); (d,d’); (n,n’); (3He,3He’), 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

Jπ assignments: mirror nuclidesD. Doherty et al., PRL 108, 262502 (2012)

Jπ assignments: R-matrix analysis: J. Chen et al., PRC 85, 015805 (2012)

Jπ : new rules?

Statistical analysis of gamma transitions in complex level schemes, such as in (n,γ):

DICEBOX computer code.

Example: 2013Fi01.: PRC 87, 024605 (2013)

E1: Standard Lorentzian model

M1: Single-particle modelLevel density: Back-shifted Fermi gas model

Jπ : from B(M1)(↓) and B(M1)(↑): new rule?

87Rb: 845-keV level: 1/2-,3/2- (from L=1) in current ENSDF;

845 gamma to 3/2- g.s. 2nd excited state in 87Rb.

2013ST05: PRC 87, 037302 (2013): deduced B(M1)(↓) from lifetime measurement of 845-keV level.

This value compared with B(M1)(↑) from NRF experiment.

Using B(M1)(↓)=[(2Ji+1)/(2Jf+1)]B(M1)(↑),

Authors deduced Jf=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”.

87Rb: Jπ of 845-keV level: PRC 87, 037302 (2013)

Jπ rules: any other from new physics or ideas?

Please share with us during the workshop or in the next few weeks.

Jπ 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 208Pb)

First 2+ in e-e nuclei:

“L(d,d’)=2” argument instead of “E2 gamma to 0+”;

Latter is preferred argument.

Jπ 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+

Jπ 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.

Jπ assignments: from log ft values

Example: 150Ho to 150Dy EC Q(EC)=7364 keV

A. Algora et al.,

PRC 68, 034301 (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.

Jπ and MULT assignments in high-spin dataPANDORA’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

Jπ 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

Jπ 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.

Jπ 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.