Gamma-ray spectroscopy of semi-magical 131Sn

High-Resolution In-Beam Spectroscopy of 131Sn81

Precise location of the neutron single-particle states &

First measurement of neutron transfer on an isomer

Anissa Bey University of Tennessee, Knoxville

JIHIR, ORNL

XXXIII Mazurian Lakes Conference on Physics - Frontier in Nuclear Physics Piaski, Poland, 1-7 September, 2013

Piaski|03/09/2013

R-process in the vicinity of 132Sn

A. Bey High-Resolution In-Beam Spectroscopy of 131Sn81 Piaski|03/09/2013 2/13

from J.J. Cowan et al., Physics Today 47 (2004)

Z=50

N=82

Limit of laboratory

experiments

r-process path

R-process

Nucleosynthesis mechanism responsible for

production of approx. half of heavy elements

beyond iron (A=70) peak

Interplay between rapid neutron captures (n,),

photo-dissociation (,n), and -decay

Crucial inputs

Masses, half-lives, and -n ratios

R-process in the vicinity of 132Sn


from J.J. Cowan et al., Physics Today 47 (2004)

Z=50

N=82

Limit of laboratory

experiments

r-process path

R-process

Nucleosynthesis mechanism responsible for

production of approx. half of heavy elements

beyond iron (A=70) peak

Interplay between rapid neutron captures (n,),

photo-dissociation (,n), and -decay

Crucial inputs

Masses, half-lives, and -n ratios

Late times, freeze-out stage, (n,) captures on

some “seed” nuclei can be decisive in defining

the final isotopic abundance pattern

Case with 130Sn

However!

R. Surman et al., PRC 64, 035801 (2001)

& PRC 79, 045809 (2009)

Freeze-out direct (n,) captures on 130Sn

N=82

Z=50 130Sn

3.72 m

131Sn

-56 s

132Sn

39.7 s

130In

0.29 s

131In

0.28 s

130Cd

162 ms

131Cd 132Cd

(n,)

-

(,n)

Adapted from:

R. Surman et al., PRC 79, 045809 (2009) ------------

J. Beun et al., JPG-NPP 36, 025201 (2009)

At R-process late times

Path nucleus 130Cd is highly populated

Significant amount of material is collected in 130Sn

Flow of material along Z=50 is sensitive to DC(n,) on 130Sn


Isotopic abundance sensitivity to (n,) captures on 130Sn

Abundance changes under increase of 130Sn(n,)131Sn rate by x100

12% overall on average

34% around A~195

191% near A~131

J. Beun et al., JPG-NPP 36 (2009)

130Sn Rate x 10 132Sn Rate x 10


DC(n,) sensitivities

FRDM

RMFT

HFB

Mass number A

Cro

ss s

ecti

on

[b

arn

]

(n,) cross-sections at 30 keV

In Sn isotopes, DC(n,) dominated by

captures to p-shell orbitals (3p1/2,3p3/2)

Largest dependencies of DC(n,)

on spin-parities J & energies Ex of

given individual shell model states


T. Rauscher et al., PRC 57, 4 (1998)

2h-1p excitations or single-particle states in 131Sn81 ?

130Sn(d,p)131Sn - R.L. Kozub et al.

Population of 4 lowest shell model states

S.F.s support a single-particle nature

131Sn Spectroscopic Factors (S.F.s)

DWBA calculations ( 30% uncertainty)

Neutron-rich beams transfer studies at HRIBF - ORNL

0.7

0.7 1.0

0.75

R.L. Kozub et al., PRL 109 (2012)






Limited resolution; no GS population

Particle (d/d) insensitive to spin

(d,p) not well-matched to populate higher -----

----spin shell model states (1h9/2, 1i13/2)




0.7

0.7 1.0

0.75

R.L. Kozub et al., PRL 109 (2012)






Limited resolution; no GS population

Particle (d/d) insensitive to spin

(d,p) not well-matched to populate higher -----

----spin shell model states (1h9/2, 1i13/2)



130Sn(9Be,8Be-) & (13C,12C-) - This work

In-beam -ray spectroscopy

precise energy location

infer spin from angular correlations


0.7

0.7 1.0

0.75

R.L. Kozub et al., PRL 109 (2012) 2 targets (13C, |1p1/2) and (9Be, |1p3/2)

different transfer matching conditions

probe spin selectivity


High-resolution heavy-ion transfer experiments at HRIBF

HYBALL

CLARION

Monitoring and diagnostics

40 CsI(Tl) + photodiodes for particle-tagging

11 HPGe segmented Clovers + Compton suppression BGOs

0 deg. Bragg detector

Beam

Highly-purified 130SnS @ 4 MeV/u

7-12x105 part./s for this run

4 days of data taking

Targets 9Be (2.005 mg/cm2) 13C (1.975 mg/cm2)

Particle- coincidence setup @ HRIBF


-ray emission: single-particle states


-ray emission: single-particle states

A. Bey et al., to be published (2014)

single-neutron states partial level scheme

3p1/2

3p3/2


-ray emission: 1h11/2 orbital position

Previously

Decay spectroscopy measurements

Fogelberg et al., PRC 70, 034312 (2004)

- 69 (14) keV / Q

- 65.1 keV / M2 -transition

Fogelberg et al., PLB 137, 20 (1984)

- 160 (100) keV / Q

- 242 keV / another M2 -transition


-ray emission: 1h11/2 orbital position

This work

X (7/2- 5/2+) = 68(1) keV

Previously

Decay spectroscopy measurements

Fogelberg et al., PRC 70, 034312 (2004)

- 69 (14) keV / Q

- 65.1 keV / M2 -transition

Fogelberg et al., PLB 137, 20 (1984)

- 160 (100) keV / Q

- 242 keV / another M2 -transition


-ray emission: high-spin states

Energies known from Cm source fission

fragments studies @ Gammasphere

--Bhattacharyya et al., PRL 87,6 (2001)

But assigned to high-spin states (very

high spin ~ 19/2+!!)

How to explain present population??


130Sn 7- (1.7 min) isomer: nuclear structure point


Single-neutron hole & particle states at Z=50/N=81

130Sn 7- (1.7 min) isomer: nuclear structure point

Theory QMSSM, Insolia et al., NPA 550, 34 (1992)

Oxbash Shell Model - G-matrix + SN100PN interaction

A. Brown et al., PRC 71, 044317 (2005) & D.S. Judson, Ph.D. thesis (2007)

7- : ~98% |d3/2|h11/2

shell model state!


Single-neutron hole & particle states at Z=50/N=81

131Sn81: the yrast band via single-neutron transfer

Seniority 2 -configurations

Level assignments and structure interpretation Bhattacharyya et al., PRL 87,6 (2001)

f7/2 d3/2-1

h11/2-1

1h11/2

2d3/2

10

2f7/2

1h11/2

2d3/2

10

2f7/2

7-


Summary & Outlook

Precise location of the astrophysically relevant

shell-model states in 131Sn

Population of select members in 131Sn ~5.0

MeV yrast band via direct single-neutron transfer

Measured -p -h -ray cross transition

yields 68 1 keVstat. for 1h11/2 orbital in 131Sn

Further evidence supporting the robustness of

the 132Sn doubly-magic core

Updated DC(n,) calculations and R-process

simulations

Nuclear shell structure theory to interpret our

new data (core excitations, fragmentation & level

density, EM properties & lifetimes...)

Single-neutron states across 132Sn82

…and more if

133Sn: K.L. Jones et al., Nature 465, 454 (2010) 131Sn: A. Bey et al., to be published (2014)

Sn: ISOLTRAP (2008), JYFLTRAP (2012), CPTRAP

(2013) mass measurements


Gamma-ray spectroscopy of semi-magical 131Sn

Science

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