Study of neutron-deficient nuclei below 100Sn

“Universa Universis Patavina Libertas”

1. Physical motivations

2. Experimental details

A. Gottardo, J.J. Valiente-Dobon,…

IntroductionIntroduction

The evolution of nuclear structure at the extremes of isospin is one of the major topics in modern nuclear

physics

The proton-rich nuclei close to the N = Z line below mass 100 are known to exhibit a variety of interesting phenomena: 1p and 2p radioctivity and higher-lying

spin-gap isomers

The proton-rich nuclei close to the N = Z line below mass 100 are known to exhibit a variety of interesting phenomena: 1p and 2p radioctivity and higher-lying

spin-gap isomers

Two-proton radioactivity in 94Ag

Spin-gap and seniority isomers Rp-process

94Ag (1)94Ag (1)

The 2p radioactivity strength suggest a very deformed

(3:1) 21+ isomer

The 2p radioactivity strength suggest a very deformed

(3:1) 21+ isomer

Nature, 439, 298 (2006)

This N = Z nucleus has two isomers (7+, 21+, t1/2 ~ 0.5 s), with the highest one decaying via one and two-proton

emission

This N = Z nucleus has two isomers (7+, 21+, t1/2 ~ 0.5 s), with the highest one decaying via one and two-proton

emission

The 21+ isomer also decays by two different 1p emission

PRL 95, 022501 (2005)

94Ag (2)94Ag (2)Mass measurements,

detailed γ spectroscopy of the daughter nucleus and following experiment did

not confirm the 2p emission… further studies

needed

Mass measurements, detailed γ spectroscopy of the daughter nucleus and following experiment did

not confirm the 2p emission… further studies

needed

The γ spectroscopy of 94 Ag will provide valuable information on nuclear structure in this N =Z nucleus, in particular

clarifying the structure above the proton-emitting isomer. T= 0 aligned pairing?

The γ spectroscopy of 94 Ag will provide valuable information on nuclear structure in this N =Z nucleus, in particular

clarifying the structure above the proton-emitting isomer. T= 0 aligned pairing?

PRC 77, 064304 (2008)

96Cd96CdThe 100Sn nucleus is a fundamental step in

uderstanding the nuclear force and the nuclear structure

The isotopes below 100Sn, with protons and neutrons filling the

g9/2 shell up to N,Z = 50, are crucial to infer the evolution of nuclear

structure towards the shell closure

A 16+ spin-gap isomer is predicted and decay spectroscopy has been

performed at GSI (FRS-Rising)

It is fundamental to also have prompt-spectroscopy data!

Acta Phys. Pol. B, 40, 611 (2009)

100In100In

In prompt spectroscopy we expect to see states from the πg9/2

-1-νd5/2 and πg9/2-1-νg7/2 multiplets, and perhaps

excitations of the 100Sn core for spins higher than 8+

100In is a 1p-hole – 1n-particle nucleus with respect to 100Sn: ideal case to study pn

interaction

Direct extraction of pn matrix elements Direct extraction of pn matrix elements

PRC 65, 021302(R) (2002))

101Sn101Sn

States from νd5/2 and νg7/2, νh11/2 are expected, together with the

excitation of the 100Sn core

101Sn is fundamental nucleus in shell model, being one neutron above 100Sn: ideal case to

study the double shell closure and the effect of tensor interaction

Ongoing discussion on the inversion of νd5/2 and

νg7/2, linked to tensor force

Ongoing discussion on the inversion of νd5/2 and

νg7/2, linked to tensor force

PRL 105, 162502 (2010))

How to study these nuclei?How to study these nuclei?

Gamma array: Agata, Galileo, Exogam2

Neutron array:

Neda

1. Channels with evaporation of 3 neutrons: 3n, 1p3n…

2. Channels with evaporation of 2 neutrons: 2n, 1p2n…

Fusion evaporation- reactions: proton-rich, high spin population

Fusion evaporation- reactions: proton-rich, high spin population

Charged particles:Diamant, Trace

Batch mode for exotic beamsBatch mode for exotic beamsPrimary proton

beam from cyclotron: 70MeV,

0.8 mA

The target then becomes the

source of the LNL TANDEM

Irradiation of a target to produce

56Ni

Irradiation of a target to produce

56Ni

Fusion-evaporation reaction with

NEDA – TRACE – AGATA/GALILEO

94Ag94Ag

Cross section ~ 50 μb

40Ca + 58Ni

p3n evaporation

40Ca + 56Ni

p1n evaporation

Cross section ~ 100 μb

Beam current > 10 pnA

Beam current ?

Beam to be produced in batch mode at LNL-SPES

Three – neutron detection efficiency ~ 0.1%

One – neutron detection efficiency ~ 25%

94-96Cd94-96Cd

Cross section ~ 100 μb - 6 μb

40Ca + 58Ni

2n-3n evaporation (95-

96Cd)

40Ca + 56Ni

1n?-2n evaporation (94-

95Cd)

Cross section ~ 150-9 μb

Beam current > 10 pnA

Beam current ?

Beam to be produced in batch mode at LNL-SPES

Three – neutron detection efficiency ~ 0.1%

Two – neutron detection efficiency ~ 5%

100In100In

Cross section ~ 4 μb

58Ni + 45Sc

3n evaporation

56Ni + 46Ti

pn evaporation

Cross section ~ 20 μb

Beam current > 10 pnA

Beam current ?

Beam to be produced in batch mode at LNL-SPES

Three – neutron detection efficiency ~ 0.1%

one – neutron detection efficiency ~ 25%

101-100Sn101-100Sn

Cross section ~ 4 μb

58Ni + 56Ti

3n evaporation:101Sn

56Ni + 56Ti

2n evaporation 100Sn

Cross section ~ 10 μb

Beam current > 10 pnA

Beam current ?

Beam to be produced in batch mode at LNL-SPES

Three – neutron detection efficiency ~ 0.1%

Two – neutron detection efficiency ~ 5%

ConclusionsConclusionsPhysics case to study many proton-rich nuclei below

A=100:

Attempts already done at Argonne with GS-FMA

The identification of evaporated neutrons and protons to select the reaction channel is a powerful tool to study exotic nuclei (better efficiency than FMA?)

The future avalability of 56Ni beam with the batch-mode technique will enable to study very exotic nuclei exploiting the capabilities of NEDA at full