Detailed Spectroscopy at ISOL@MYRRHA

filercaliforniaMechanics

Nov 14, 2013 (3 years and 4 months ago)

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Grupo de Física

Nuclear Experimental

I

E

M

CSIC

María José García Borge

Instituto de Estructura de la Materia, CSIC

β
-
delayed proton Emission:

Peering into Nuclear Structure

Beta
-
delayed

particle

Emission

studies

and

its

Future

@ MYRRHA

Detailed

Spectroscopy

at
ISOL@MYRRHA

Grupo de Física

Nuclear Experimental

I

E

M

CSIC

M. J. Gª Borge, IEM, CSIC, Madrid

Detailed Spectroscopy at ISOL@MYRRHA,23th
-
25th April 2012

B.Jonson & K. Riisager, NPA693 (2001) 77

Beta delayed particle emitters


Close
to

400 nuclei emit
delayed particles



Exotic decays @ drip line

Q
β
d

= 3.0


S
2n

(MeV):
6
He
,
11
Li
,
14
Be,
17
B,
19
B,
22
C

Q
β
t

= 9.3


S
3n

(MeV):
8
He,
11
Li,
14
Be,

17
B,
19
C,
20
C

Qp
α

ó
Q
α
p

:


9
C
,
13
0,
17
Ne
,
23
Si

Grupo de Física

Nuclear Experimental

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M. J. Gª Borge, IEM, CSIC, Madrid

Decay properties of exotic nuclei



Reduced transition probability
:



Global properties



Short half
-
lives (

m




High Q
b

癡汵敳



Low S
p/n

values

b
-
delayed

particle emission

1916
Rutherford & Wood
b

[
Philos. Mag.
31

(1916) 379
]

1963


Barton & Bell

identified
25
Si
as
b
p

E,


䱥癥氠摥湳瑹

印楮Ⱐ䥳潳灩p


b
-
摥捡礠灲潰敲瑩敳

Fermi
Strength

independent

of

Nuclear
Structure

Gamow
-
Teller

strength

obeys

the

Ikeda
sum

Rule

B(GT)
B(F)
C
K
.
.
*
2
2
2
2
2
/
1







A
V
G
G
R
B
T
f
t
f
Detailed

Spectroscopy

at
ISOL@MYRRHA
,23th
-
25th
April

2012

Grupo de Física

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Beta
-
delayed

Neutron

emitters

Neutron
Rich

About

220 cases
measured
,
Mainly

T
1/2
and

P
n
-
values

Spectroscopy

hampered

by
detection

system
!

Compilation

for

fission

products

26 < Z < 58, Pfeiffer,
Kratz
,
Möller
,
Porg
.
Nucl
.
Energy

41(2002)39

a

a

b

b

regr

χ2

Kratz
-
Hermann formula

P
n
≈a
[(
Q
β


S
n
)/(
Q
β



C)]
b


Where

C
is

the

parameter

of

pairing
,
depending

of

even

or

odd

character

of

daughter

nucleus

Grupo de Física

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Detection

Methods

3He
-
spectrometers
.


Energy

異u



䵥M


䱯眠
敦晩e楥湣i



10
-
3






Counter


efficiency



30 %

Depending

of

decay

pattern



Time
-
of
-
Flight

Energy

measurement



500
-
4000
keV

Difficult

to

handle

the

background


M. J. Gª Borge, IEM, CSIC, Madrid

Detailed Spectroscopy at ISOL@MYRRHA,23th
-
25th April 2012

Azuma et al., PRL43 (1979)

+ Digital
electronics


lower

threshold

Grupo de Física

Nuclear Experimental

I

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M. J. Gª Borge, IEM, CSIC, Madrid

Detailed Spectroscopy at ISOL@MYRRHA,23th
-
25th April 2012

Neutron number

Proton number

Z=50

N=50

The Versatile Array of Neutron Detectors at Low
Energy

Beta
-
delayed neutron emitters near
r
-
process path


studied at the HRIBF/
LeRIBSS

in February 2012





VANDLE


2
clovers, 3% efficient @ 1MeV


48 x 60 cm VANDLE bars


45% efficiency/bar @ 1MeV


Ω = 26% of 4
π


12% total efficiency @ 1MeV


Fully instrumented using XIA’s Pixie 16
digitizers




77
Cu (
β
n
)

n
-
Sensitivity

below

100 keV

Courtesy

of

M.
Madurga

Grupo de Física

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M.J.G. Borge, IEM, CSIC, Madrid (Spain)

8

Beta decay of an exotic nuclei

10
Be
+
n

0.504

1974

9
Be
+
2n

7.315

1979

0.320

10.59

8.82

11
Be

20.6

Energías
(MeV)

3/2
-

8
Li
+
t

15.721

1983

Even a neutron rich
-

nuclei
emit charged particles

2

+
3n

8.982

1980

1966

T
1/2

= 8 ms

b
-

8
11
3
Li
17.916

1996

9
Li
+
d

d

9
Li

Talk by Pierre
descouvemont

Grupo de Física

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M. J. Gª Borge, IEM, CSIC, Madrid

Detailed Spectroscopy at ISOL@MYRRHA,23th
-
25th April 2012

Polarized radioactive beams:
11
Li @ TRIUMF

Hirayama, Phys. Lett. B 611 (2005)239

2.6 MeV

11
Be

10
Be

11
Li

8

8.8

3.4 MeV

5.958

5

7

6.179

o
Spin polarized
11
Li beam

o

b
,
b
n,
b
-

-
n
coincidences

o
Spin and parities of 7 levels in
11
Be
assigned.

3/2

3/2

Neutron
-

2590KeV

γ
-
line

Grupo de Física

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M. J. Gª Borge, IEM, CSIC, Madrid

Detailed Spectroscopy at ISOL@MYRRHA,23th
-
25th April 2012

Energy, spin & T
1/2

from

-
lines shape

Mattoon, PRC80
(
2009) 034318

11
Li

8

8.8

Fynbo, NPA 736 (2004) 39

2.6 MeV

3.4 MeV

T
1
/2
(5.96 MeV)
=50
-
60 fs
.

5.958

3/2,5/2

11
Be

10
Be

2
+

2
+

61.5(17)
fs

In a
β
n
γ

process

the

shape

of

broad

γ
-
line

depends

of




The

energy

level

in
11
Be,



Spin
sequence




Lifetime
of

n
-
fed

state

Grupo de Física

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M.J.G. Borge, IEM, CSIC, Madrid (Spain)

11

Universal set
-
up for spectroscopy studies

1.2m

3m

7 x BC501

Liquid scintillator

15 cm x 30 cm

Gamma
detection



3 Glover (4xHPGe)



Ge

2m

Set up:

Cube of DSSSD

4
-
6 Segmented
HPGe

Good scheme for Neutron
detection

Fast Scintillators for T
1/2

Neutron Detection

Need to be improved!!

Grupo de Física

Nuclear Experimental

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M. J. Gª Borge, IEM, CSIC, Madrid

Detailed Spectroscopy at ISOL@MYRRHA,23th
-
25th April 2012

Charged particle emission in the
11
Li
-
decay


Current knowledge:


Four decay channels


Two states in
11
Be: 10.6 and
18.3 MeV
.


Theory: SM predicts

B(GT) strength distribution
peaks between 15 and 20
MeV.



Experiment:


摯灰汥爠
扲b慤敮楮e獵sg敳瑳e獩s湩n楣慮
⠶(⤠⁦敥摩湧潦獴st敳e楮⁴桩猠
牥杩潮⸠


T. Suzuki and T. Otsuka, PRC 56(1997)847

H.O.U. Fynbo et al., NPA736 (2004)39

Grupo de Física

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Deadlayer

and
carbon
-
foil

energy losses corrected



b
-
background subtraction:


E
front
-

E
back



40 keV


M. J. Gª Borge, IEM, CSIC, Madrid

Detailed Spectroscopy at ISOL@MYRRHA,23th
-
25th April 2012

13

Analysis techniques

Energy & momentum
conservation



Momentum
reconstruction


Excitation energy of
the 1
-
2 system:

2
2
1
1
2
1
p
m
p
m
P








0
2
1



n
p
p
p



6
He+



11
Li

Beam

60

术gm
2

Monolithic

detector

Grupo de Física

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M. J. Gª Borge, IEM, CSIC, Madrid

Detailed Spectroscopy at ISOL@MYRRHA,23th
-
25th April 2012

Charged Particle Coincidences


M. Langevin et al.,


NPA 366(1981) 449

D2

D4

127º
-

180º

Grupo de Física

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M. J. Gª Borge, IEM, CSIC, Madrid

Detailed Spectroscopy at ISOL@MYRRHA,23th
-
25th April 2012

Evidence of decay through the
7
He resonance

127º
-

180º

d


10 cm

d


8.5 cm

E
11
Be

E’

6
He+

+n

Q
1

Q
2

7.91

8.33

1
11
11
E
m
m
E
E
Be
Be
'
'


7
He(gs)


Co
ntribution of a new
decay
channel.



Contribution of a state
at 16.3 MeV (


1MeV) ).
In agreement with
theoretical expectations
and previous
b
-
experiment

2005

2007

Grupo de Física

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Kinematic identification of
β
t emission in
11
Li

M. J. Gª Borge, IEM, CSIC, Madrid

Q
β
t
=

M(
11
Li)
-


M(
8
Li)
-


M(t) = 4822(5) keV



P
2

11
Li

Madurga

et al., Eur.
Phys
. J A42 (2009)415



Kinematics

near

180º
between

charged

particles
.



9
Li+
d

channel

stopped
,
9
Li
too

low

recoil

energy
.



The

8
Li+
t

channel

uniquely

separated


Detailed

Spectroscopy

at
ISOL@MYRRHA
,23th
-
25th
April

2012


Measurement

in
other

precursors



The

relation

with

the

structure

of

the

emitting

nucleus

is

less

understood
.



Decay

directly

to

the

continuum
?

Grupo de Física

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B(GT) Distribution for
11
Li from theory

Shell
model

in
s

and
pd

shells


G.
Martinez
-
Pinedo,
PhD

thesis
, UAM, 1995;

M.J.G. Borge et al, PRC 55(1997) R8

H.O.U.
Fynbo
, NPA736(2004)39;

Y.Hirayama

, PLB611(2005)239

17

Experimental bias favors 3/2
-

detection in the
7
He+


channel

Grupo de Física

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M. J. Gª Borge, IEM, CSIC, Madrid


Beta
-
proton emitters



For light nuclei with Z ≥ 8, the IAS
within the Qec window.



From
β
p energy of IAS, Q
EC
-
Sp deduced.


Test
Isobaric Multiplet Mass eq.

M(A,T,T
z
) = a + bT
z

+cT
z
2

+

(dT
z
3
+eT
z
4
)



If
strength to IAS


B
F


Isospin
Mixing


If IAS in the middle of the Q
EC

large part
of the GTGR available => quenching factor
deduced




More than 160 precursors identified



For every element up to Z = 73 at least one proton precursor



The
β
p spectrum depends on the Z and A of the precursor and differs in the
different mass region due to diferences in level density in the Q
-
Sp window



Properties of
β
p well understood


large

variety

of

spectroscopic

information


Detailed Spectroscopy at ISOL@MYRRHA,23th
-
25th April 2012

Yb
151
70
Tm
150
69
Kr
73
36
Ar
33
18
Grupo de Física

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Beta
decay

of

21
Mg

M. J. Gª Borge, IEM, CSIC, Madrid

Detailed Spectroscopy at ISOL@MYRRHA,23th
-
25th April 2012

Counts

Energy (keV)

Strong beta summing

Experiment

Theory

21
Mg

Grupo de Física

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Quenching

factor
of

GT
-
transitions

deduced

M. J. Gª Borge, IEM, CSIC, Madrid

32
Ar

33
Ar

theor
y

theory


Quenching factor

for
Ar’s

close
to one, sensitive to the
placement of the GTGR

33
Ar

β
p



q
=0.58(5)

Comparison

for

resolved
proton

groups

Σ
B
GT

(
theory
)

Σ
B
GT

(
experiment
)

Z.Phys
. A332(1989)413

q = 0.50(5)

The

quenching

factor
q

depends

if

one

uses
individual
transitions

0.49(4)
or

full
distribution
.

Adimi

et al., PRC81(2010) 024311

Detailed

Spectroscopy

at
ISOL@MYRRHA
,23th
-
25th
April

2012

Large

angular
coverage
.

High

efficiency

for

both

proton

and

gammas

Grupo de Física

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βν

correlation

studies
:
peering

into

Nuclear
Structure

María José Gª Borge, IEM, CSIC, Madrid

21


βν

correlation

depends

of

the

type

of

the

transition

Important

probe

of

the

nature

of

weak

interaction


If

the

decay

is

followed

by
particle

emission
,
the

recoil

of

the

daughter

shifts

the

energy

of

the

delayed

particle

by
about

10 keV
that

it

is

easy

to

measure
.

First

used

to

deduced

the

nature

of

the

decay

of

β
2
α

emitter

8
Li

β



ν

correlations

allow

to

extract

spectroscopic

quantities




S
pins
:
31
Ar



Fermi / GT
character



Intrinsic

widths

of

levels



Final
state

(gs/
excited
)
of

delayed

particle


Detailed

Spectroscopy

at
ISOL@MYRRHA
,23th
-
25th
April

2012

The

proton

carries

info

of

the

recoiling

nucleus

at
the

keV
scale

(
A,Z
)

Z > A/2

(A, Z
-
1)

(A
-
1, Z
-
2)

p

Grupo de Física

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32
Ar

0

2.5

3.5

E
p

(MeV)

M.J.G. Borge, IEM, CSIC, Madrid (Spain)

22

Search for New Physics



Set
-
up to avoid
b
-
summing @ ISOLDE

ISOLDE

The V
-
A character of
b
-
decay determined by
measuring
e
-


correlation [Johson,PR132(63)]



If
b
p

emitter


measurement of
e
-


correlation from the broadening of proton peak
from IAS



Isospin

mixing in Fermi decays



Limit for scalar component in beta
decays


M
S
≥ 4.1 M
W




Absolute branching ratios /MSU



Very precise T
1/2

determination /ISOLDE



ft
= 1552(12) s for the Fermi decay



Isospin Symmetry breaking Correction



c

= 2.0(4) %

Bhattacharya et al.,
PRC77 (2008) 065503

MSU

32
Ar

p

b
+p

32
Cl

31
Sl



e
+

3.35
MeV

5.1 MeV

370 eV

100
keV

p

2

MeV

4

3

Grupo de Física

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M. J. Gª Borge, IEM, CSIC, Madrid

Mapping of
Neutron
Deficient

nuclei 22 < Z <
28

Spectroscopy

studies

with

b
-
p
-

,
b
-




23 isotopes
Studied


Macroscopy

Properties

:

T
1
/
2
,

P
p



Spectroscopy
:



Partial
Decay

scheme


IAS Identification



IMME


Dossat

et al., NPA702 (2007) 18

46
Mn

43
Cr

β2p ?

β2p + β3p
observed
.

12 %
feeding

to

bound

states

Pomorski

PRC 2011

Detailed Spectroscopy at ISOL@MYRRHA,23th
-
25th April 2012

Grupo de Física

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From

peaks

to

continua (Hardy,
Cargese
, 1976)

M. J. Gª Borge, IEM, CSIC, Madrid

(Z
-
1,N+1)


(
Z,N
)

(Z
-
2,N+1)+
p

Q
EC

Sp

Q
β
+



β
p

explored

high

excitation

energy

in
the

daughter

=> individual
transition

are
not

longer

resolved




To

fit

the

proton

spectrum

average
of

the

above

quantities

are
considered
.


β
p

+ X
-
Ray ratio
strongly

constraint

the

level

density

distribution




Good

estimate

of

proton

and

gamma
widths

for

exotic

nuclei

of

interest

for

nucleosynthesis


The

Porter Thomas
distribution

accounts

of

the

fluctuations

observed

in
the

spectrum


Giovinazzo

et al, NPA674 (2000) 394

Detailed Spectroscopy at ISOL@MYRRHA,23th
-
25th April 2012

Grupo de Física

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β
-
delayed

2p
-
emitters

M. J. Gª Borge, IEM, CSIC, Madrid

Most

of

the

cases
only

the

emission

from

the

IAS
identified
.

The

decay

has
been

identified

as
sequential

in
the

few

cases
where

2p
-
emission

has
been

studied

in
detailed
:
22
Al,
26
P,
31
Ar,
45
Fe,
43
Cr

β
-
3p
finally

identified

in
45
Fe &
43
Cr

Characterization

of

states

near

particle

threshold

of

astrophysical

relevance
.


9
β
2p
emitters

identified

β3p

β3p

Detailed Spectroscopy at ISOL@MYRRHA,23th
-
25th April 2012

31
Ar
remains

as
the

easier

case
to

search

for

p
-
p

correlations

due

to

production
.

Study

27
S
very

interesting
:


Too
low

β
p

and

β
2p, Eur.
Phys
. J. A12
(2001) 377


Grupo de Física

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M. J. Gª Borge, IEM, CSIC, Madrid

31
Ar
b
-
2p emitter

Decay of IAS through

2p emission

Diagonal from decays via single

intermediate state from many

initial states fed in beta
-
decay

1p
-
spectrum.

2p
-
spectrum

Detailed Spectroscopy at ISOL@MYRRHA,23th
-
25th April 2012

Grupo de Física

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Gamow
-

Teller

2p
-

transition

M. J. Gª Borge, IEM, CSIC, Madrid

Detailed Spectroscopy at ISOL@MYRRHA,23th
-
25th April 2012

1st emitted

2nd emitted

30
S*

29
P

Isospin

allowed
transitions
increasing number
of
intermediate states possible


p
D
p
D
p
E
E
M
m
E
M
m
E
E
2
'
2
1
1
1
2
1
'
2
2
cos














Kinematics of sequential emission



2
He branch present at some level
?

Grupo de Física

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María José Gª Borge, IEM, CSIC, Madrid

28

31
Ar

: a new look

Astrophysical interest
:

The

29
P
(p,

)
30
S
reaction
rate depends of the 4.5
-
5.5 MeV states in
30
S

β
-
2p
proton

spectrum



excited

unbound

states

in
30
S

p1

Mirror

Nucleus

5/2
+

5217

In
previous

work
,
the

5.136
keV
state

was

first

assign

as
0
+

or

3
+
.
And

recently

as 4
+


5,21
MeV

Fynbo

et al., NPA A677 (2000) 38

Grupo de Física

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M. J. Gª Borge, IEM, CSIC, Madrid


-
spectrum

1193


1406


2210

2477


3405

2921

30
S

5,21
MeV

3
+

4
+

5217

Our

β2p
decays

mainly

populate

a
level

at 5217.4(7) keV
that

decay

to

29P ½+
by 600 keV.


The

penetrabilities

were

for


600 keV
proton



L= 0 P = 8.7
x

10
-
4




L = 2 P = 2.5
x

10
-
5



L=4 P = 6.7
x

10
-
8

L=4 imposible

Detailed

Spectroscopy

t

ISOL@MYRRHA
,23th
-
25th
April

2012

8

The

3
+

state

in
30
S
also

identified

in

reaction

work
.


Setoodehnia

et al. PR C82 (2010) 02280 :
32
S(
p,t
)
30
S

PR C83 (2011) 018803:
28
Si(
3
He,

)
30
S

Spin
of

5.1 & 5.2
MeV

levels

deduced

from

particle

penetrability

Beta
-
decay

study

the

only

opportunity

to

determine
the

state

proton
/gamma
width

Study
30
S levels from
31
Ar decay

Grupo de Física

Nuclear Experimental

I

E

M

CSIC

M. J. Gª Borge, IEM, CSIC, Madrid

Summary & Outlook @ MYRRHA



Exotics decays
: Nature of
β
t


湥眠
捯湤楤慴敳

14
Be…(10
-
4
)




Use
of

Polarised

beam
.


Angular
correlations

studies



Mapping

the

change

of

structure

in
the

β
p

spectrum

from

peaks

to

continuum



Determination

of

Γ
Υ

/
Γ

and

Γ
p

or

Γ
α

/
Γ

of

astrophysical

relevance



β
2p
should

be
explored

in
detail

in
other

candidates

mainly

27
S
and

35
Ca


Search

for

p
-
p

correlation

in
excited

state










Particle emission studies done with
high precision
are an
unbeatable

probe
of nuclear

structure at
the microscopic level

Detailed

Spectroscopy

at
ISOL@MYRRHA
,23th
-
25th
April

2012