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L.M. Fraile for the ISOLDE L.M. Fraile for the ISOLDE IS414 collaborationIS414 collaborationCERN CERN –– PH/ISOLDEPH/ISOLDE
Advanced Time Delayed βγγ(t) measurements in the N~20 island of inversion
SLAFNAP6, Iguazú, October 2005
Advanced Time Delayed Advanced Time Delayed βγγ βγγ(t) measurements (t) measurements in the N~20 island of inversionin the N~20 island of inversion
SLAFNAP6, Iguazú, October 2005
L.M. Fraile SLAFNAP6, Iguazú 2005
The N~20 island of inversionThe N~20 island of inversion
Cl31
Cl32
Cl33
Cl34
Cl35
Cl36
Cl37
Cl38
Cl39
Cl40
Cl41
Cl42
Cl43
Cl44
Cl45
Cl46
Cl47
Cl48
Cl49
Cl51
16 S27
S28
S29
S30
S31
S32
S33
S34
S35
S36
S37
S38
S39
S40
S41
S42
S43
S44
S45
S46
S47
S48 34
P26
P27
P28
P29
P30
P31
P32
P33
P34
P35
P36
P37
P38
P39
P40
P41
P42
P43
P44
P45
P46 32
14 Si22
Si23
Si24
Si25
Si26
Si27
Si28
Si29
Si30
Si31
Si32
Si33
Si34
Si35
Si36
Si37
Si38
Si39
Si40
Si41
Si42 30
Al22
Al23
Al24
Al25
Al26
Al27
Al28
Al29
Al30
Al31
Al32
Al33
Al34
Al35
Al36
Al37
Al38
Al39 28
12 Mg20
Mg21
Mg22
Mg23
Mg24
Mg25
Mg26
Mg27
Mg28
Mg29
Mg30
Mg31
Mg32
Mg33
Mg34
Mg35
Mg36 26
Na19
Na20
Na21
Na22
Na23
Na24
Na25
Na26
Na27
Na28
Na29
Na30
Na31
Na32
Na33
Na34
Na35
10 Ne16
Ne17
Ne18
Ne19
Ne20
Ne21
Ne22
Ne23
Ne24
Ne25
Ne26
Ne27
Ne28
Ne29
Ne30
Ne32 24
F15
F16
F17
F18
F19
F20
F21
F22
F23
F24
F25
F26
F27
F29 22
8 O12
O13
O14
O15
O16
O17
O18
O19
O20
O21
O22
O23
O24 18
20N11
N12
N13
N14
N15
N16
N17
N18
N19
N20
N21
N22
N23
6 C8
C9
C10
C11
C12
C13
C14
C15
C16
C17
C18
C19
C20
C22
6 84 10 12 14 16
Island of inversionWarburton et al., PRC41 (1990) 1147
New region of deformation…WHY?
WHERE?
Ground state propertiesThibault et al., PRC12 (1975) 644Huber et al., PRC18 (1978) 1978
DeformationDetraz et al., PRC19 (1979) 164Motobayashi et al., PLB346 (1995) 9Keim et al., EPJA8 (2000) 31Pritychenko et al., PRC63 (2000) 011305(R)
L.M. Fraile SLAFNAP6, Iguazú 2005
The N~20 island of inversionThe N~20 island of inversion
Breakdown of N=20 shell → pf particle-hole excitations.
S2n of 30Na compared to the shell-model calculations. Corresponding dominant neutron configurations of the ground state and the ESPE’s obtained from each interaction.
E. Caurier et al., NPA 693 (2001) 374
L.M. Fraile SLAFNAP6, Iguazú 2005
T. Otsuka et al., EPJA 15 (2002) 151Y. Utsuno et al., PRC 70 (2004) 044307
The N~20 island of inversionThe N~20 island of inversion
Neutron Effective Single Particle energies for 30Si and 24O, relative to 1s1/2. The change is due to the strongly attractive interaction between a proton in 0d5/2 and a neutron in 0d3/2.
Sketch of the sources of the correlation energy of the intruder and the normal states of semi-magic and open-shell nuclei.
L.M. Fraile SLAFNAP6, Iguazú 2005
The Advanced Time Delayed The Advanced Time Delayed βγγ βγγ(t) method(t) method
Ge-1BetaBaF
2 -1
BaF 2-
2
ISOLDE beam
Detectors• 1 Beta and 2 BaF2: timing• 2 Ge: E resolution, selection of decay branches
Triple coincidence events:
• β–BaF2–Ge: lifetime measurements
• β–Ge–Ge: coincidences, level scheme
Method:
• De-convolution: ns range
• Centroid shift: 10’s of ps H. Mach et al., NPA 523 (1991) 197
βγγ(t) setup @ ISOLDE
L.M. Fraile SLAFNAP6, Iguazú 2005
Experimental investigation of 30,31,32Mg• 30,31Mg: coexistence of spherical and intruder configurations
• Excited states not clearly characterized• Candidate for 0+ in 30Mg?
• 32Mg: half-life of the first excited 2+ state (885 keV)• Other nuclei observed in β-decay: 33,34Mg
Experiments performed at ISOLDE at CERN• October 2003 (30,31,32Na decays)
• August 2004 (30,32Na decay)
• August 2005 (30,32,33Na decay)
The IS414 experimentThe IS414 experiment
L.M. Fraile SLAFNAP6, Iguazú 2005
The intruder structure in The intruder structure in 3030MgMg
→ Timing: 306-1482 cascade
L.M. Fraile SLAFNAP6, Iguazú 2005
3030Na decayNa decay
L.M. Fraile SLAFNAP6, Iguazú 2005
Beta-Ge-Ge
Beta-Ge-BaF2(t)
Fast timing: 1482 – 306 keV
A long lifetime of the 1789 keV state makes it a natural candidate for the intruder 0+ state. But there is a 1789 keV gamma to the g.s.
Beta-BaF2(t)
3030Mg: fast timingMg: fast timing
L.M. Fraile SLAFNAP6, Iguazú 2005
3030Mg: Evidence for 0Mg: Evidence for 0++ candidatecandidate
Gate on 3178 keV
1482
Gate on 1789 keV
1482
1820
Gate on 1820 keV
1482
1789
Coincidences:The 3178 gamma feeding the 1789 keV
level from above shows no coincidences with the 1789 keV line.
There is clear evidence for a 1482-1820-1789 keV cascade defining a new level at 3302.3 keV.
L.M. Fraile SLAFNAP6, Iguazú 2005
3030Mg: proposed level schemeMg: proposed level scheme
There is now an intensity imbalance for the 1789 keV state: with 6.6(4) feeding and 4.8(3) de-exciting the state = 1.8(5).
Below 3.3 MeV there are now only 3 known excited states in 30Mg: 2+ 1482, (0+) 1789, and (2+) 2467 keV.
L.M. Fraile SLAFNAP6, Iguazú 2005
B(E2; 21+ → 01+) = 40(9) e2fm4 (Scheit et al.)
B(E2; 21+ → 02+) = 10.8(11) e2fm4
B(E2; 22+ → 21+) > 123 e2fm4 (if pure E2; likely M1)
Strenght of E0 02+ → 01+ ?
3030Mg: the intruder structureMg: the intruder structure
There are close-lying 22+ and
23+ states in 28Mg: 22+ decays
only by an M1 transition to the
21+ state, while 23+ decays by a
strongly mixed M1+E2 transition
to 21+ and by an E2 to 01+. The
2467 state could be equivalent
to the 22+ case.
R. Rodriguez-Guzman et al., NPA 709 (2002) 201
L.M. Fraile SLAFNAP6, Iguazú 2005
Study of Study of 3131MgMg
The 461 and 1154 keV levels are populated in the beta-delayed neutron emission of 32Na, while the other states are populated in the decay of 31Na.
New 1/2+ 2p2h configuration of the ground state [Neyens et al. PRL 94 (2005) 22501].
New possible location of the 1p1h 11/2− state included coming from our coincidence data.
Lifetimes: expected long lifetime for the 461 keV level (7/2−).
L.M. Fraile SLAFNAP6, Iguazú 2005
These and other experimental results confirm the model interpretation of the observed states in 31Mg, they do not provide a unique identification.
The measured lifetimes provide strong constraints on any alternative interpretation of these states
The 461 keV state is the 1p1h intruder:
The 240 keV ray is the collective E2 7/2− → 3/2− transition.
B(E2) = 67(6) e2fm4
B(E2; 2+ → 0+) = 67(14) e2fm4 for the 2p2h configuration in 32Mg [B.V. Pritychenko et al., PLB 461(1999) 322]
Study of Study of 3131MgMg
L.M. Fraile SLAFNAP6, Iguazú 2005
Lifetime of the 2Lifetime of the 2++ state in state in 3232MgMg
Centroid shift technique using a
two gamma ray cascade involving
beta and 2151-885 keV gammas.
Important is to select beta sources
providing time response calibrations
of the BaF2 detectors for the full
energy peaks matching as close as
possible the energies of 2151 and
885 keV, and cascading via levels of
precisely known lifetimes.
Calibration sources: 88Rb (energies 898-1836 keV), 30Al (1263-2235 keV), 24Na (1369-2754 keV), and other.
L.M. Fraile SLAFNAP6, Iguazú 2005
Data Set 1
Ge-1 energy projection Gates in gamma detectors are selected only on the full-energy gamma peaks
Beta energy
Triple coincidences:Beta-Ge-GeBeta-Ge-BaF2(t)
3232Mg: the 885Mg: the 885--2151 keV cascade 2151 keV cascade
L.M. Fraile SLAFNAP6, Iguazú 2005
BaF2 and Ge-2 gated spectra by the 885 and 2151 keV gamma peaks
3232Mg: the 885Mg: the 885--2151 keV cascade 2151 keV cascade
L.M. Fraile SLAFNAP6, Iguazú 2005
3232Mg: the 885Mg: the 885--2151 keV cascade 2151 keV cascade
Beta-BaF2(t) Time-delayed spectra with a Ge gate
L.M. Fraile SLAFNAP6, Iguazú 2005
Time response curveTime response curve
Two-point calibrations for
the energy pairs 898-1836,
1263-2235, and 1369-2754
keV.
Time response calibration
curve for the region 898-2754
keV.
Other data confirm good
linearity over the region 898-
2235 keV and a small
bending down above (due to
limits on the CFD input
range).
The
precision of
the error bars
is as low as
0.6-0.7 ps.
The line is set
to cross zero at
885 keV.
L.M. Fraile SLAFNAP6, Iguazú 2005
HalfHalf--life of the 885life of the 885--keV level in keV level in 3232MgMg
Centroid Shift for 32Mg from 1 data set
Cascade 2151-885Shift due to the lifetime of the 2+
state at 885 keV
T1/2(2+) = 16.0(4.2) ps B(E2; 01+ → 21+) = 327(87) e2fm4
L.M. Fraile SLAFNAP6, Iguazú 2005
3232Mg lifetime from two data setsMg lifetime from two data sets
T1/2(1) = 16.0(4.2) ps
T1/2(2) = 13.6(6.1) ps
B(E2) = 342(78) e2fm4
T1/2average = 15.3(3.5) ps
Expected final uncertainty of ~2.5 ps
Data Set 2
L.M. Fraile SLAFNAP6, Iguazú 2005
[from O. Niedermaier]
Low E CoulEx, Timing
Intermediate E CoulEx
B(E2)B(E2)’’s for Mg isotopess for Mg isotopes
ATD
L.M. Fraile SLAFNAP6, Iguazú 2005
Status IS414Status IS414
• New states identified in 30MgEvidence for the 0+ intruder state in 30Mg
• Direct lifetime measurement of the 885 keV 2+ state in 32Mg
Currently T1/2 = 15.3(3.5) ps.
The analysis is in progress; further improvement is expected. The final aim is ~2 ps error.
• New fast timing measurements run on 33Mg and 32Mg in 2005
• Search for the E0 transitions in 30Mg also performed in 2005
L.M. Fraile SLAFNAP6, Iguazú 2005
New Fast Timing Crystals and New Fast Timing Crystals and PhototubesPhototubes
New crystals are being produced with much improved energy resolution, yet not as good timing resolution as BaF2.
The energy resolution of LaBr3:Ce is about 2.7% at 661 keV in comparison to 6% for NaI:Tl and 9-10% for BaF2.
Strong time decay variation is observed for LaBr3 for 0.5% doping with Ce (A) and 4% (B), compare to NaI:Tl (C).
[P.Derenbos et al., IEEE Trans.Nucl.Scien. 51 (2004) 1289]
Many other references!
L.M. Fraile SLAFNAP6, Iguazú 2005
The IS414 CollaborationThe IS414 Collaboration
H. Mach, M.J.G. Borge, R. Boutami, P.A. Butler, J. Cederkäll, P. Dessagne, B. Fogelberg, H. Fynbo, R. Gernhauser, P. Hoff. A. Jokinen, C. Jollet, A. Korgul, U. Köster, T. Kröll, W. Kurcewicz, F. Marechal, T. Motobayashi, J. Mrazek, G. Neyens, T. Nilsson, W. Płóciennik, S. Pedersen, A. Poves, B. Rubio, E. Ruchowska, M. Stanoiu, W. Schwerdfeger, O. Tengblad, P. Thirolf, D.T. Yordanov and the ISOLDE collaboration
Uppsala University, Studsvik, SwedenISOLDE-CERN, Geneva, SwitzerlandUniversidad Complutense, Madrid, SpainIEM-CSIC, Madrid, SpainIReS, Strasbourg, FranceASINS, Świerk, PolandK.U. Leuven, IKS, Leuven, BelgiumIPNO, Orsay, FranceUniversity of Liverpool, Liverpool, UKLund University, Lund, Sweden
Århus University, Århus, DenmarkOslo University, Oslo, NorwayJYFL, Jyväskylä, FinlandWarsaw University, Warsaw, PolandRIKEN, Wako, JapanRez, Czech RepublicUniversidad Autónoma, Madrid, SpainUniversity of Valencia, Valencia, Spain.Technical University, Munich, Germany