the lifetime measurement of first 2 + state in 174 os with labr 3 (ce)

The Lifetime The Lifetime Measurement of First 2Measurement of First 2++

State in State in 174174Os with Os with LaBrLaBr33(Ce)(Ce)

李聪博 1,2 等指导教师：吴晓光 1 ，李险峰 2

1 中国原子能科学研究院2 吉林大学

2012-4-13 浙江湖州

CONTENTSCONTENTS IntroductionIntroductionLaBrLaBr33:Ce Crystals:Ce Crystals and Testand TestExperimental Electronics Experimental Electronics and Data analysis methodand Data analysis method

Off-line Test with Off-line Test with 152152Eu Eu In-beam ExperimentsIn-beam ExperimentsConclusionsConclusions

IntroductionIntroduction

A Large error bar

Neutron mid-shell

174Os

Os

IntroductionIntroduction1. Recoil distance method (RDM) with

Plunger devices. (ps - ~1ns)2. Triple-βγγ (t) coincidence method using

a mix of Ge, plastic, BaF2 or LaBr3(Ce) in β decay experiment. (>several Ps) H. Mach et al, Nucl. Instrum. Meth. A 280, 49 (1989).

3. A new experimental method Triple-γγγ (t) with LaBr3(Ce) and Ge in-beam experiments. (>several Ps)

174Os(21+) with lifetime 505(60) ps

(RDM). J. Gascon et al., Nucl. Phys. A 470, 230 (1987).

N. Mărginean, et al., Eur.Phys.J.A 46,329(2010)

LaBrLaBr33:Ce Crystals:Ce Crystals and and TestTest

crystals Dendity（ gcm-3）

Light yield（ ph/keV）

Decay time（ n

s）

maximum emission（ nm）

Energy resolution（ %） 662k

eV

NaI:Tl 3.67 41 230 410 5.6CsI:Na 4.51 40 630 420 7.4CsI:Na 4.51 66 1000x800/6 550 6.6LaCl3:Ce 3.79 49 28 350 3.8LaBr3:Ce 5.0 63 16 380 2.8BGO 7.1 9 300 480 9.0LSO 7.4 26 40 420 7.9GSO 6.7 8 60 440 7.8YAP 5.5 21 30 350 4.3BaF2 4.9 2 0.8 225 10

LaBr3:Ce CrystalsLaBr3:Ce Crystals and and TestTest

CrystalscharacteristicsVolume: Four 30 × 30mm

Three 1 × 1 inch cylinder

LaBrLaBr33:Ce Crystals:Ce Crystals and and TestTest

Energy Resolution

LaBrLaBr33:Ce Crystals:Ce Crystals and and TestTest

Time Resolution

22Na

Experimental Electronics and Experimental Electronics and Data analysis methodData analysis method

Experimental Electronics Experimental Electronics and Data analysis and Data analysis

methodmethod1. FWHM

Sloping method

2. FWHM

H. Mach, R.L. Gill and M.Moszyinski, Nucl. Instrum. Meth. A 280, 49 (1989).

Off-line Test with Off-line Test with 152152EuEu

Off-line Test with Off-line Test with 152152EuEu

Deconvolution Fitting

T1/2=1.42(2)ns

1.39（ 3） ns

In-beam ExperimentsIn-beam Experiments

28 150 174 4Si Sm Os n

35 144 176 1 2Cl Sm Pt p n

37 144 178 1 2Cl Sm Pt p n

In-beam ExperimentsIn-beam Experiments28 150 174 4Si Sm Os n

Cascade

In-beam ExperimentsIn-beam Experiments

Beams: 140 MeV

28Si

Target: 0.9mg/cm2

152Sm rolled onto

a12.5mg/cm2 Pb

backing

10 HPGe-BGO , 2

Planar HPGe and 7

LaBr3(Ce)

In-beam ExperimentsIn-beam Experiments

J.L. DURELL et al. Phys. Letter. B115 367(1982)

In-beam ExperimentsIn-beam Experiments

508(16)ps

In-beam ExperimentsIn-beam Experiments

Jing-ye Zhang et al., Phys. Rev. C 73, 037301 (2006)

A subshellstructure in the evolution of W and Os isotopic chains.

4A large increase

In-beam ExperimentsIn-beam Experiments

M. Rudigier et al., Nucl. Phys. A 847, 89 (2010).

In-beam Experiments

N.V. Zamfir et al. Phys. Letter. B357 515(1995)

4

P.Moller,J.R.Nix,W.D.Myers,W.J.Swiatecki,At.DataNucl.DataTables59(1995)185–381.

20 2 2 4~ (1 0.3604 0.9672 )Q

22

1 1 20( 2 : 2 0 ) ( ).16

eB E Q

241 1 1 1

4

( 0)( 2 : 2 0 ) ( 2 : 2 0 ).( )

( 0)Q

QB E B E

Q

In-beam ExperimentsIn-beam Experiments

In-beam Experiments

Suggested as +0.1174

+0.145

M. Rudigier et al., Nucl. Phys. A 847, 89 (2010).

P.Moller,J.R.Nix,W.D.Myers,W.J.Swiatecki,At.DataNucl.DataTables59(1995)185–381.

ConclusionsConclusionsThe lifetime of the first excited 2+ state in 174Os has been remeasured in fast time experiment and determined to be a greater accuracy, to be 508(16)ps. A deviation of the B(E2) value systematics in 174Os may hint a nuclear structure change, resulting a large increase in hexadecapole deformation (with +0.145).These explanations, from phenomenology at least, modify the expected trends. Other explanations, especially with microscopic model calculations, are needed.

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