Half-life measurement of isomeric states in A = 25 & 26

D. Nishimura1,

p. /26

Contents

2

•Background & Motivation•Nucleosynthesis of rp-process

•Experiment•Facility (NIRS-HIMAC, SB2 beam line)

•Experimental Setup(γ-ray detection system)

•Results & Discussion•γ-ray energy spectra and decay curves

•Eγ, T1/2 and Level scheme

•Transition probabilities and comparison with shell model calc.

•Summary

Background & Motivation

p. /26

25Si & 26P

4

⑧

②

⑳

proton neutron

1s1/2

1p3/2

1p1/2

2s1/2

1d3/2

1d5/2

25Si + p26P

3+

40(5)

5/2+

?

0

[2] β decay of 25Si & 26P and IAS-ΔE assumed: J.-C.Thomas et al., Eur. Phys. J. A 21, 419 (2004).[1] Improved Kelson-Garvey mass relation: J. Tian et al., Phys, Rev. C 87 014313 (2013)

β+

β+

Possibility of new rp-process path

[3] AME2003 mass evaluation: G.Audi, A. H.Wapstra and C.Thibault, Nucl. Phys. A729, 337 (2003).

–119 ± 6 [1] 0 ± 90 [2] 140 ± 200 [3]

?

Nuclear chart Convensional configuration of 26P

Level scheme

14

15

11

{Sp =

Motivation

investigation of 25mSi & 26mP

? 164.1(1)Jπ Ex

N = Z

p. /26

(1) Nuclear Synthesis of rp-process

5

R.K.Wallace and E. Woolsey, Astro. J. 45 389 (1981).

T ~ 108-9K (= 10-100 keV)

25Si

26P

27S

26Si 27Si 28Si 29Si 30Si

27P 28P 31P29P 30P

24Al 25Al 26Al 27Al 29Al28Al

28S 29S 32S30S 31S

22Si 23Si 24Si

23Al

21Mg 22Mg 23Mg 24Mg 25Mg 26Mg20Mg 27Mg 28Mg

20Na 23Na21Na 22Na

31Cl 32Cl 33Cl

19Na 24Na 25Na 26Na 27Na

?

? ?

??

A. Parikh, et al., Phys. Rev. C 79, 045802 (2009).

The low-lying excited states can affect the reaction rate.

N = 11

p. /26

rp-process in N = 11 isotones

6

25Si26P

3+

24Al

4+

1+ 426

5/2+

27S

g.s.Sp =3414

Sp = 140 keV?

Sp = 1200 keV?

23Mg

3/2+ g.s.Sp =1863 keV

(p,γ)

(p,γ)

(p,γ)?(p,γ)?

? 40

1963

815

2373

2606

?

?

?

?

H. Herndl et al., Phys. Rev. C 52, 1078 (1995).

T ~ 108-9K (= 10-100 keV)

The low-lying excited states can affect the reaction rate.

?

p. /26

rp-process in N = 11 isotones

7

25Si26P

3+

24Al

4+

1+ 426

5/2+

27S

g.s.Sp =3414

Sp = 140 keV?

Sp = 1200 keV?

23Mg

3/2+ g.s.Sp =1863 keV

(p,γ)

(p,γ)

(p,γ)?(p,γ)?

? 40

1963

815

2373

2606

?

?

?

?

H. Herndl et al., Phys. Rev. C 52, 1078 (1995).

T ~ 108-9K (= 10-100 keV)

The low-lying excited states can affect the reaction rate.

?

Determine Eγ, T1/2 and Jπ

Experiment

p. /26

SB2 beam line in NIRS-HIMAC

9

28Si 300 MeV/u

4.0 × 108 particle/pulse

(CH2)n 20 mmt

0.5 mm

5.1 mm

Experimental

area

Bρ1 = 4.083 Tm

2nd

Bρ2 = 3.701 Tm

193 MeV/u

TOF

ΔE

28Si + CH2 → 25Si + X→ 26P + X

–3n

–3n, +1p

28Si

NIRS-Heavy Ion Medical Accelerator in Chiba (Japan)

SecondaryBeamline

Synchrotron for canser therapy

p. /26

25Si26P

TOF (ns)

ΔE

(M

eV)

Particle ID prot

Production of 25Si & 26P

10

Momentum distribution

101

102

103

104

105

106

Yie

ld (p

pp/T

m)

4.54.44.34.24.14.03.9Βρ1 (Tm)

26P(exp)26P(LISE++)25Si(exp.)25Si(LISE++)

Δp/p = ±1%

Countingrate (ppp)

Purity(％)

Total(counts) Ref.

26P 44 3.6 2.0×105

25Si 850 70 3.9×106

26P 100 74 – MSU26P 65 87 – GANIL

28Si(300MeV/u,0.06pnA) + CH2 →

36Ar(150MeV/u,75pnA) + 9Be →

36Ar(95MeV/u,110pnA) + 9Be →

HIMAC

MSU; M.B. Bennett, et al., PRL 111, 232503 (2013).GANIL; J.-C.Thomas et al., Eur. Phys. J. A 21, 419 (2004).

p. /26

Energy Resolution @662keV

Time Resolution

Distance to stopper Solid Angle /4π

HPGe 3.6 keV ~80 ns 40 mm 10%

LaBr(Ce) 20 keV 2 ns 53 mm 2.5% × 4 = 10%

NaI(Tl) 45 keV 5 ns 62 mm 20%

Experimental setup at F3

11

LaBr3(Ce) x 4

NaI(Tl) x 1

HPGe x 1Active stopperPPAC

PS GSO

Al degraders(9 mm)

(50 mmφ x 20 mmt)

(38 mmφ x 38 mmt)

(127 mmφ x 70 mmt)

Shield(Pb+Cu+Al)

40 mm

PS (1+3+1) mm

Properties of γ-ray detectors

p. /26

Energy Resolution @662keV

Time Resolution

Distance to stopper Solid Angle /4π

HPGe 3.6 keV ~80 ns 40 mm 10%

LaBr(Ce) 20 keV 2 ns 53 mm 2.5% × 4 = 10%

NaI(Tl) 45 keV 5 ns 62 mm 20%

Experimental setup at F3

12

LaBr3(Ce) x 4

NaI(Tl) x 1

HPGe x 1Active stopperPPAC

PS GSO

Al degraders(9 mm)

(50 mmφ x 20 mmt)

(38 mmφ x 38 mmt)

(127 mmφ x 70 mmt)

Shield(Pb+Cu+Al)

40 mm

PS (1+3+1) mm

Properties of γ-ray detectors

LaBr3(Ce)NaI(Tl)

HPGe

Results & Discussion

p. /26

How to Search Isomeric States

14

0t γ

– t

0

Eγ (keV)

Prompt γ rays and X rays

Isomeric γ rays

t0: time of ion implantation

tγ: time of γ-ray detection

t0

~~~

tγ Eγ

p. /26

0 50 100 150 200 250 300

0

200

400

600

800

1000

1

10

210

0 50 100 150 200 250 3000

200

400

600

800

1000

1

10

210

0 50 100 150 200 250 300

0

200

400

600

800

1000

1

10

210

Energy-Timing correlations of γ rays

15

HPGe

LaBr3(Ce)

NaI(Tl)25Si NaI(Tl)

0 50 100 150 200 250 300

0

200

400

600

800

1000

1

10

210

0 50 100 150 200 250 3000

200

400

600

800

1000

1

10

210

310

0 50 100 150 200 250 300

0

200

400

600

800

1000

1

10

210

310

26P25Si

100 200 3000

200

400

600

800

1000

0

200

400

600

800

1000

0

200

400

600

800

1000

0

200

400

600

800

1000

0

200

400

600

800

1000

0

200

400

600

800

1000

0

t γ –

t0

(ns)

Eγ (keV)100 200 3000

26P25Si

26P25Si

p. /26

Energy (keV)0 50 100 150 200 250 300

(cou

nts/0

.5 k

eV)

N

50

100

150

200

250

300

Time (nsec)0 200 400 600 800 1000

(cou

nts/4

ns)

N1

10

210

310

γ-ray Energy & Timing Spectra

16

26P

Eγ = 163.7(2) keV T1/2 = 106(4) nsc.f. 164.1(1) keV of our previous exp. c.f. 120(9) ns of our previous exp.

by LaBr3(Ce)by HPGe

p. /26

Energy (keV)0 50 100 150 200 250 300

(cou

nts/0

.5 k

eV)

N

50

100

150

200

250

300

Time (nsec)0 200 400 600 800 1000

(cou

nts/4

ns)

N

1

10

210

310

γ-ray Energy & Decay Time Spectra

17

Eγ = 44.9(2) keV T1/2 = 43.2(8) nsc.f. 40.0(50) keV

25 times precession improved!

by LaBr3(Ce)by HPGe

25Si

New!

p. /26

Weiskoppf estimation

18

26P26P 25Si25Siα W.u. α W.u.

E1 0.00221 1.68×10–6 0.115 1.82×10–4

M1 0.00142 4.81×10–5 0.0302 5.49×10–3

E2 0.0191 9.89×100 2.99 4.16×103

M2 0.00993 2.85×102 0.662 2.78×105

E3 0.139 8.07×107 65.2 3.12×1010

M3 0.0687 2.46×109 14.4 3.74×1012

α : internal conversion coefficients

BRICC code: T. Kibedi, et al., NIM A 589. 202(2008).

p. /26

Weiskoppf estimation

19

26P26P 25Si25Siα W.u. α W.u.

E1 0.00221 1.68×10–6 0.115 1.82×10–4

M1 0.00142 4.81×10–5 0.0302 5.49×10–3

E2 0.0191 9.89×100 2.99 4.16×103

M2 0.00993 2.85×102 0.662 2.78×105

E3 0.139 8.07×107 65.2 3.12×1010

M3 0.0687 2.46×109 14.4 3.74×1012

α : internal conversion coefficients

BRICC code: T. Kibedi, et al., NIM A 589. 202(2008).

Since B(M1) of 8.61×10–5 μN2 for 26P is extremely hindered,

M1 transition can be probably rejected.

Since there are no negative parity states, E1 transition can be rejected.

p. /26

Comparison with Shell Model (26P)

20

26Na 26P3+ 3+

1+

(1+)

82.5

163.8

E2E2

exp. USD USDA USDB

26P 45.3 31.2 32.3 24.026Na 31.3* 39.3 38.1 31.3

B(E2)↓ values (in units of e2 fm4).

* T1/2 =4.16(25)μs, α = 0.137 is used.

B. Siebeck et al., Phys. Rev. C 91, 014311 (2015).

2+233.3

2+406.5

USD1+

3+1822+187

2+413

USDA3+

1+77

2+149

2+416

USDB3+

1+4

2+108

2+325

00.0

W.A. Richter et al., Phys. Rev. C 78, 064302 (2008).

Exp. Theory

ep = 1.36 & en = 0.45 are usedD. Nishimura et al., EPJ Web of Conf. 66, 02072 (2014).

p. /2621

25Na 25Si5/2+

5/2+

3/2+

(3/2+)0

00

44.9(2)89.5

M1(+E2)

exp. USD USDA USDB25Si 0.0098(3) 0.0490 0.0292 0.0302

25Na 0.0108(6) 0.0703 0.0444 0.0439

B(M1)↓ values in units of μN2

W.A. Richter et al., Phys. Rev. C 78, 064302 (2008).

5/2+

3/2+113

USD USDA USDB

1/2+1159

5/2+

3/2+

0

181

1/2+1029

5/2+

3/2+

0

114

1/2+9661/2+1069815

Comparison with Shell Model (25Si)

assuming mixing ratio δ =0.

?

M1(+E2)

25Si 25Na

theory (μN)

(μN)

M(M1) = √ (2Ji +1) B(M1)

p. /26

Configuration Mixing

22

26P

25Si

by using USDA

50403020100

Population (%)

[060] [030][060] [021][060] [120][060] [111][060] [012][060] [210][051] [030][051] [021][051] [120][150] [030][150] [021][150] [120][042] [030][042] [021][141] [030][141] [021][141] [120][240] [030][240] [021][132] [030][231] [030][222] [030]

25Si 3/2+ (i.s.)

50403020100

Population (%)

[060] [030][060] [021][060] [120][060] [111][060] [012][060] [210][051] [030][051] [021][051] [120][150] [030][150] [021][150] [120][042] [030][042] [021][141] [030][141] [021][141] [120][240] [030][240] [021][132] [030][231] [030][222] [030]

25Si 5/2+ (g.s.)

π[d3/2 d5/2 s1/2] ν[d3/2 d5/2 s1/2]

50403020100

Population(%)

[061] [030][061] [021][061] [120][061] [012] [061] [111][061] [210][160] [030][160] [021][160] [120][052] [030][052] [021][151] [030][151] [021][151] [120][250] [030][250] [021][250] [120][142] [030][241] [030][241] [021][340] [030]

26P 1+ state(i.s.)

50403020100

Population (%)

[061] [030][061] [021][061] [120][061] [012] [061] [111][061] [210][160] [030][160] [021][160] [120][052] [030][052] [021][151] [030][151] [021][151] [120][250] [030][250] [021][250] [120][142] [030][241] [030][241] [021][340] [030]

26P 3+ (g.s.)

0 10 20 30 40 50 10 20 30 40 50

5/2+(g.s.)

1+(i.s.)3+(g.s.)

3/2+(i.s.)

<πs1/2> = 0.76<πs1/2> = 1.09

3+(g.s.) 1+(i.s.)

5/2+(g.s.) 0.614 0.291

3/2+(i.s.) 0.003 0.248

25Si26P

Spectroscopic factorsC2S

<πs1/2> = 0.63<πs1/2> = 0.52

26P

25Si

45 3/2+

5/2+0

0

164 1+

3+

p. /26

Summary

23

•Proton-rich nuclei 25Si and 26P have attracted much interest since they are related to nuclear synthesis of rp-process.

•The low-lying isomeric states in 25Si and 26P have been

investigated by using γ-ray spectroscopy at NIRS-HIMAC.

•The γ-ray energy and half-life for 25Si and 26P are determined to be

Eγ = 44.9(2) keV, Eγ = 163.8(2) keV

T1/2 = 43.0(6) ns, T1/2 = 104(3) ns

•M1 for 25Si and E2 for 26P transitions are suggested by calculating

the transition probabilities with the above Eγ and T1/2. Therefore,

Jπ = 3/2+ and Jπ = 1+ are expected for their isomeric states.

•In order to calculate NA<συ>, theoretical support and precise mass measurement

are desiable.

25Na 25Si5/2+

5/2+

3/2+

(3/2+)0

0

44.9(2)89.5

M1(+E2)

26Na 26P3+ 3+

1+

(1+)

82.5

163.8

E2E2

0.0

M1(+E2)

Backups

p. /26

E2 matrix element in sd shell

25

0

expe

rimen

t (e

fm2 )

ep = 1.36en = 0.45

Mp = √ (2Ji +1) B(E2)

An(TZ = –2) = Ap(TZ = +2)

Assuming that shell model results of

Mp = ep Ap + en An

We can solve ep and en

Ap = 4.74 and An = 5.95

ep = 0.19en = 1.81

← very strange !!

26P

26Na

Shell model does not perfectly reproduce the isospin symmetry of B(E2) in 26P & 26Na pair.

W.A. Richter et al., Phys. Rev. C 78, 064302 (2008).

{

Matrix element

{

p. /26

Results of Eγ & T1/2

26

Eγ(keV) T1/2(ns)

HPGe 163.7(02) 103(8)

LaBr3(Ce) 164.1(10) 106(4)

NaI(Tl) 163.8(10) 102(4)

Ave. 163.8(2) 104(3)

25Si26P

Eγ(keV) T1/2(ns)

HPGe 44.9(02) 42.3(30)

LaBr3(Ce) 42.0(20) 43.2(08)

NaI(Tl) 44.8(20) 42.8(08)

Ave. 44.9(2) 43.0(6)

c.f. 40.0(50) keV

p. /26

(2) Candidate for proton halo

c.f. 8B = 7Be + p (1p3/2) S1p = 137 keV 17Ne = 15O + 2p (2s1/2) S2p = 943 keV

c.f. Shell model: B.A. Brown & P.G. Hansen Phys. Lett. B 381 391 (1996).

Γ (MeV/c) σ–1p (mb)

9Be(26P, 25Si)X 137(33) 72(13)9Be(27P, 26Si)X 116(8) 74(11)9Be(28P, 27Si)X 143(14) 70(11)

A. Navin et al., Phys. Rev. Lett. 81 5089 (1998).

Y.-J Liang et al., Chin. Phys. Lett. 26, 032102 (2009).

ρ(r) deduced by RMF calc.

25Sip

P// distribution

26P = 25Si + p (2s1/2)

?

–119 ± 6 keV [1] 0 ± 90 keV [2] 140 ± 200 keV [3]

{Sp =

Theory

Exper

imen

t

largenarrow

large tail

26P =

27

p. /26

Check of Direct Proton Emission

28

25Si5/2+

26P0 3+

0

45

164 104 ns

43 ns

Iγ(44)/Iγ(164) < 5%.

p?

0 50 100 150 200 250 3000

200

400

600

800

1000

1

10

21026P

200

400

600

800

1000

0100 200 3000

We did not observe 44-keV & 104-ns γ rays in 26P.

by LaBr3(Ce)

E-T correlation

No γ rays