Isospin impurity of the Isobaric Analogue State of super-allowed beta decay

Isospin impurity of the Isobaric Analogue State of super-allowed beta decay

• experimental technique• isospin impurity determination

Bertram Blank, CEN Bordeaux-Gradignan ESNT, Saclay, April, 26-29, 2011

The idea:The idea:

T, Tz- 1

T-3/2, Tz-3/2

T, Tz

Super-allowed decay

Proton emission

T - 1, Tz- 1

Gamma decay

The idea:The idea:

52Co: T=2, Tz=-1

51Fe: T=1/2, Tz=-1/2

52Ni: T=2, Tz=-2

Super-allowed decay

Proton emission:T=1/2, Tz = -1/2

T= ½ + ½ T = 1, Tz = -1 T = 2

Gamma decay

Can one determine the isospin impurity of the IAS?

Calcium: 37,36Ca

Titanium: 41,40,39Ti

Vanadium:43V

Chromium:45,44,43,42Cr

Manganese :47,46Mn

Iron:49,48,47,46,45Fe

Cobalt:51,50Co

Nickel:53,52,51,50,49,48Ni

Copper: 55Cu Zinc: 56,55,54Zn

Proton-rich nuclei in the region of Ca to NiProton-rich nuclei in the region of Ca to Ni

Mass region (20 Z 28 et Tz -3/2) 5 experiments at GANIL 23 isotopes studied (39Ti au 53Ni)

Mass region (20 Z 28 et Tz -3/2) 5 experiments at GANIL 23 isotopes studied (39Ti au 53Ni)

Primary beam:58Ni @ 75 MeV/Aintensity: 3 - 4 Ae

SISSI target:natNi 200 mg/cm2

spectrometer LISE3 :degrader Be (50 m)Wien filter

detectionsetup

silicon telescopeidentification ofimplanted fragments

DSSSD (X-Y): 2 x 16 x 3 mm

- veto for light particles- residual energy, x-y position- energy loss

- time of flight: micro-channel plate detectors RF cyclotron

Identification projectile fragmentsIdentification projectile fragments

7 to 8 identification parameters

Proton and gamma branching ratios and energiesProton and gamma branching ratios and energies

41Ti

T

B1 B2

A

41Ti 41Ti

Rad

ioac

tivi

ty o

f 41

Ti

Rad

ioac

tivi

ty o

f 49

Fe

Correlation time

Protons

41TiContaminant from 49Fe and 45Cr

Background subtraction for raysBackground subtraction for rays

49Fe 49Fe

Before After

Contaminants

Decay of 49Fe

Decay of 49Fe

C. Dossat et al., NPA 792 (2007) 18

Spectroscopy of 52NiSpectroscopy of 52Ni

T1/2 = (40.8 ± 0.2) ms

Pp = (31.4 ± 1.5) %

• Ep = (2815 ± 23) keV • Ip = (0.9 ± 0.4) %

• Ep = (1349 ± 10) keV • Ip = (9.4 ± 1.3) %

• Ep = (1057 ± 11) keV • Ip = (2.9 ± 0.3) %

C. Dossat et al., NPA 792 (2007) 18

Spectroscopy of 48FeSpectroscopy of 48Fe

T1/2 = (40.8 ± 0.2) ms

Pp = (31.4 ± 1.5) %

• Ep = (1013 ± 12) keV • Ip = (1.8 ± 0.3) %

• Ep = (2000-3000) keV • Ip = (1.4 ± 0.5) %

• Ep = (1500-1900) keV • Ip = (2.0 ± 0.4) %

C. Dossat et al., NPA 792 (2007) 18

Isotope

Half-life (ms)Total proton branching ratio

(%)Mass excess via IMME

37Ca 181.7 ± 3.6 72.2(43) -36Ca 100.1 ± 2.3 51.2(10) -41Ti 82.6 ± 0.5 91.1 (6) -15.717(7)40Ti 52.4 ± 0.3 95.8 (13) -9.06(8)39Ti 28.5 ± 0.9 93.7(28) -43V 79.3 ± 2.4 < 2.5 -

45Cr 60.9 ± 0.4 34.4 (8) -19.49 (3)44Cr 42.8 ± 0.8 14.0 (9) -13.64 (2)43Cr 21.1 ± 0.4 92.5 (28) -1.92(6)42Cr 13.3 ± 1.0 94.4(50) -

47Mn 88.0 ± 1.3 < 1.7 -46Mn 36.2 ± 0.4 57.0 (8) -12.49 (3)49Fe 64.7 ± 0.3 56.7 (4) -24.67 (2)48Fe 45.3 ± 0.6 15.9 (6) -18.07 (5)47Fe 21.9 ± 0.2 88.4 (9) -7.08 (4) 46Fe 13.0 ± 2.0 78.7 (38) 0.76 (10)51Co 68.8 ± 1.9 < 3.2 -50Co 38.8 ± 0.2 70.5 (7) -17.59 (4)53Ni 55.2 ± 0.7 23.4 (10) -29.39 (4)52Ni 40.8 ± 0.2 31.4 (15) -22.64 (3)51Ni 23.8 ± 0.2 87.2 (8) -11.93 (7)50Ni 18.5 ± 1.2 86.7(39) -4.14 (3)49Ni 7.5 ± 1.0 83.4 (132) -

55Cu 27.0 ± 8.0 15.0 (43) -56Zn 30.0 ± 1.7 86.9(49) -55Zn 19.8 ± 1.3 91.0(51) -

Proton emission from the IAS is isospin forbidden

Comparison of , and of for IAS :

• 48Fe : = 2.1 % - = 30% = 42 %• 52Ni : = 10 % - = 38% = 64 %

Determination of isospin impurities with these experimental data:

•

• (experimental, theory)

• ’p : Coulomb and centrifugal barrier penetration

• Sp = 1

Isospin impuritiesIsospin impurities

IASpI IAS

βthI

IASpI IAS

βthIIASpI IAS

βthIIASIIASI

ip'

iIASp

IAS

IS I I

I

pp

IAS

IASp

p'i I

I

S I

p

X IASp

IASβth

IASγ III

IASI

Isospin impurity: example of 48FeIsospin impurity: example of 48Fe

= 2.1 %

= 42 %

II = 0.52 %

Measured energies (keV)

Predicted energies (keV)

EIAS 3037 (10) 2979

E (IAS – 1+) 2631 (1) 2458

E

(2+ - ground state)313.0 (5) 233

IASβthI

IASpI

W.A. Richter, B.A. Brown

IAS Shell model (48Mn)

Isospin impurity: example of 52NiIsospin impurity: example of 52Ni

= 10 %

= 64 %

II = 19 %

Measured energy (keV)

Predicted energy (keV)

EIAS 2931 (10) 2796

Shell model (52Co)

IASpI

IASβthI

IAS

W.A. Richter, B.A. Brown

neighboring nuclei: surprising…

however: shell-model study :

II(36Ca) = 0.4 %, II (40Ti) = 17.3 % (Theory Jyväskylä in sd shell)

similar treatment possible for many other nuclei: 45,44Cr, 46Mn, 49Fe, 53,51Ni….

II(48Fe) = 0.52 %, II (52Ni) = 19 %

Isospin impurity of IASIsospin impurity of IAS

B.A. Brown, N. Smirnova….