Excitation and decay of Isoscalar Giant Dipole Resonance

• Introduction on Giant Resonance

• A schematic model of GR

• Excitation of ISGDR in 58Ni (`) reaction

• Experimental details

• Data Analysis

• Results and discussions

• Summary and conclusions

A Schematic Model of GR:

The H0 to denote the Hamiltonian operator of a nucleon in the central potential of the single particle shell model. In the transition of the particle from a full shell to the one above , we must also take the particle-hole interaction into account ; the Hamiltonian operator then be written as

The collective excitations appear just because of the mixing generated by this particle-hole interactions V.

Giant Resonance: Coherent vibration of nucleons in a nucleus.

Nucleus Many body system with a finite size

Vibration Multi-pole expansion with r, Ylm,

L=0: Monopole

L=1: Dipole

L=2: Quadrupole

L=3: Octupole

S=0, T=0 S=0, T=1

ISGMR

S=0, T=1

IVGMRIAS

S=1, T=1

GTR IVSMGR

S=1, T=1

LEOR, HEOR

r2Y0 Y0

ISGQR IVGQR

ISGDR IVGDR SDR

r2Y0 Y0 r2Y0

r3Y1 rY1r3Y1 rY1

r3Y1

r2Y2 r2Y2 r2Y2

rY3, r3Y3

Isoscalar Excitation Modes of Nuclear Resonance

2

2

)25/27(

7

3

rm

KE

rm

KE

FAISGDR

AISGMR

0

2

22 )/(

9

d

AEdKnm

Giant Resonance: Coherent vibration of nucleons in a nucleous.Resonances due to imcompressibility :ISGMR, ISGDR

Nuclear matter

29.5 MeV

c.m.

0 2 4 6 8 10 12

10-2

10-1

100

101

102

ISGMR, ISGDR

TAMU(2000)KVI (1977)

Large instrumental background!励起の弱い ISGDR を議論するには不十分。

D.H. Youngblood et al., RIKEN Rev. 23, 159(1999)

Y.-W. Lui et al., PRC 61, 067307 (2001)

Measurement Details

• 386 MeV @RCNP 58Ni, 90Zr, 116Sn, Sm, 208Pb

• 0-13 deg (Angular range)

• Elastic scattering :-3.5-25 deg range.

NucleusAngles

(degree)Excitation energy(MeV)

58Ni 0-13 10-35-52

90Zr 0-13 10-35

116Sn 0-13 10-35

Sm 0-13 10-35

208Pb 0-13 10-35

RCNP

E=386 MeVE = 250 keV@FWHM

Halo free beam~10 counts/ 1nA@ empty target, 0degs.

.

• RCNP facility K=400 MeV ring cyclotron Grand Raiden spectrometer• Beam ：

– 4 He++, 386 MeV• Target:

58Ni foil 5.8mg/cm2

GRAND RAIDEN SPECTROMETER

VDC Y-positionVDC Y-position

Instrumental Background

Excitation Energy Spectra at 0Excitation Energy Spectra at 0oo Angular Distribution Angular Distribution

Typical Spectra

Excitation Energy Spectrum

Multipole decomposition analysis (MDA)

• DWBA 計算　・・・　 Ptolemy• Folding Model

DWBA Formalism:

Transition Potential:

Transition density

• ISGMR G.R.Satchler, Nucl, Phys, A472 (1987) 215

• ISGDR M.N.Harakeh, Phys. Rev. C23 (1981) 2329

• Other modes Bohr-Mottelson(BM) model

58 Ni

SN1987ATransverse flow

CONCLUSIONS. A two component ISGDR strength distribution has been obtained for the first time in 58Ni

ISGDR strength distribution is in excellent agreement with recent QRPA predictions.

The value of incompressibility of infinite nuclear matter( Knm ) is 217 MeV as obtained from global systematic of present study.