Excitation of M1 states in 58Ni and 60Ni by 65 MeV polarized proton inelastic scattering

Nuclear Physics @ North-Holland

A454 (1986) 237-251 Publishing Company

EXCITATION OF Ml STATES IN %Ni AND @Ni BY 65 MeV POLARIZED PROTON INELASTIC SCATTERING K. HOSONO,

M. FUJIWARA, H. IKEGAMI, M. KONDO, N. MATSUOKA, T. SAITO and T. YAMAZAKI

Research Center for Nuclear Physics, Osaka University, Ibaraki, Osaka 567, Japan S. MATSUKI Cyclotron

Laboratory, Institute for Chemical Research, Kyoto University, Kyoto 606, .fQpQ?I K. OGINO Department of Nuclear Engineering, Kyoto University, Kyoto 606, Japan S. KATO

Laboratory of Nuclear Studies, Faculty of Science, Osaka University, Toyonaka, Osaka 560, Japan T. YANAGIHARA* Department of Physics, Hiroshima University, Hiroshima 730, Japan Received 20 December 1985 (Revised 27 January 1986)

Abstract: We studied the l+ states in s8Ni and “Ni by using the ‘*Ni(p, p’)s8Ni and 6oNi(p, P’)~‘N~ reactions at 65 MeV with high resolution, in order to search for the fragmentation of the l+ states at excitation energies of E, = 7- 11 MeV. From the similarity in experimental shapes of both cross sections and analyzing powers for the well-known l+ states and from comparison with microscopic DWBA calculations under the assumptions of pure (f;,$fSj2) and ~(pr,~p,,~) configurations, four of the l+ states of a states in ‘*Ni and one state in 60Ni have been identified as the candidates (f&f,,,) or ~(p~,~p,,~) configuration in the Ml giant resonance region of E, = 7-10 MeV, though the strengths are very weak.

E

NUCLEAR REACTIONS ‘*Ni, 60Ni(polarized p, p’). E = 65 MeV; measured analyzing power A( 0). 5*Ni, 60Ni levels deduced Ml character. Microscopic analysis.

a( 0), DWBA

1. Introduction The particle-hole model predicts the existence of spin-flip giant Ml states as a systematic feature of nuclei. Charge exchange (p, n) reactions performed on many targets ranging from 40Ca to *‘*Pb have shown the excitation of the giant GamowTeller resonance ‘22), which is the antianalog of the Ml resonance. In the last several years, experimental investigations were carried out in search for the Ml giant l

Present

address:

Sanyo

Electric

Co., Ltd. 237

K. Hosono et al. / Ml states

238

resonance. energies

In La, Ce and of about

Pr, broad

9 MeV in electron

Ml resonances inelastic

were observed

scattering

3*4). There

at excitation is also some

support for this from a r4’Ce( y, n) reaction ‘). Recently, in a series of seventeen nuclei ranging from 51V to 14’Ce, broad structures have been observed by inelastic scattering of 200 MeV protons at forward angles “). The broad structures have a width of 1.7 f 0.2 MeV at an excitation energy of E, = 8 - 10 MeV, which are nearly mass independent and show an AL = 0 angular distribution which has been interpreted as the Ml giant resonances. Similar features have been observed in “Zr(p, p’)“Zr inelastic scattering by 200 MeV protons at TRIUMF ‘). On the other hand, the results of the high resolution study of electron inelastic scattering 8,9) on 90Zr and 14’Ce indicate that the level structure in the 8-10 MeV excitation energy region is complicated, and that the bulk of the strength observed in this region is of M2 character. By searching for peaks which increase with decreasing incident electron energy, three l+ states have been identified. The (7, 7’) experiment lo), the proton r’*‘*) and the electron r3) inelastic scatterings have also revealed only a few narrow Ml states in the 7-9 MeV energy region. All of these results appear to be in conflict. We expect to see the fragmented structure near 9 MeV excitation energy by a high resolution experiment. The purpose of this work, therefore, is to search for the fragmented l+ states at the excitation energy of 7 to 11 MeV in “Ni and 60Ni and to identify, if possible, the configuration of the wave function. We carried out a high resolution (p, p’) experiment with 65 MeV polarized protons, which is high enough to ensure the simple direct process without complicated reaction mechanisms such as two-step processes r4). An effect which is invisible in the angular distributions of the cross sections may be apparent in those of the analyzing powers. The 2.903 MeV and the 5.166 MeV states in ‘*Ni have been assigned as the l+ states of the (p3,2f5,2) and the (~~,~pr,~) configuration respectively I*). The 10.67 MeV state in 58Ni and 11.86 MeV state in “Ni are considered as the (f;:2f5,2) isovector It state. Among the l+ states in medium nuclei, the 10.22 MeV, l+ state in 48Ca is believed to be the state with its main component of the (f;jzf5,J configuration. The angular distributions of these known l+ states have been also observed as standard shapes for the identification of the l+ states. The experimental procedures and the results are presented in sects. 2 and 3, respectively. The DWBA calculations of the measured cross sections and the analyzing powers, the distribution of the Ml states, the configuration of the wave function are described in sect. 4 along with a discussion. In the last section, we summarize the conclusions.

2. Experiment A 65 MeV polarized proton protons from an atomic-beam

beam was used for the experiment. The polarized type polarized ion source were accelerated by the

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AVF cyclotron at Research Center for Nuclear Physics, Osaka University (RCNP). The measurements were carried out using the spectrograph RAIDEN I’). The beam polarization was monitored by a “C polarimeter for ten seconds after every one and one-half minute measurement with the spectrograph. A polarized proton current of up to 50 nA was delivered onto the target with polarization of about 80%. The focal plane detector 16) consists of a position-sensitive resistive-wire proportional counter followed by dual proportional counters ( AE, and AEJ and a plastic counter (E). They were operated in a fourfold coincident mode and particle identification was performed by using the AE, , AE, and E signals. The solid angle and the angular acceptance of the spectrograph were 2.4 msr and O.&Y, respectively. The targets used were 58Ni (99.9% enriched, 0.473 mg/cm*), 60Ni (99.8% enriched, 0.493 mg/cm*) and 48Ca (97.7% enriched, 1.06 mg/cm*). The thickness of the 48Ca target was determined by comparing the measured elastic cross sections with the data at 65 MeV obtained by Sakaguchi er al. “). The overall energy resolution was about 20 keV FWHM. Two separated measurements for both s8Ni(p, p’)58Ni and 60Ni(p, p’)60Ni reactions with different magnetic field settings were carried out to cover the range of excitation energy from 2.0 MeV to 11.5 MeV in “Ni and from 7.5 MeV to 14 MeV in 60Ni respectively. Cross sections and analyzing powers were measured in the angular range of tflab= 8”-60” for 48Ca, eiab= lo”-48” for 58Ni and @rat, = lo”-40” for “Ni. The area and positions of the peaks in the spectra were determined by using a peak fitting program. The excitation energies were determined to an accuracy of +20 keV by calibrating the spectrograph with well determined energy values of the low-lying states in 58Ni and 60Ni. The uncertainty in the absolute values of the cross sections was estimated to be 10%. 3. Results Typical momentum spectra for 48Ca(p, p’)48Ca, 58Ni(p, p’)S8Ni and 60Ni(p, p’)60Ni inelastic scattering are shown in figs. 1-3. Although many states have been observed in the present experiment, we concentrate here on the l+ states. The angular distributions of cross sections and analyzing powers leading to the 10.22 MeV, 1’ state in 4*Ca are shown in fig. 4. These shapes of the angular distributions can be considered as the standard shapes of the angular distributions for the state with a (f;j2f,,,) wave function. The errors indicated in the figures include those caused from the peak fitting procedures in addition to the statistical ones. The angular distributions of cross sections and analyzing powers leading to the 10.66 MeV, 5.166 MeV and 2.903 MeV states in 58Ni which are known to be If states are shown in figs. 5, 6 and 7, respectively. The genera1 shapes of the angular distributions for the 10.66 MeV state in 58Ni which is known as a state with a (f;,‘:f,,,) isovector wave function, are similar to those of the 10.22 MeV state in 48Ca in fig. 5. While the shape of the angular distribution of the cross section leading to the 5.166 MeV state shows a forward peak and is similar to that of the 10.22 MeV state

240

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states

Fig. 1. Momentum spectrum of the inelastically scattered protons leading to the excitation energy region from 7 MeV to 11 MeV in ‘*Ca. LU(LD) means a spectrum taken with the spectrograph to the left side of the incident beam, which was polarized in the spin-up (spin-down) direction.

in ‘%a, the shape of the analyzing power is very different from that of the 10.22 MeV state as shown in fig. 6. The excitation of the 2.903 MeV state in 58Ni is dominated by AL = 2 transfer as described previously ‘*). The shape of the cross section is clearly different from those of the 10.66 and 5.166 MeV states. The angular distributions leading to the 11.86 MeV, l+ state in 60Ni are also shown in fig. 8. This state as well as the 10.66 MeV state in 58Ni are believed to be the states with the (f;,:f& isovector wave function. The general shapes of the angular dist~butions are also similar to the 10.22 MeV state in 48Ca and 10.66 MeV state in 5XNialready described. Angular shapes of the cross sections and the analyzing powers for more than 100 states in “Ni and 60Ni in the excitation region between 7 and 11 MeV were compared with those for the well known l+ states described above. From the comparison, we classified the states according to the similarities in the angular shapes of both cross sections and analyzing powers. The angular distributions are shown in figs. 5-8. The experimental shapes of both cross sections and analyzing powers leading to the 8.42 and the 9.28 MeV states in 58Ni and the 8.28 MeV state in 60Ni are very similar to those of the 10.66 MeV state in 58Ni and the 11.86 MeV state in “Ni as shown in figs. 5 and 8. From the similarity in the angular shapes, the 8.42 MeV and the 9.28 MeV states in 58Ni and the 8.28 MeV state in 60Ni can be identified as the candidates of the l+ states of a (f;jZf5,J configuration. The angular distributions for the 5.166 MeV, the 8.56 MeV and the 9.85 MeV states in ‘*Ni are similar to each other as shown in fig. 6. The angular distributions of cross sections for these states show a forward peak and the shapes of the analyzing powers are different from that of the 10.66 MeV state in “Ni with a (fYj2f5,J

K. Hosono

et al. / Ml states

NUMBER 5001

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241

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Fig. 2. Momentum spectra of the inelastically scattered protons leading to the excitation energy region from 2.5 MeV to 7.5 MeV and from 7.6 MeV to 11.5 MeV in ‘sNi. See also the caption for fig. 1.

configuration. The 5.166 MeV state has been assigned as the l+ state of a v(p,,,p,,,) configuration “). The 9.85 MeV state has been observed in inelastic electron 13,18) and proton “) scatterings and has been assigned as a l+ state although the configuration was not definite. The 8.56 MeV and the 9.85 MeV states in 58Ni can be identified as the candidates of the l+ states of a ~(p~,~p~,J configuration. The angular distributions of both cross sections and analyzing powers for the 2.903 MeV state in ‘*Ni and the 11.62 MeV state in 60Ni are very similar to each other and the cross section data shows a AL= 2 pattern as shown in fig. 7. The 2.903 MeV state was assigned as 1’ state with a v(p3,2fs,z) configuration I’). The 11.62 MeV state in 60Ni is a candidate of the l+ states of a v(pS12f5,J configuration.

242

+

~Ni(ff,P‘$%i EP=65 Me’/ t3=12* ifI

3 Fig. 3. Momentum spectra of the inelastically scattered protans leading to the excitation energy region from 7.3 h4eV to 11.9 MeV and from 10 MeV to 14 MeV in mNi, See alo the caption for fig. 1.

A state showing a forward-peak in the cross section was also observed at an excitation energy of 7.72 MeV in “Ni. The anguIar distributions are shown in fig. 9. The angular shape of the analyzing power, however, is different from those of the 5.156 MeV and the IO.66 MeV states in ‘*Ni. We did not observe at the measured angles the broad bump around 9 MeV which has been reported as an M 1 resonance “1.

4. Microscopic DWBA analysis and discussion In order to explain the characteristics of the ex~e~mental results, we carried out microscopic calculations of the angular distributions using the codes DWBA74

K. Hosono et al. / Ml states

4%Ca(p. pY%Ca Ep:65 MeV 10.218MeV. 1’

243

(b)

1, * l

L

-‘%

(

,

,

‘

20

km. 4o 6o Fig. 4. Angular distributions of cross section and analyzing power for the 10.22 MeV, I+ state in 48Ca. The curves are the microscopic DWBA calculations with M3Y effective interaction (a) and a density dependent effective interaction (b). C and T mean that the calcuiations were carried out with the central component alone and the tensor component alone, respectively. N is a normalization factor.

[ref. ‘“)I and DWBA83 [ref. ““)I which include both direct and exchange processes. The optical model parameter sets for the incident and outgoing protons were those derived by Sakaguchi et al. I’). For the states at an excitation energy of more than 10 MeV, the optical parameters in the exit channel were changed according to the systematics derived by Menet et al. **). Single particIe wave functions in the form factor were calculated in a Woods-Saxon well of radius R = 1.25 A*/3 fm, diffuseness a ==0.6fm, with a spin-orbit force of 6 MeV. In the calculations with the code

244

K. Hosono et al. / Ml states

Fig. 5. Angular dist~butions of cross sections and analyzing powers for the 10.66 MeV, 8.42 MeV and 9.28 MeV states in ‘*Ni. The curves are the microscopic DWBA predictions calculated with the M3Y interaction. The solid and dashed curves mean that the calculations were carried out with (f;/\fS12) isovector and isoscalar wave functions, respectively.

DWBA74, the M3Y potential 22) was used as the effective nucleon-nucleon interaction. The energy and density dependent effective interaction 23) at 100 MeV was used in the calculations with the code DWBA83. The anguiar distributions of the 10.22 MeV, l+ state in the 48Ca were observed as standard shapes for the state with its main component of a Y(f7/\f5& con~guration. In the calculations, a wave function derived by McGrory and Wildenthal 24) was used for the state. Though the fsi2 neutron is unbound, it is assumed to be tentatively baund by 0.02 MeV in the Woods-Saxon potential. The calculations with the code DWBA74 and the code DWBA83 are shown as solid curves in fig. 4. The solid curves show the calculations including all components of central, tensor and spinorbit forces and curves C and T show the calculations with the central force alone and the tensor force alone, respectively. N is the normalization factor which we multiplied the theoretical cross sections by before plotting. The calculations by the code DWBA83 are very similar to those by the code DWBA74 except for the normalization factor. The shape of the cross section data is well reproduced in both calculations. On the other hand, though the calculations can reproduce the general

K. Hosono et al. / MI states

245

Fig. 6. Angular distributions of cross sections and analyzing powers for the 5.166 MeV, 8.56 MeV and 9.85 MeV states in ‘*Ni. The solid curves are the microscopic DWBA predictions calculated with M3Y interaction and under the assumption of a pure v(p,,,p,,,) configuration.

feature of the analyzing power backward angles. The analyzing

data, they fail to describe the data very well at powers seem to be dominated by the exchange

amplitude arising from the tensor force at backward angles. The behavior of the analyzing powers may suggest that more complete wave functions are needed to describe them. Both cross sections and analyzing powers leading to the 10.66 MeV state in ‘*Ni and the 11.86 MeV state in 60Ni are very similar to those of the 10.22 MeV state in 48Ca. The 10.66 MeV and the 11.86 MeV states are known to be the states with (f7/\f5,J isovector wave functions. The states with similarity in the shapes of both cross section and analyzing powers are the 8.42 and the 9.28 MeV states in 58Ni and the 8.28 MeV state in 60Ni as shown in figs. 5 and 8. The 8.42 MeV state in “Ni may correspond to the 8.52 MeV state which was observed in electron inelastic scattering by Lindgren ef al. 13) They have reported that the 8.52 MeV state was excited by an M2 transition but that they could not eliminate a contribution from Ml transition. In the calculations for these states, we assumed a simple wave function with x&( 1rrf;,:f& f 1Vf7/:f5,J) configurations. The results of calculations using the M3Y effective interactions are shown in figs. 5 and 8, where the solid and the dashed curves indicate that the calculations were done using a pure isovector or isoscalar

246

K. Hosono et al. / MI states

Fig. 7. Angular dist~butions of cross sections and analyzing powers for the 2.903 MeV state in “Ni and the 11.62 MeV state in 6oNi. The solid curves are the microscopic DWBA predictions calculated with an M3Y interaction and under the assumption of a pure v(pjj2f5& configuration.

(f7$f5J wave function, respectively. The experimental shapes of the cross sections for the 10.66 MeV state in “Ni and the 11.86 MeV state in 60Ni are very well reproduced by the DWBA calcuIations with the isovector I+ wave function. Although the calculations can reproduce the gross shapes of the analyzing powers, they do not describe the data very well. This result is similar to the case of the 1+ state in 48Ca. The magnitudes of the no~alization factors are much smaller than that of 1” state in ‘?Za. In the calculations for the 8.42 MeV and the 9.28 MeV states in ‘*Ni and the 8.28 MeV state in 60Ni, the fits by DWBA calculations with isovector wave functions seem to be worse than those with isoscalar wave functions. The calculations show that these states in the Ml giant resonance region 6, may be candidates for the (f7>if5,J isoscalar li states and fragments of the Ml giant resonance. The angular distributions for the 5.166 MeV, the 8.56 MeV and the 9.85 MeV states in %i are similar to each other as shown in fig. 6. The 5.166 MeV state has been assigned as the l+ state of a ~(p~,~p~,~) configuration i2). In the DWBA calculation, a pure neutron wave function of the (p3,2p1,2) con~guration was assumed for the 5.166,8.56 and 985 MeV states. The wave function given in ref. “) was used

K. Hosono et al. /

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Ml states

I 0

I

I

40

20ec.m.

60

I

Fig. 8. Angular distributions of cross sections and analyzing powers for the 11.86 MeV and 8.28 MeV states in 60Ni. The curves are the microscopic DWBA predictions calculated with an M3Y interaction. The solid and dashed curves mean that the calculations were carried out with (f;/\fSIz) isovector and isoscalar wave function, respectively.

as the ground 0.3151vp$J.

state wave function in 58Ni, which was IO’) = 0.771 VP&)+ 0.5451 vf$,)+ The DWBA calculations with M3Y interaction are shown in fig. 6.

The calculations

can reproduce

well the shapes

of the angular

distributions

of the

cross sections and can describe the characteristic features of the analyzing power data. The strengths of the states at 9.85 MeV and 10.66 MeV are in the ratio of about 1: 1.3 in the (e, e’) experiment 13), whereas in the (p, p’) measurement by Djalali et al. 6), the value of this ratio is about 1: 5. We obtained the ratio of 1: 4.8 from the values in table 1. Djalali et al. “) suggest that the different relative strengths observed in the (e, e’) and (p, p’) experiments can be considered as an indication of a difference in the neutron-proton structure of these states and the 9.85 MeV state may have a higher multipolarity. From the results of the calculations, we suggest that the 5.166 MeV, the 8.56 MeV and the 9.85 MeV states are the l+ states which carry a large part of the (~~,~pr,J component. The 8.56 MeV and the 9.85 MeV states may be also fragments of Ml giant resonance as well as the 8.42 MeV and the 9.28 MeV states. In 60Ni, we could not observe the state with the (~~,~p,,~) configuration in the present experiment. The angular distribution of the cross section leading to the 7.72 MeV state in 58Ni, which has been reported and discussed 6,“*‘2.18), shows the shape for a AL=0

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7.72 i

Fig. 9. Angular distributions of cross section and analyzing power for the 7.72 MeV state in ‘*Ni. The curves are the microscopic DWBA predictions calculated with an M3Y interaction. The solid and dashed curves mean that the calculations were carried out with (f,$f,,,) isovector and isoscatar wave function, respectively. The dotted-dash curves are the results of ~lculat~ons under the a~umptio~ of a pure ~{p~,apt,~) configuration.

TABLE 1

Summary of the results of the well-known l+ states and the candidates of the 1’ states obtained from the present experiment and calculations

Excitation energy (MeV) ‘TZa: 10.22 “Ni: 8.42 9.28 10.66 5.166 8.56 9.85 2.903 60Ni: 8.28 11.86 11.62 “) Ref. I’).

Main configuration

Retative strength of integrated cross section (iO”-400)

DWBA74 “) (M3Y) ‘)

DWBA83 b, (Density dep.) d,

1.00 0.031 0.039 0.30 0.073 0.062 0.063 0.072 0.036 0.11 0.057

0.47 0.024 0.027 0.038 0.25 0.18 0.21 0.32 0.029 0.015 0.14

0.71 0.024 0.025 0.048 0.44 0.30 0.37 0.78 0.029 0.020 0.34

(f&f,,,) (f?;:fs,*) (f;;,f,,,) (f;:f,,*) (P3,*P,/2) (P3,2P*/2) (P3/2P1/2) (P3,2f5/2) (f$f,,*) (f$fs,*) fP3,&2) b, Ref. t9).

3 Ref. 2*).

d, Ref. 22).

N = ~(exp)/~(cai)

K. Hosono et al. / Ml states

249

transition as shown in fig. 9, but the shape of the angular distribution of the analyzing power is very different from that of the well-known l+ states in 58Ni. The DWBA calculations with the isoscalar and isovector (f7/\f& and the pure (~~,~p~,~)wave functions failed to reproduce the experimental data. This state is not the l+ state which carry a large part of the (f$f& or (pjjZpl,J component. The angular disstributions of both cross sections and analyzing powers for the 2.903 MeV state in 58Ni and the 11.62 MeV state in 60Ni are very similar to each other as shown in fig. 7. The 2.903 MeV state was assigned as It state with a v(p3,Jf5,2) configuration I*). The angular dist~butions for these states were compared with DWBA calculations. In the calculations for 58Ni, a pure neutron wave function with a v(p,,,f& configuration was assumed and the ground state wave function used was the one 25) described above. For the 11.62 MeV state in 60Ni, a pure v(p;&f& wave function was assumed. The calculations shown in fig. 7 can reproduce well the shape of the cross section data and can reproduce the feature the feature of the shapes of the analyzing power data. These states are suggested as one to be represented primarily by a i’(p;f2f512) configuration. In 58Ni, the Ml states at excitation energies of 10.18, 10.55 and 11.03 MeV have been observed in inelastic electron 13*”) and proton “) scattering experiments. At lower excitations three It states are reported at 6.05,6.41 and 7.09 MeV 13).However in the present measurement, these states are too weak to be unambigously identified.

Fig. 10. Relative strengths of the well known lc states and the candidates of the 1+ state suggested by the present experiment to the strength of the 10.22 MeV state in 48Ca. The strengths are derived from the integrated cross section from 10’ to 40”. Solid and dashed lines show the states with main configurations of (f$fs,z) and v(psi2p,,J, respectively. The dotted-dash lines show the states with mainly a V(p3,afs,a) configuration.

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Fig. 10 and table

1 show the relative

strengths

by the present

of the well known

experiment,

together

If states and

the possible

1’ states suggested

configuration calculations.

and the normalization factor between the experimental data and The relative strengths to that of the 10.22 MeV state in 48Ca are derived

with the main

from the integrated cross section from 10” to 40”. As shown in fig. 10, only a few narrow states that can be considered as candidates for l+ states were observed in the excitation energy of 7-11 MeV. Assuming the broad bump to be the isospin & part of the Ml resonance, Djalali et al. 6), calculated the ratio R= (da/dn)T,+,/(dcr/dn)~~ for 58Ni at 4”, including the high energy fine structure and the 10.18 MeV and 10.48 MeV states in the To+ 1 component and they obtained R = 0.77 -0.96. While, in our experiment, the relative strength of the integrated cross section for the 10.66 MeV, l+ (T = T,+ 1) state in 58Ni to the 10.22 MeV l+ in 48Ca is 0.30. Under the assumption that the bump consists of not only (f7/\f& isoscalar states but also the states with (p312p1,2) configuration, the sum of the strengths for the l+ states in the Ml resonance region which are the 8.42 MeV, 8.56 MeV, 9.28 MeV and 9.85 MeV states is 0.195. The ratio obtained is 1.54, which is larger than the value obtained by Djalali et al. The ratio is 3.1 for 60Ni. These results show that the weakly excited l+ states may be spread out beyond expectation and may be concealed by natural parity states at the measured angles larger than IO”. 5. Summary

We studied If states in 58Ni and 60Ni by using the 58Ni(p, p’)“Ni and 60Ni(p, p’)60Ni reactions at 65 MeV with high resolution. We concentrated in the analysis on the energy region of the bump interpreted as an Ml resonance “). The shapes of the angular distributions of both cross sections and analyzing powers for more than 100 states in 58Ni and 60Ni in the energy region of 7-11 MeV were compared with those for the well-known If states. From similarity in the shapes of the angular distributions and from comparison with microscopic DWBA calculations, four states in 58Ni and one state in 60Ni have been identified as the candidates for the If states. The candidates of the I+ states in the Ml resonance region are the 8.46 MeV and 9.28 MeV states in 58Ni and the 8.29 MeV state in 60Ni which carry a large part of the (f$f& component. The 8.56 MeV and 9.85 MeV states in “Ni are atso candidates of the 1+ states and can be represented primarily by a (~~,~p,,~) configuration. Though, we could not observe the states with a main configuration of (~~,~p,,~) in 60Ni, the bump observed at forward angles “) may consist of not only (f,\f,,,) isoscalar states but also the states with (p312p112) configuration. The observed Ml strength is very weak and many Ml excitations may be concealed by natural parity states at the present measured angles. This may imply that the Ml strength is strongly fragmented to a large number of very weak states. The authors would like to thank the staff members of RCNP, Osaka University for their generous support during the experiment. The experiment was performed

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at the RCNP under programs no. 17A19 and no. 18A23. The calculations were performed with the computers FACOM-18011 AD and FACOM-M200 at RCNP. References 1) C.D. Goodman, C.A. Goulding, M.B. Greenfield, J. Rapaport, D.E. Bainum, C.C. Foster, W.G. Love and F. Petrovich, Phys. Rev. Lett. 44 (1980) 1755 2) C. Gaarde, J. Rapaport, T.N. Taddeucci, C.D. Goodman, C.C. Foster, D.E. Bainum, C.A. Goulding, M.B. Greenfield, D.J. Horen and E. Sugarbacker, Nucl. Phys. A369 (1981) 258. 3) R. Pitthan and Th. Walcher, Phys. Lett. 36B (1971) 563. 4) R. Pitthan, 2. Phys. 260 (1973) 283. 5) R.M. Laszewski, R.J. Holt and H.E. Jackson, Phys. Rev. 13C (1976) 2257 6) C. Djalali, N. Marty, M. Morlet, A. Willis, J.C. Jourdain, N. Anantaraman, G.M. Crawley, A. Galonsky and P. Kitching, Nucl. Phys. A388 (1982) 1 7) F.E. Bertrand, E.E. Gross, D.J. Horen, J.R. Wu, J. Tinsley, D.K. McDaniels, L.W. Swenson and R. Liljestrand, Phys. Lett. 103B (1981) 326 8) D. Meuer, R. Frey, D.H.H. Hoffmann, A. Richter, E. Spamer and 0. Titze, Nucl. Phys. A349 (1980) 309 9) D. Meuer, G. Kiihner, S. Miiller, A. Richter, E. Spamer, 0. Titze and W. Kniipfer, Phys. Lett. 106B (1981) 289 10) K. Ackermann, K. Bangert, U.E.P. Berg, G. Junghans, R.K.M. Schneider, R. Stock and K. Wienhard, Nucl. Phys. A372 (1981) 1 11) G. P. A. Berg, W. Hiirlimann, I. Katayama, S. A. Martin, J. Meissberger, F. Osterfeld, J.G.M. Rijmer, B. Styczen, J. Tain, G. Gaul, R. Santo and G. Sondermann, in Proc. Conf. on spin excitations in nuclei, Telluride, Colorado, March 1982, p. 311 (Plenum, New York) 12) M. Fujiwara, Y. Fujita, I. Katayama, S. Morinobu, T. Yamazaki, H. Ikegami, S.I. Hayakawa and K. Katori, Nucl. Phys. A410 (1983) 137 13) R.A. Lindgren, W.L. Bendel, E.C. Jones Jr., L.W. Fagg, X.K. Maruyama, J.W. Lightbody Jr. and S.P. Fivozinski, Phys. Rev. 14C (1976) 1789 14) L.T. van der Bijl, H.P. Blok, J.F.A. van Hienen and J. Blok, Nucl. Phys. A393 (1983) 173 15) H. Ikegami, S. Morinobu, I. Katayama, M. Fujiwara and S. Yamabe, Nucl. Instr. Meth. 175 (1980) 335 16) Y. Fujita, K. Nagayama, S. Morinobu, M. Fujiwara, I. Katayama, T. Yamazaki and H. Ikegami, Nucl. Instr. Meth. 173 (1980) 265 17) H. Sakaguchi, M. Nakamura, K. Hatanaka, A. Goto, T. Noro, F. Ohtani, H. Sakamoto, H. Ogawa and S. Kobayashi, Phys. Rev. C26 (1982) 944 18) R. Frey, A. Friebel, H.D. Grlf, T. Grundey, G. Kiihner, W. Mettner, D. Meuer, A. Richter, G. Schrieder, A. Schwierczinski, E. Spamer, 0. Titze and W. Kniipfer, J. Phys. Sot. Japan Supp. 44 (1978) 202 19) R. Schaeffer and J. Raynal (unpublished) 20) H.V. von Geramb (unpublished) 21) J.J.H. Menet, E.E. Gross, J. Malanify and A. Zuker, Phys. Rev. C4 (1971) 1114 22) G. Bertsch, J. Borysowicz, H. McManus and W.G. Love, Nucl. Phys. A284 (1977) 399 23) H.V. von Geramb, L. Rikus and N. Nakano, Proc. 1983 Res. Cent. for Nucl. Phys. Intern. Symp. on light ion reaction mechanisms, Osaka, Japan, ed. H. Ogata, T. Kammuri and I. Katayama (RCNP, Osaka Univ., Osaka, Japan, 1983) p. 78 24) J.B. McGrory and B.H. Wildenthal, Phys. Lett. 103B (1981) 173 25) M.M. Stautberg, Phys. Rev. C3 (1971) 1541