Ishizaki, Yoshihide

Kokame, June

Nonaka, Itaru

Ogata, Hiroshi

Saji, Yoshio

Stricker, Andere

Suehiro, Teruo

Sugiyama, Yasuharu

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Title The ¹⁵⁸Gd(p, t)¹⁵⁶Gd Reaction (Memorial IssueDedicated to the Late Professor Yoshiaki Uemura)Author(s)Ishizaki, Yoshihide; Kokame, June; Suehiro, Teruo; Saji,Yoshio; Ogata, Hiroshi; Nonaka, Itaru; Stricker, Andere;Sugiyama, YasuharuCitationBulletin of the Institute for Chemical Research, KyotoUniversity (1974), 52(1): 165-169Issue Date1974-07-25URL http://hdl.handle.net/2433/76530RightType Departmental Bulletin PaperTextversionpublisherKyoto UniversityBull. Inst. Chem. Res., Kyoto  Univ., Vol. 52; No. 1               The 158Gd(p, t)156Gd Reaction      Yoshihide ISHIZAKI, June KOKAME*, Teruo SUEHIRO**, Yoshio SAJI***,        Hiroshi OGATA****, Itaru NONAKA*****, Andere STRICKER****** and Yasuharu SuGIYAMA*******                                Received December 12,1973     The 1s6Gd(p, t)156Gd reaction has been measured at 51.9 MeV of incident energy. The  excited states of 1.83 MeV 2+, 2.01 MeV (0++2+), 2.22 MeV 2+, 2.37 MeV 2+, 2.60 MeV (4+), and  3.29 MeV (6+) have been newly observed. The possibility of the new rotational band of k=0 is dis- cussed. One of the quadrupole pairing vibrational states is pointed out.                           I. INTRODUCTION    The (p, t) and the (t, p) reactions on the even-even nuclei in the rare earth region were measured by some groups.1-15)     In the measurements1-4,6^'9, 11,12) on the nuclei in the transitional region, the rotational band structures of k=0 were observed at the excited states of the nearly spherical nuclei in the ground states and also the existence of the nearly spherical states at the excited states of deformed nuclei in the ground states became clear.    In the 176Yb(p, t)174Yb reaction some excited rotational bands of k=0, each moment of innertia of which was almost the same as that of the ground band, were observed.5)    In the (p, t) reactions on Nd isotopes, the pairing vibrational 0+ states16,17) and the quadrupole pairing vibrational 2+ states were measured' 3' 15) and theoretically analyzed.' 8)    We have measured again the (p, t) reactions systematically in the rare earth region at the incident energy of 51.9 MeV to study the higher excited states than those reported in Ref. 10. This high incident energy is useful for the measurement of the high spin states and highly excited states. Here we report the higher excited states of 15 6Gd than already measured states by (p, t) reaction.10 12)              II. EXPERIMENTAL PROCEDUREAND RESULTS    51.9 MeV proton beam for this experiment was provided by the Institute for        * Ea4iff*y, /Jv , : Institute for Nuclear Study, University of Tokyo, Tanashi, Tokyo.       ** *11-,1 : Tohoku Institute of Technology, Koshiji, Nagamachi, Sendai. * * * (f : Faculty of Engineering, Miyazaki University, Nishi-Maruyama, Miyazaki-Shi.     **** /J\ : Research Center for Nuclear Physics, Osaka University, Yamada, Suita, Osaka.    ***** 43gJ : Faculty of Science, Chiba University, Yayoi, Chiba.   ****** A. Stricker: Tokyo Keiki Landaisgyr Co. Ltd. Ginza Ono Build., 1-17 Tsukiji, Tokyo. * * * * * * * ' 11j j : Nuclear Physics Laboratory, Japan Atomic Energy Research Institute, Tokai-         Mura, Ibaragi. (165)                                                        Y.  ISHIZAKI et al.           Nuclear Study synchrocyclotron, and the emitted tritons were analyzed with the magnetic           analysis system and detected by a proportional-counter array.' 9) The target of isoto-          pically enriched oxide Gd203 (97.58%) was deposited on a mylar backing by a centrifu-          gal setting method and the thickness was 1.82 mg/cm2. The overall energy resolution           was about 90 keV FWHM.              Figure 1 shows a triton momentum spectrum. Above the excitation energy of          about 1.9 MeV this spectrum has a background due to the high level density in this.           region. This kind of background is also seen in the spectra measured with a high resol-          ution6' 8) and is reasonably considered by the energy gap. This background prevents           reliable cross section measurements for the peaks in higher excitation energy than           2 MeV. The differential cross sections for the peaks were extracted by subtracting           this background which is given in Fig. 1 by a broken line and is smoothly continuous           to the spectrum measured till about 10 MeV excitation energy. Subtracted background           had almost the same shape of the angular distribution as that corresponding to the higher           excitation energy region where no peaks were observed. yea o C" Cnannal15eGd (p, t) 156Gd                                         2500 Ep=51.9MeV eL= 5.0                20002.z`2M4/2•                                      2.3 )                       15002.60)J•1                             13 351ceLlt.13 MeV 2I•t.15MeV 2-   A,                                                                                                                                                                                                                                                          • 1000_ ,                              .•1i.01 MaV 10..2.)89NeV\24                               •t .63 MeV 2105MeV a      500*I/                                                                                                                         5952.0'                                                                                                           1.32MeV9                                                                                                         a97MeV32666-,a                           Fig. 1. A typical momentum spectrumoftritons.A broken line gives the                                background ue to the high level density.              The differential cross sections for the peaks at 1.83, 2.01, 2.22, 2.37, 2.60, and 3.29 MeV excitation energies are shown in Fig. 2 together with those for the members of the           ground state band to compare the shapes. In Ref. 10, angular distributions for the           ground band 4+ states were very different in the deformed region.            The solid lines in Fig. 2 are the DWBA predictions. All the theoretical fits are           arbitrarily normalized.              The DWBA analysis for the ground state band members measured by us1o) were           already performed by two groups.2°-23) In both cases the best fit parameters of the optical potential are almost the same. In Ref. 20 the value of N4 affected not           only the magnitude but also the shape of the differential cross section for the ground           band 4+ state, but in Ref. 23 the value of )64 affected only the magnitude. In Fig. 2           DWBA curve for the 4+ state is given with Y4=0 in Ref. 20, and all the DWBA curves (166) 158Gd(p, t) 156Gd Reaction 158Gd(p, f)156Gd Ep=51.9MeV 50-50-                                                  f              N           440-1'~5885 keV 6+10_\fi•—f\ 3.29 McV(6+)          v5-9:IiT954\ i~•-'jR                      i\v\k\a\    i,o\I        io-isf ioo-12.60                                                  MeV         ~4—pf:~.\;ix(4+)                5- i si288 keV4+                 50- \ 1                  \..\4f\Ii I 2.37 McV(2+) 100100—5••I~ 50~+50-fl1                       89 keV 2         .f.• f 2.22 MeV 2+             NI......,\4\f I If     II     100: I~    •i        50- 57If 2.01MeV •' gnd 0+/s'II(0++2*)        10-rt\ 10-Isf         5-I 5-\T1.83MeV 2+ . 11I . 1 1 1 t ,- .. I0 20 30 40 50 10 20 30 40 50 e C.H.(deg)eC.H (deg)               Fig. 2. Experimental and theoretical angular distributions obtained from the 156Gd (p, t) 156Gd reaction at E5=51.9 MeV. The solid curves are                     the DWBA predictions calculated in Ref. 20-23.   given for the newly observed states are the same as those for the ground state band    members. c III. DISCUSSION       From the DWBA calculations we have deduced that the newly observed peaks at ,   1.83, 2.01, 2.22, 2.37, 2.60, and 3.29 MeV correspond to the states of 2+, (0++2+), 2+, 2+, (4+), and (6+) respectively. Because of the weak resolution of our measurement   it is less accurate that each of these peaks in Fig. 1 corresponds to only one state,   compared to high resolution measurement. But the measurement with high resolution   and high incident energy is not yet performed.      It is very interesting that the level spacing of the (0+) component of 2.01 MeV (167)                                                    Y. ISHIZAKI et al.           state, 2.22 MeV  2+ state, 2.60 MeV (4+) state and 3.29 MeV (6+) state is very like           to be that of the rotational band of k =0. In all the excited bands of k =0 measured           by (p, t) reactions at the incident energies of nearly 20 McV,3-8) 0+ state member has           the larger sum of the differential cross sections at measured angles(summed cross section)           than any one of the other members. In the measurement at 51.7 MeV reported in Ref.          10 and in this experiment at 51.9 MeV the 1.13 MeV $ vibrational 2+ state and 1.15           MeV y vibrational 2+ state of 156Gd are not resolved, and the sum of the cross sections           for these two 2+ states is much larger than the cross section for the (3 vibrational 0+           state. The above mentioned situation is the same for 2.01 MeV 0+ and 2.22 MeV 2+ states, and 2.22 MeV 2+ state has the larger cross section than that for 2.01 MeV 0+ state.               However, if the states of 2.01, 2.22, 2.60, and 3.29 MeV construct the rotational           band, special mechanism of excitation by the (p, t) reaction should be considered.              The 2.37 MeV 2+ state has also the large cross section. We consider this state to          be one of the quadrupole pairing vibrational states which will be connected to those           observed in Nd isotopes.13' 14,1 s) Our systematic measurements of the states which           look to be the quadrupole pairing vibrational states in 148Sm, 1soSm, 152Sm, 156Gd,           162Dy, and 170Yb will be reported elsewhere.24)                                    ACKNOWLEDGMENTS              Authors wish to offer this report to the late Professor Yoshiaki Uemura of the           Keage Laboratory of Nuclear Science, Institute for Chemical Research, Kyoto Univer-         sity. They are indebted to Mr. I. Sugai of the Isotope Separation Division of the          Institute for Nuclear Study, University of Tokyo, led by Professor K. Kaneko, for the          preparation of the target, and also to Miss K. Hiraide of the same institute for the          drawing of the figures and typewriting of the manuscript.              One of the authors (Y.I.) wishes to thank Professor M. Sano and his group T.          Takemasa and H. Toki of the Faculty of Science, Osaka University for their valuable            discussion.                                     REFERENCES (1) S. Hinds, J. Bjerregaard, O. Hansen, and O. Nathan, Phys. Lett., 14, 48 (1965). (2) J. Bjerregaard, O. Hansen, O. Nathan, and S. Hinds, Nucl. Phys., 86, 145 (1966). (3) J. R. Maxwell, G. M. Reynolds, and N. M. Hintz, Phys. Rev., 151, 1000 (1966). (•4) P. Debenham and N. M. Hintz, Phys. Rev. Lett., 25, 44 (1970). (5) M. Oothoudt, N. M. Hintz, and P. Vedelsby, Phys. Lett., 32B, 270 (1970). (6) P. Debenham and N. M. Hintz, Nucl. 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The ¹⁵⁸Gd(p, t)¹⁵⁶Gd Reaction (Memorial Issue Dedicated to the Late Professor Yoshiaki Uemura)

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The ¹⁵⁸Gd(p, t)¹⁵⁶Gd Reaction (Memorial Issue Dedicated to the Late Professor Yoshiaki Uemura)

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