NUCLEAR TRANSFER REACTIONS INDUCED BY 16O-IONS ON NUCLEI IN THE f-p SHELL

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NUCLEAR TRANSFER REACTIONS INDUCED BY 16O-IONS ON NUCLEI IN THE f-p SHELL

V. Manko, F. Becchetti, P. Christensen, R. Nickles

To cite this version:

V. Manko, F. Becchetti, P. Christensen, R. Nickles. NUCLEAR TRANSFER REACTIONS IN-

DUCED BY 16O-IONS ON NUCLEI IN THE f-p SHELL. Journal de Physique Colloques, 1971, 32

(C6), pp.C6-225-C6-227. �10.1051/jphyscol:1971650�. �jpa-00214868�

JOURNAL DE PHYSIQUE

Colloque C6, suppkment au no 11-12, Tome 32, Novembre-Dkcembre 1971, page C6-225

NUCLEAR TRANSFER REACTIONS INDUCED BY 160-IONS ON NUCLEI I N THE f-p SHELL

V. J. MANKO (*), F. D. BECCHETTI ("*), P. R. CHRISTENSEN and R. J. NICKLES (**") The Niels Bohr Institute, University of Copenhagen, Denmark

RBsum6. - Des rBactions du transfert de plusieurs nuclBons ont Bte BtudiBes avec un faisceau de

de 60 MeV sur les noyaux pair-pairs suivants : 40,48Ca, 50Ti, 52Cr, 54Fe,

8760362364Ni et 64Zn. On observe une grande variation des sections efficaces de ces rbactions avec la cinkmatique.

Abstract.

Multi-nucleon transfer reactions have been studied with a 60 MeV

beam on the even-even target nuclei : 40,48Ca, 50Ti, 52Cr, 54Fe,

8,60,62,64Ni and 64Zn. A strong kine- matic dependence of the cross sections of these reactions is deduced.

The 60 MeV 160-beam from the FN-tandem accelerator of the Niels Bohr Institute was used for studies of nuclear transfer reactions on the even-even target nuclei 40,48Ca, 50Ti, 52Cr, 54Fe, 5 8 9 6 0 3 6 2 9 6 4 ~ i and 64Zn. Reaction products were detected with a AE-E telescope consisting of 20 micron and 100 micron silicon counters. The different carbon and nitrogen isotopes could be separated with this system. The overall energy resolution was usually about 300 keV.

Details of the experimental set-up and procedures will be published elsewhere.

The following reactions have been observed in the present experiment :

1) one-proton transfer (160, 15N) reaction on all of the targets studied ;

2) two-proton transfer (160, 14C) reaction on 50Ti, 52Cr, 54Fe and Ni-isotopes ;

3) deuteron transfer (160, 14N) reaction on 54Fe ; 4) (160, 13N) reaction on 54Fe ;

5) (160, 13C) reaction on 58Ni ;

6) (160, I2C) reaction on all the target nuclei.

The reactions 1)-5) were found t o be strongly selective in the excitation of levels in the residual nuclei.

In the single-proton transfer reaction (160, 15N) single-particle levels known from (3He, d) reaction are populated. One can also identify states which appear to be single-particle states coupled to collective states

(*)

On leave from the

V. Kurchatov Institute, Moscow, U. S. S. R.

(**)

N. S. F. Fellow.

(*

*

James A. Picker Fellow.

of the target nucleus. Similar states in the Zr-region were discussed in another work [I]. In the two-proton transfer reaction (160, 14C) collective states are strongly excited. There is no enhancement in the population of Of states as in the case of two-nucleon transfer reactions with light ions [2], [3]. In figure 1 the energy spectrum of the outgoing particles from 64~i(160,

)

Z reaction is shown. The most strongly excited state is the collective 3- state at 2.8 MeV. Very similar are the spectra of the (160, 14C) reaction on the other Ni-isotopes, as one can see in figure 2.

E x , MeV

FIG.

-The energy spectrum of the 64Ni(160,

reaction at

MeV,

The selectivity of the nuclear transfer reactions with heavy ions together with the measured angular distributions suggest that they have a direct mecha- nism and can become useful in nuclear spectroscopy.

However, in order to get quantitative data on

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1971650

C6-226

MANKO, F. D. BECCHETTI, P. R. CHRISTENSEN AND R. J. NICKLES nuclear structure, it is necessary to account for all

kinematic effects. In the present experiment it was found that kinematic effects play an important role in heavy ion reactions by investigations of transitions between

6 L N i ( 1 6 0 , 1 L C ) 6 6 Z n

Qo= -5.98 MeV

62Ni'('60,1LC)

Zn Q O = -8.50 MeV

3-

'jONi (1 6 0 , 1 L C ) 6 2 Z n GIo= -11.10L MeV

saNi (160.1LC) 60Zn

= -13.8 MeV

Ex, MeV

2. -The energy spectra of the

58,60,62,64Ni(160,14C)60,62964,66Zn.

All transitions are normalized to the groundstate transition for each isotope.

Ni (160 '5N

60

9%

\

-

FIG.

Q-dependence of the cross sections of the (160, 15N) reaction on the nickel isotopes divided

CZS(2J +

similar states using the (160, I5N) and the (l6OY 14C) reactions on the Ni-isotopes. Since the proton configurations, of all the isotopes are very similar, differences in the cross sections of the one- or two- proton transfer reactions, populating similar states in either Cu or Zn isotopes should be mainly due to kine- matic effects. In figure 3 the cross sections of the tran- sitions to the single-particle 2p3,, (g. s.) and lg,,, states in the 58,60,62,64~i(160

Y

divided by C2S(2 j + 1) found from (3He, d) reac- tion [4] are plotted versus the Q-values. In figure 4 the cross section for the transitions to the Oi and 3- states in the 58,60,62,64~qi(l60,

reactions are shown. One can notice the strong 1

Q-dependence of the cross sections. The cross sections change by more than one order of magnitude from 6 4 ~ i to 58Ni.

Ni (160,1LC) Zn 60

35"

0.001

0 5 10 15

-Q

FIG. 4.

Q-dependence of the cross sections of the

14C) reaction on the nickel isotopes.

The strong Q-dependence of the cross sections is

most likely connected with the mismatch of the classical

orbits in the initial and final channels [5]. In figures 5

and 6 the same quantities as in figures 3 and 4 are

plotted versus differences of the closest approach

distances in the initial and final channels AD. We

have calculated AD using Rutherford-orbits and taking

into account the angular momentum transfer. It is

NUCLEAR TRANSFER REACTIONS INDUCED BY "0-IONS C6-227 seen that in all the cases the cross sections are decrea-

sing very rapidly with increasing mismatch of the two orbits. Similar cross section dependences have been observed in the Z r region [1J.

A D f m A D , f m

FIG. 5. — A£>-dependence of the cross sections of the (

0,

N) reaction on the nickel isotopes, divided by C

S(2J + 1).

FIG. 6. — AD-dependence of the cross sections of the (

«0, '

C) reaction on the nickel isotopes.

References [1] NlCKLES (R. J.), MANKO (V. J.). CHRISTENSEN (P. R.)

and BECCHETTI (F. D.), Phys. Rev. Letters, 1971, 26, 1267.

[2] BOHR (A.), Proceedings of the international symposium on nucl. str. (Dubna, 1968), 179.

[3] NATHAN (O.), Proceedings of the international sym- posium on nucl. str. (Dubna 1968), 191.

[4] PULLEN (D. J.) and ROSNER (B.), Phys. Rev., 1968, 170,

1034;

BLAER (A. J.), Phys. Rev., 1965, 140, B648.

[5] BUTTLE (P. J. A.) and GOLDFARB (L. J. B.), to be

published.