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Submitted on 1 Jan 1971
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ELASTIC SCATTERING OF Li6 ON C12 AND O16
V. Chuev, V. Davidov, B. Novatskii, A. Ogloblin, S. Sakuta, D. Stepanov
To cite this version:
V. Chuev, V. Davidov, B. Novatskii, A. Ogloblin, S. Sakuta, et al.. ELASTIC SCATTERING OF Li6 ON C12 AND O16. Journal de Physique Colloques, 1971, 32 (C6), pp.C6-161-C6-162.
�10.1051/jphyscol:1971627�. �jpa-00214845�
JOURNAL DE PHYSIQUE Colloque C6, supplkment a u no 1 1-12, Tome 32, Novembre-Dkcembre 1971, page C6-161
ELASTIC SCATTERING OF Li6 ON C t 2 AND
016V. I. CHUEV, V. V. DAVIDOV, B. G. NOVATSKII, A. A . OGLOBLIN, S. B. SAKUTA and D. N. STEPANOV
Kurchatov Institute of Atomic Energy, Moscou, USSR
Rbumh. - La diffusion elastique des ions Lis sur Cl: et 0 1 6 a ete mesuree a une energie inci- dente de 30 MeV. Les sections efficaces ont une structure prononcke aux grands angles et remon- tent fortcment a I'arriere. Les resultats sont compares a des calculs dans le cadre du modele optique.
Abstract. -The elastic scattering of Li6 ions on C12 and 0 1 6 was measured at an incident energy of 30 MeV. The cross sections have pronounced structure at large angles and strong back- ward peaking. The results are compared with thc optical-model calculations.
The elastic scattering of Li6 ions on C I 2 and 0 1 6 has been studied a t ELi = 30 MeV within c. m. angles from 150 to 1750. The carbon and L i 2 0 self-suppor- ting foils were used as targets. The angular distribu- tions obtained have a rather complicated diffraction picture (Fig. 1). Pronounced oscillations a t the large scattering angles and strong backward peaking are observed. Deep and wide minima a t the angle of about 1000 exist as if dividing the differential cross section curves into two parts.
The angular distributions were analyzed in terms of the optical model. The nuclear potential was repre- sented a s the volume absorption potential without the spin-orbital term :
The best fit to the experimental data (Fig. Ib) was obtained with approximately the same set of para- meters as for heavier nuclei [I]. An important feature of this set is a deep real potential well, V ,
-
250 MeV.No parameter set with the V, values from 20 to 150 MeV could describe the rise in the angular dis- tributions of
c''
and 0 1 6 for the backward hemisphere.The potential parameters chosen by a minimum of X 2 are listed in the table I.
E V W YO", r o w , a" aw, Cr
Nucleus MeV MeV MeV f f f f mbarn
The Coulomb potential was taken in the form of a uniform charged sphere of the radius R, = 1.4 A ' / ~ . First an attempt was made to explain the data using a four-parameter potential with the same geometry for real and imaginary parts (r,, = row, a, = a,).
The optimum values of the potential were obtained : for C12 V = 21.8 MeV, W = 13.2 MeV, a = 0.66 f and for 0'" = 25.2 MeV, W = 13.0 MeV, a = 0.69 f.
The interaction radius in both cases was taken in the form of R = (1.2 A ' / ~
+
2.2 f). The curves calcu- lated with the above parameters gave reasonable fits to the data in the range of angles from 20° to 800 and strong discrepancy for angles larger than 900 (Fig. la).The calculations with independent real and imagi- nary potential geometries were performed a t different starting values of the potential for C1' and 016.
The fits are surprisingly good. Indeed, for large angle region they are better than in the case of heavier nuclei [I]. This means, however, that the result obtaincd must be taken with caution.
An alternative explanation of the backward struc- ture of the angular distributions can be proposcd on the basis of the multinucleon transfer mechanism.
In the case under consideration the Li6-cluster exchange should occur. Though possible (the ((effective num- ber )) of Li6-cluster in the p-shell nuclei is about 0.1 [2]) this process seems very improbable due to the high binding energy of Li6 in C'' and 016. A similar situation takes place in the case of He3 or triton scattering on Li6 (the ct effective number )) of He3-clusters or tritons in Li6 is large, of order of unity, and the binding energies are high). The expe- riment on ~e~
+
Li6 scattering [3], however, shows no structure or peaking a t large anglcs contrary to the Li6+
C12 or ~i~+
0 1 6 scattering.Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1971627
V. 1. CHUEV, V. V. DAVIDOV, B. G . NOVATSKI1
FIG. 1. - Diffcrential cross sections of 1-i" - Cl2 and Lib
+
0 1 6 elastic scattering.a) Comparison with four-parameter optical-model calculations (the parameters are given in the text).
b) Comparison with six-parameter optical-model calculations (parameters are given in Table I).
References
El] CHUEV (V. I.), DAVIDOV (V. V.), NOVA~SKII (B. G.), ciatioxls in light nuclei. (( N a u k a )). Moscow, OGLOBIN (A. A.), SAKUTA (S. R.), STEPANOV (D. 1969.
N.), This Conference. [3] C H U E V (V. I.), DAVIDOV (V. V.), NOVATSKII (B. G.), OGLOBLIN (A. A.), SAKUTA (S. B.), STEPANOV 121 NEVDATCHM (V. G.), SMIRNOV (Yu.), Nucleon asso- (D. N.), This Conference.
