HAL Id: jpa-00214834
https://hal.archives-ouvertes.fr/jpa-00214834
Submitted on 1 Jan 1971
HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
DETERMINATION OF THE CHARACTERISTICS OF UNSTABLE STATES EXCITED IN THE C12(Li6,
d)O16 REACTION BY α - d ANGULAR CORRELATION MEASUREMENTS
K. Artemov, V. Goldberg, I. Petrov, V. Rudakov, I. Serikov, V. Timofeev
To cite this version:
K. Artemov, V. Goldberg, I. Petrov, V. Rudakov, I. Serikov, et al.. DETERMINATION OF THE CHARACTERISTICS OF UNSTABLE STATES EXCITED IN THE C12(Li6, d)O16 REACTION BYα- d ANGULAR CORRELATION MEASUREMENTS. Journal de Physique Colloques, 1971, 32 (C6), pp.C6-125-C6-126. �10.1051/jphyscol:1971616�. �jpa-00214834�
JOURNAL DE PHYSIQUE Colloque C6, supplkment au no 1 1-12, Tome 32, Novembre-Decemhre 1971, page C6-125
DETERMINATION OF THE CHARACTER1 STIC S OF UNSTABLE STATES EXCITED IN THE C1 2(Li6, d)Ot6 REACTION BY a - d ANGULAR CORRELATION MEASUREMENTS
K. P. ARTEMOV, V. Z. GOLDBERG, I. P. PETROV, V. P. RUDAKOV, I. N. SERIKOV and V. A. TIMOFEEV
Kurchatov Institute of Atomic Energy, Moscou-U. S. S. R.
RhumC. - La correlation angulaire d-a de la reaction ClZ(Li< d)016(6+, 16,2 MeV) (a, C::) a ete CtudiCe. Elle est proportionnelle au polyn6me de Legendre d'ordre 6.
Abstract. - The d-a coincidence angular correlation in the CIZ(Li6, d)016(6+, 16.2 MeV)
(a, C:?) reaction has been studied. It was found to be proportional to the Legendre polynomial of order 6.
in recent years, there has been considerable inte- rest in the structure of states excited in the (Li6, d) and (Li7, t) reactions [I]-[3]. Knowledge is necessary, however, of the main characteristics of states : spins, parities, partial and total widths, in order to under- stand their nature. Unfortunately, the angular distri- butions are rather shapeless in the region of high excitation and in the transition of a large orbital moment, and the determination of state spins by the shape of the angular distributions becomes ambi- guous.
A method is known for the determination of the above characteristics of the nuclear state unstable relative to the production of heavy particles by the measurement of angular correlations in the decay of this state 141, 151. If in the CL2(Li6, d)Ot6(a, cir2) the angular correlation between the deuterons out- going a t 00 with respect to the beam and decay par- ticles, the function of the angular correlation has the form W(0) = Bm I Y,,,,(O) l 2 143 , where the proba-
m
bility of population, B,,, of different reactions of the first state spin I, m, = 0, + 1, t_ 2, ...(I m, I < I )
depends on the reaction mechanism and can be found from the comparison of W(0) with the cor- relation function measured. The probabilities Bm for nz # 0 should be suppressed if the (Li6, d) reaction proceeds by the simple mechanism invol- ving the transfer of an cr-particle. Moreover, the same result should be expected a t a small (but not equal tb zero) angle of deuteron detection. We made attempts to determine the kind of the correlation function in the C12(Li6, d)016(6+, 16.2 MeV) (cw, c::) reaction. The measurements were performed using a 26 and 30.7 MeV Li6 beam from the Kurchatov Atomic Energy Institute cyclotron. Three measure-
ment runs were carried out. In the first run deuterons were detected at ELi = 26.0 MeV a t angle of Od = 00, in the second and third runs - a t ELi = 30.7 MeV and a t 100.
After passing through the filter where the Li beam was slowed down the deuterons arrived a t the telescope dE/dX-EV(telescope 1, Q = 2 x The second teles- cope (telescope 2, !2 = 2.5 x recorded the x-decay particles. T o select desired events, the signals from the two telescopes are fed to the electron system containing four 4096-channel analyzers which provide the information exchange with the high-speed computer in the course of the experiment. The system gave the two-dimensional display in the energy coordinates of Ed-E, in the scale of 256-256 (channels) corres- ponding to deuteron and a-particle coincidence (z,,,,,. < 40 s) selected by two particle identificators.
A detailed description of the system can be found in Ref. [6]. On the Ed-E plane the events corresponding to the formation of the d, a-particle and c:? in the final state weve seen as a narrow intense band. Less intense bands corresponding to the formation of the a-particle and C12 in the excited states of 2+(4.43 MeV) and 3-(9.66 MeV) were seen as well.
The band reflecting the formation of CI2 in the state of OP(7.66 MeV) was not observed practically.
Figure 1 shows the measured correlations for the decay to the a-particle and 0;: from the state of 16.2 MeV (6') for the three above measurement runs.
The correlation function measured a t the angle of deuteron detection equal to O0 is normalized in the
2 1 + 1
absolute value to the function of 4 7c [p,(cos t))]
which is necessary because of the difficulty in measu- ring deuterons at OO. No normalization was made
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1971616
C6-126 K . P. ARTEMOV, V. 2. GOLDBERG ET I. P. PETROV
for the measurements at 100 in the lab. system except for a small shift of the experimental points along the horizontal axis, 3 O and 60, for energies of bombar- ding particles 30.7 and 26 MeV, respectively. This shift is associated rather with the distorsion of the incident wave Li6 in the input channel of the reaction.
A good fitting of calculated and measured curves indicates the dominant probability of the population of the rn = 0 projection of the spin of the state under investigation in the C12(Li6, d ) 0 I 6 ( 6 + , 16.2 MeV) reaction by a reliable method for the determination of state characteristics (I).
Thus, it should be expected that the measured
"I functions of angular correlation between the deuteron
FIG. 1. - Angular correlation in thc CIz(Li6, d)016(a)~:: for from the c I 2 ( ~ i 6 , d ) 0 ' 6 reaction recorded a t a small the 16.2 MeV state of 0 1 6 . The solid curve represents the corre- angle and a-dccay particles of the state 016 Will be lation function of (1314 K) [ ~ ~ ( c o s 8)]2. The white points corres-
pond to the Li6 energy of 30.7 MeV (Blab = lo0 for the deuteron described by a simple expression and can serve as counter). black to the energy of 26 M ~ V (olab = 10") a reliable method for the determination of the charac-
crosses-to the energy of26 MeV (&at, - On). teristics of nuclei states.
References
I l l GOLDBERG (V. 2.) et al., Izv. Acad. Naulc SSSR, [4] KUCHKER (J. A.), Phys. Rev., 1962, 125, 1651.
Ser. Fiz.. 1969, 33, 566. [5] GOBRI (A.) et al., Plzys. Rev. Letters, 1971, 26, 396.
f2] MEIER-EWEKT (K.), BETGE (K.) and PFEIFFER (K.-O.), [6] ARTEMOV (K. P.), GOLDBERG (V. Z.), PETROV (Y. P.), Nucl. Phys., 1968, A 110, 142. RUDAKOV (V. P.) and SERIKOV (Y. N.), SOV.
131 COMFORT (I. R.) et al., Phys. Letters, 1970, 32B, 685. Jourtz. o f Nucl. Phys., 1970, 12, 1108.
