LXXI International conference "NUCLEUS – 2021. Nuclear physics and elementary particle physics. Nuclear physics technologies"

THE ALIGNMENT OF THE ${}^{16}O$($3^-$; 6.131 MeV) NUCLEUS FORMED IN SOME NUCLEAR REACTIONS AT $E_x\approx 7.5$ MeV/NUCLEON

21 Sept 2021, 18:00

2h

Poster report Section 1. Experimental and theoretical studies of the properties of atomic nuclei. Poster session (Experimental and theoretical studies of the properties of atomic nuclei)

Speaker

Nataliia Zelenskaya (M.V. Lomonosov Moscow State University)

Description

Experimental and calculated the $F_2(\theta_y)$ and $F_4(\theta_y)$ alignment angular dependences of the ${}^{16}O$ nucleus in the excited state $3^-$ (6.131 MeV), formed in the reactions ${}^{16}O(\alpha,\alpha)^{16}O$, ${}^{14}N(\alpha, d)^{16}O$, ${}^{15}N(\alpha, t)^{16}O$ and ${}^{19}F(p,\alpha)^{16}O$ at energies $E_\alpha = 30.3$ MeV and $E_p = 7.5$ MeV are presented. The orientation parameters $F_k$ ($k =1,\dots,2J, |F_k| \le 1$) are polynomials in the mean values of the powers $\langle J_z\rangle$ and are included in the expression for the interaction energy of nuclei with an electromagnetic field [1]. The parameter of the dipole orientation $F_1$ is called polarization, and the quadrupole $F_2$ is the alignment of the nuclei. Since the method of angular correlations used in this work makes it possible to experimentally determine only even components, we consider the parameters of the quadrupole $F_2$ and hexadecapole $F_4$ orientations. In the case of an isotropic spin distribution, the alignment is zero. The maximum value of the parameters is achieved at the maximum value of the spin projection $M=J$ onto the quantization axis:

$F_2=\frac{2J+1}{\sqrt{5}}\sqrt{\frac{(J+1)(2J+3)}{J(2J-1)}} T_{20},$ $F_4=\frac{2J+1}{6}\sqrt{\frac{(2J+3)(2J+2)(2J+4)(2J+5)}{J(J-1)(2J-1)(2J-3)}} T_{40} ,$ $T_{k0}=\frac{1}{2J+1}\frac{\rho_{k0}(\theta_y)}{\rho_{00}(\theta_y)},$

where $\rho_{k0}(\theta_y)$ is the spin tensor component of the nucleus density matrix.
Experimental information was obtained on the basis of previously retrieved [2-5] spin-tensors $\rho_{kK}(\theta_y)$ density matrices of the ${}^{16}O$ nucleus ($3^-$; 6.131 MeV) by measuring of the angular particle-gamma correlations.
The experimental orientation parameters are compared with the calculated ones under the assumption of the mechanisms of stripping or pickup a nucleon cluster by the coupled channel method (FRESCO code [6]) and a compound nucleus (TALYS code [7]). The features of the behavior of the orientation parameters of the ${}^{16}O$ nucleus ($3^-$; 6.131 MeV) formed in various reactions are discussed and compared.

1. G.R. Khutsishvili. Uspekhi Fizicheskikh Nauk. V.53, P. 381 (1954).
2. A.V. Ignatenko et al. Izvestiya RAN. Seriya Fizicheskaya. V.58, P. 188 (1994).
3. A.V. Ignatenko et al. Yadernaya Fizika. V. 61, P. 5 (1998).
4. A.V. Ignatenko et al. Izvestiya RAN. Seriya Fizicheskaya. V. 66, P. 1507 (2002).
5. A.V. Ignatenko et al. Izvestiya RAN. Seriya Fizicheskaya. V. 60, P. 189 (1996).
6. I. J. Thompson. Comp. Phys. Rep. 7, 167 (1988); http://www.fresko.org.uk/.
7. A.J. Koning, S. Hilaire, and M. C. Duijvestijn. TALYS: AIP Conf. Proc. 769, 1154 (2005); https://tendl. web.psi.ch/tendl_2019/talys.html.