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Orbiting: Toward a unified model of nucleus‐nucleus collision or excitation of nuclear molecular states in heavy ion collisions?

 

作者: A. Ray,   D. Shapira,  

 

期刊: AIP Conference Proceedings  (AIP Available online 1992)
卷期: Volume 250, issue 1  

页码: 55-74

 

ISSN:0094-243X

 

年代: 1992

 

DOI:10.1063/1.42008

 

出版商: AIP

 

数据来源: AIP

 

摘要:

It has been suggested that damped reaction reaction products at backward angles from the28Si+12C,24Mg+12C and20Ne+12C reactions result from the formation of long‐lived orbiting complexes. This suggestion was originally made on the basis of the observation that the total integrated binary yields are much larger than the predictions of compound nucleus calculations although they follow a 1/sin &thgr;c.m.angular distribution near 180°. Subsequent studies have confirmed the noncompound origin of these yields through the observations of entrance channel dependence of back‐angle yields and strong selectivity of natural parity states. However, it has also been found that the formation of an orbiting complex and the associated back‐angle ‘‘anomalies’’ are not universal. It appears that the formation of orbiting complex dominates the back‐angle yields for systems having a small number of open channels. This is similar to the systematic behavior that was observed for the anomalous back‐angle elastic scattering and suggests that the same physical process might be responsible for back‐angle elastic scattering and suggests that the same physical process might be responsible for back‐angle anomalies in elastic and inelastic channels. Recently new insight has been obtained about orbiting reaction mechanism from the measurement of the complete gamma‐ray angular correlations for the28Si+12C orbiting system.It has been found that the measured density matrices for the12C(2+) and28Si states are almost diagonal with respect to the direction of motion of the fragments. The measured density matrices and spin alignments are consistent with the picture of formation of a long‐lived dinuclear complex undergoing orbiting, bending and wriggling motions, but not with those obtained from statistical compound nucleus or sticking model calculations.

 

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