Highly excited “nuclear molecules”: A way to explain the fluctuations in DBHIC excitation functions. Study of the28Si +28Si colliding system at 5.3 MeV ·A

Abstract

Abstract. The properties of the strong fluctuations observed in the excitation functions of Dissipative Binary Heavy Ion Collisions (DBHIC) have been studied for the system 2Ssi+ 28 Si in the energy range 150MeV < El~b _< 156MeV with 150keV step laboratory incident energy, by angular distributions and excitation functions measurements. Experimental results are compared to the the recently developed Partially Overlapping Molecular Level Model (POMLM). The parameters of the model have been determined with reasonable accuracy by describing all the quantities characterizing the fluctuations in the excitation functions i.e.: Average Angular Distributions, Energy Autocorrelation Functions, Variances, Angular Correlation Coefficients. The results of the analysis strongly support the idea of a process proceeding through the formation of an highly excited "nuclear molecule". Experimental data collected at the most forward angles show the effects of strong excitation of a few final channels.

Fourier analysis of nonself-averaging quasiperiodic oscillations in the excitation functions of dissipative heavy-ion collisions: quantum chaos in dissipative heavy-ion collisions?

“…This effect was first discovered and reported in [34] and further measurements [32,33,[35][36][37][38][39][40][41][42][43][44][45] have confirmed the universality of this phenomenon.…”

“…system), on which we consider the problem, satisfies the inequality 2I ≤ d~ω, where ω is the angular velocity of coherent rotation [5]. Typical estimates of~ω for systems studied up until the present [32][33][34][35][36][37][38][39][40][41][42][43][44][45] …”

“…We suggest that such measurements do not introduce into the intermediate system a perturbation which could destroy the above mentioned quantum effects. If this suggestion is correct, then the study of excitation function oscillations in DHIC [32][33][34][35][36][37][38][39][40][41][42][43][44][45] relates to the point of view [6]: "No matter how negligible the probability, in view of the thousands of experiments already done, any new possibility like quantum chaos should be used carefully to check the fundamental equations in the laboratory again and again". This paper is a compact account of the main steps and results obtained by the stochastic modelling of excitation function oscillations in DHIC within the model of statistical reactions with memory [5].…”

Statistical reactions with memory and thermalized-nonequilibrated nuclear states

“…However, it is relevant to also comment briefly on the possible manifestation of this phenomenon in heavy-ion collisions. In particular, memory effects are suggested [24] to be a sufficient condition to explain nonselfaveraging of the excitation function oscillations in dissipative heavy-ion collisions [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46]. It has also been found that spin and parity S-matrix correlation allows one to account for the oscillating non-Lorentzian behaviour of the cross section energy autocorrelation functions in 58 Ni + 62 Ni elastic and inelastic scattering [47].…”

S-matrix spin and parity decoherence and damping of coherent nuclear rotation: quantum chaos in dissipative heavy-ion collisions?

“…[Indeed, such a division is justified provided the spreading width Γ coll,rot spr of the collective rotational states (if excited at all in DHIC before the neutron and γ-ray cascad emission) is much less than the inverse average life-time of the intermediate nucleus. The latter is of order of the characteristic energy scale δε 100-500 keV [7][8][9][10][11][12][13][14][15][81][82][83][84] of the excitation function fine structures in DHIC. DHIC are characterized by high excitations (20 MeV or more) above the Yrast line.…”