Fragment spin correlations in damped nuclear reactions

Randrup, J.

doi:10.1016/0370-2693(82)90944-3

Cited by 10 publications

(2 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The bulk of the information on these fluctuations has been obtained from spin alignment studies, such as measurements of sequential fission fragment angular distributions [3][4][5][6] and the anisotropies of either continuum [-7, 8] or discrete [9,10] gamma-rays. While a variety of theoretical explanations for these fluctuations have been suggested, including vibrational modes [11,12], nucleon exchange [13][14][15][16], and the statistical excitation of collective modes [17,18], the underlying mechanism is still largely an open question. One important issue still to be resolved is the extent to which equilibrium is achieved for these fluctuations.…”

mentioning

confidence: 99%

Angular momentum alignment in the reaction154Sm+214 MeV32S

et al. 1984

View full text Add to dashboard Cite

Angular momentum alignment in the reaction 154Sm+214MeV 328 has been investigated using discrete-line 7-ray techniques. The anisotropies of stretched E2 transitions from the target-like fragments reach approximately three at the largest energy losses, implying rather strong alignment. The results are compared with the predictions of a simple model.Studies of the angular momentum transferred in heavy-ion collisions have proved very valuable in unraveling the complex dynamics of these reactions [1,2]. Although early efforts generally concentrated on the mean spin transfer, a variety of measurements have shown the importance of fluctuations about the mean value. The bulk of the information on these fluctuations has been obtained from spin alignment studies, such as measurements of sequential fission fragment angular distributions [3][4][5][6] and the anisotropies of either continuum [-7, 8] or discrete [9,10] gamma-rays. While a variety of theoretical explanations for these fluctuations have been suggested, including vibrational modes [11,12], nucleon exchange [13][14][15][16], and the statistical excitation of collective modes [17,18], the underlying mechanism is still largely an open question. One important issue still to be resolved is the extent to which equilibrium is achieved for these fluctuations. In order to obtain further insight into the origin of angular momentum fluctuations and their degree of equilibration, we have undertaken a detailed study of the reaction 154Sm+214MeV 328 utilizing the discrete-line method. This technique avoids problems connected with the unknown 7-ray multipolarities which arise in continuum studies and provides better exit channel definition than the sequential fission method. Exit channel selectivity may prove to * Present address: Department of Physics, University of Notre Dame, Notre Dame, IN 46556, USA be important in comparison with model calculations. A t.38mg/cm 2 thick, self-supporting foil of 1548m (99% enrichment) was bombarded with 214MeV 3287+ ions accelerated by the Texas A&M variableenergy cyclotron. Projectile-like fragments emitted at 0~a b = 47 ~ were detected and indentified in Z using a pair of solid state telescopes mounted in perpendicular planes (see the top of Fig. 1). Two high-resolution Ge(Li) detectors were placed in the horizontal plane at 90 ~ and 120 ~ with respect to the beam axis. During the measurements, particle-7, particle-v-7 events and scaled-down particle singles were recorded on tape in an event-by-event format. The beam intensity was controlled to minimize accidental coincidences (<8 %) and count rate instabilities in the Ge(Li) detectors (the average instantaneous rate was about 20kHz). The resolution (FWHM) integrated over eight days of running time was 3.5-4.0keV due to doppler broadening and some small gain shifts. In related experiments the continuum 7-ray multiplicities (Mr) were studied for the same reaction using an array of eight 7.6 x 7.6 cm NaI detectors. Experimental details regarding the M r measurements are reported elsewhere...

show abstract

mentioning

confidence: 99%

Angular momentum alignment in the reaction154Sm+214 MeV32S

et al. 1984

View full text Add to dashboard Cite

show abstract

“…Had this not been the case, the angular momenta generated by nucleon transfers would randomly sum and would result in mostly null value. The patterns of collective motion thus generated correspond to the wriggling mode of dinucleus rotations [8,[11][12][13], which is doubly degenerate, where the two fragments roll on each other with counter orbital rotation about their common center of mass to conserve total angular momentum.…”

Section: A Wriggling and Other Modes Of Dinuclear Rotationmentioning

confidence: 99%

Emergence of rotational modes in nuclear fission

John¹

2021

Preprint

View full text Add to dashboard Cite

Dinuclear systems that occur in the post-saddle to scission stage in nuclear fission process are special transient formations. The diabatic evolution at this stage has been studied using the methods of non-equilibrium thermodynamics. A novel explanation for spontaneous emergence of collective rotational modes in the dinucleus has been developed by identifying these modes together as an open subsystem that exchange matter and energy with its environment. The environment consists of all remaining degrees of freedom of the dinucleus, and a weak coupling of the subsystem to this environment facilitate a diabatic energy exchange. Under appropriate non-equilibrium conditions, the available energy will be coupled to the work needed for the emergence of self organizing rotational modes. This comes at the expense of increasing microscopic disorder in the form of intrinsic excitation in the fragments. A simple formalism is presented such that the magnitudes of relevant energy flow through the subsystem are obtained in terms of entropy production rate, entropy expulsion rate and net rate of change of entropy in unit of MeV zs -1 K -1 .

show abstract