Coulomb excitation in intermediate-energy collisions

“…The inclusion of relativistic effects in semiclassical and quantum formulations of Coulomb excitation was discussed in Refs. [48,47]. Recently, the importance of relativistic effects in Coulomb excitation of a projectile by a target with charge Z 2 , followed by gamma-decay, in nuclear reactions at intermediate energies was studied in details.…”

Section: Pos(enas 6)023mentioning

confidence: 99%

Theory of the Coulomb Dissociation

Bertulani¹

2013

Proceedings of VI European Summer School on Experimental Nuclear Astrophysics — PoS(ENAS 6)

View full text Add to dashboard Cite

We observe photons and neutrinos from stars. Based on these observations, complemented by measurements of cosmic rays energies and composition, we have been able to constrain several models for the Big Bang and for stellar evolution. But that is not enough. We also need to help this effort with laboratory experiments. We are still far from being able to reproduce stellar environments in a terrestrial laboratory. But in many cases we can obtain accurate nuclear reaction rates needed for modeling primordial nucleosynthesis and hydrostatic burning in stars. The relevant reactions are difficult to measure directly in the laboratory at the small astrophysical energies. In recent years indirect reaction methods have been developed and applied to extract low-energy astrophysical S-factors. These methods require a combination of new experimental techniques and theoretical efforts, which are the subject of this short review.

show abstract

“…This was achieved by solving the general classical problem of the motion of two relativistic charged particles [17]. The role of the nuclear excitations was also investigated by performing full quantum mechanical calculation of the Coulomb, nuclear as well as of their interference terms, using a collective model prescription for the nuclear form factor.…”

Section: Riken Data E Beam ∼ 50 Mev/nucleonmentioning

confidence: 99%

“…(1) n πλ (E γ ) represents the number of equivalent (virtual) photons provided by the Coulomb field of the target to the projectile, which is calculated by the method discussed in Ref. [7,17] . S(E cm ), can be directly determined from the measured Coulomb dissociation cross-sections using Eqs.…”

Section: Riken Data E Beam ∼ 50 Mev/nucleonmentioning

confidence: 99%

Breakup of 8B and the 7Be(p, γ)8B reaction

Shyam

Thompson

1999

Pramana - J Phys

View full text Add to dashboard Cite

Abstract. The calculated rate of events in some of the existing solar neutrino detectors is directly proportional to the rate of the 7 Be(p, γ) 8 B reaction measured in the laboratory at low energies. However, the low-energy cross sections of this reaction are quite uncertain as various measurements differ from each other by 30-40 %. The Coulomb dissociation process which reverses the radiative capture by the dissociation of 8 B in the Coulomb field of a target, provides an alternate way of accessing this reaction. While this method has several advantages (like large breakup cross sections and flexibility in the kinematics), the difficulties arise from the possible interference by the nuclear interactions, uncertainties in the contributions of the various multipoles and the higher order effects, which should be considered carefully. We review the progress made so far in the experimental measurements and theoretical analysis of the breakup of 8 B and discuss the current status of the low-energy cross sections (or the astrophysical S-factor) of the 7 Be(p, γ) 8 B reaction extracted therefrom. The future directions of the experimental and theoretical investigations are also suggested. IntroductionThe 8 B isotope produced in the Sun via the radiative capture reaction 7 Be(p,γ) 8 B is the principal source of the high energy neutrinos detected in the Super-Kamiokande (SK) and 37 Cl detectors [1]. In fact the calculated rate of events in SK as well as SNO detectors [3] is directly proportional to the rate of this reaction measured in the laboratory at low energies (∼ 20 keV) [3]. Unfortunately, the measured cross sections (at relative energies (E CM ) of [p −7 Be] > 200 keV) disagree in absolute magnitude and the value extracted by extrapolating the data in the region of 20 keV differ from each other by 30-40 %. This makes the rate of the reaction 7 Be(p, γ) 8 B the most poorly known quantity in the entire nucleosynthesis chain leading to the formation of 8 B [4]. It may be noted that the rate of the 7 Be(p,γ) 8 B reaction is usually given in terms of the zero-energy astrophysical S-factor, S 17 (0).The Coulomb dissociation (CD) method provides an alternative indirect way to determine the cross sections for the radiative capture reactions at low energies [5,6,7,8,9]. In this procedure it is assumed that the break-up reaction a+Z → (b+x)+Z proceeds entirely via the electromagnetic interaction; the two nuclei a and Z do not interact strongly. By further assuming that the electromagnetic excitation process [5, 6]) the measured cross-sections of this reaction to those of the radiative capture reaction b + x → a + γ. Thus, the astrophysical S-factors of the radiative capture processes can be determined from the study of break-up reactions under these conditions. However, in the CD of 8 B, the contributions of E2 and M 1 multipolarities can be disproportionately enhanced in certain kinematical regimes [10,11]. Furthermore, interference from the nuclear breakup processes may also be considerable in some regions. Therefore, a ...

show abstract

Coulomb excitation in intermediate-energy collisions

Cited by 55 publications

References 5 publications

Direct Reactions for Nuclear Astrophysics

Direct Reactions for Nuclear Astrophysics

Theory of the Coulomb Dissociation

Breakup of 8B and the 7Be(p, γ)8B reaction

Contact Info

Product

Resources

About