Three-body Breakup Research Articles

Mechanism of Coulomb breakup reactions of two-neutron halo nuclei 6He and 11Li

We investigate the three-body Coulomb breakup reactions of two-neutron halo nuclei and discuss the correlations of every binary subsystem such as of core-n and n-n by showing the invariant mass spectra. It is found that the final-state interactions of core-n and n-n binary subsystems dominantly determine the observed energy distributions of the breakup cross sections, such as the low-lying enhancements. Furthermore, we investigate the effects of the 9Li core excitations on the Coulomb breakup cross section of 11Li. It is shown that the integrated E1 strength at low energy region is reduced by ~ 15 % by the inclusion of the 9Li core excitations.

CDCC studies on clustering physics

The continuum-discretized coupled-channels method (CDCC) has successfully been applied to studies on various reactions involving unstable nuclei. The four-body CDCC method is a new method to calculate three-body breakup continuum in a projectile, which gives an accurate analysis for four-body breakup systems. The eikonal reaction theory is a new approach to calculate inclusive breakup cross sections such as neutron removal cross sections. Moreover, CDCC is a useful tool for evaluation of nuclear data, which are important for nuclear engineering.

Continuum ppΛ spectrum of the He3(K−,π−) reaction with continuum discretized coupled channels

Abstract We theoretically investigate an inclusive π − spectrum of a He 3 ( K − , π − ) reaction at 870 MeV/c in a distorted-wave impulse approximation using the continuum discretized coupled channels (CDCC) method, in order to well describe the pp continuum states above the p + p + Λ breakup threshold. We calculate the continuum ppΛ states applying the multichannel Green's function with a microscopic 2 N – Λ folding-model potential constructed by the CDCC wavefunctions. The results show that the calculated spectra reproduce available experimental data, and that the pp continuum states lying in higher energies are needed to fully describe these spectra, depending on the momentum transfer in the ( K − , π − ) reaction. It is shown that this calculation provides the ability of describing three-body ppΛ breakup systems for the ( K − , π − ) spectra.

Break-up channels in muon capture onHe3

The mu + 2H -> nu + n + n, mu + 3He -> nu + 3H, mu + 3He -> nu + n + d and mu + 3He -> nu + n + n + p capture reactions are studied with various realistic potentials under full inclusion of final state interactions. Our results for the two- and three-body break-up of 3He are calculated with a variety of nucleon-nucleon potentials, among which is the AV18 potential, augmented by the Urbana~IX three-nucleon potential. Most of our results are based on the single nucleon weak current operator. As a first step, we have tested our calculation in the case of the mu + 2H -> nu + n + n and mu + 3He -> nu + 3H reactions, for which theoretical predictions obtained in a comparable framework are available. Additionally, we have been able to obtain for the first time a realistic estimate for the total rates of the muon capture reactions on 3He in the break-up channels: 544 1/s and 154 1/s for the n + d and n + n + p channels, respectively. Our results have also been compared with the most recent experimental data, finding a rough agreement for the total capture rates, but failing to reproduce the differential capture rates.

The H + HeH(+) → He + H2(+) reaction from the ultra-cold regime to the three-body breakup: exact quantum mechanical integral cross sections and rate constants.

In this work, we present a quantum mechanical scattering study of the title reaction from 1 mK to 2000 K. Total integral cross sections and thermal rate constants are compared with previous theoretical and experimental data and with simpler theoretical models to understand the range of validity of the approximations used in the previous studies. The obtained quantum reactive observables have been found to be nearly insensitive to the roto-vibrational energy of the reactants at high temperatures. More sensitive to the reactant's roto-vibrational energy are the data in the cold and ultra-cold regimes. The implications of the new data presented here in the early universe scenario are also discussed and analyzed.

Study of Borromean halo nuclei by the neutron wall with simulation

The model of three-body Borromean halo nuclei breakup was described by using standard phase space distributions and the Monte Carlo simulation method was established to resolve the detection problem of two neutrons produced from breakup reaction on the neutron wall detector. For 6He case, overall resolution σEk for the Gaussian part of the detector response and the detection efficiency including solid angle acceptance with regard to the excitation energy Ek are obtained by the simulation of two neutrons from 6He breakup into the neutron wall. The effects of the algorithm on the angular and energy correlations of the fragments are briefly discussed.

Simultaneous probing of geometry and electronic orbital of ArCO by Coulomb-explosion imaging and angle-dependent tunneling rates

We simultaneously probe the molecular structure and the symmetry of valence electronic orbital of an anisotropic atomic-molecular complex of ArCO by tracing its three-body Coulomb breakup following triple ionization in a phase-controlled elliptically polarized two-color pulse. The geometry of ArCO is found to be tilted T shaped, where the angle between the covalent and van der Waals bonds is 65\ifmmode^\circ\else\textdegree\fi{} with oxygen pointing towards argon. The asymmetric profiles of the outmost orbitals from the CO site are probed by directional dissociation of the contained CO subunit as a function of the laser phase. Our results clearly image the asymmetric geometry of ArCO and thus reveal the anisotropic interaction between a rare-gas atom and a heteronuclear diatomic molecule.

Spin observables in the three-body break-up process near the quasi-free limit in deuteron–deuteron scattering

We have studied spin observables in the three-body break-up reaction in deuteron–deuteron scattering in the phase-space regime that corresponds to the quasi-free deuteron–proton scattering process with the neutron as spectator. The data are compared to measurements of the elastic deuteron–proton scattering process and state-of-the-art Faddeev calculations. The results for iT11 and T22 for the quasi-free scattering data agree very well with previously published elastic-scattering data. A significant discrepancy is found for T20, which could point to a break-down of the quasi-free assumption.

Mechanisms of Coulomb breakup reactions of 6He and 11Li

We investigate the three-body Coulomb breakup reactions of two-neutron halo nuclei and discuss the effect of binary subsystem correlations such as the of core-n and n-n. Furthermore, we calculate the invariant mass spectra. It is found that the final-state interactions of core-n and n-n binary subsystems dominantly determine the observed structures of the breakup cross sections, such as the low-lying enhancements.

Coulomb breakup reactions of11Li in the coupled-channel9Li+n+nmodel

We investigate the three-body Coulomb breakup of a two-neutron halo nucleus ${}^{11}$Li. We use the coupled-channel ${}^{9}$Li+$n$+$n$ three-body model, which includes the coupling between last neutron states and the various two-particle--two-hole ($2\text{p}$-$2\text{h}$) configurations in ${}^{9}$Li due to the tensor and pairing correlations. The three-body scattering states of ${}^{11}$Li are described by using the combined methods of complex scaling and the Lippmann-Schwinger equation. The calculated breakup cross section successfully reproduces the experiments. The large mixing of the $s$ state in the halo ground state of ${}^{11}$Li is shown to play an important role in the explanation of shape and strength of the breakup cross section. In addition, we predict the invariant mass spectra for binary subsystems of ${}^{11}$Li. It is found that the two kinds of virtual $s$ states of ${}^{9}$Li-$n$ and $n$-$n$ systems in the final three-body states of ${}^{11}$Li largely contribute to make low-lying peaks in the invariant mass spectra. On the other hand, in the present analysis, it is suggested that the contributions of the $p$-wave resonances of ${}^{10}$Li are hardly confirmed in the spectra.

Hyperspherical Coulomb spheroidal basis in the Coulomb three-body problem

A hyperspherical Coulomb spheroidal (HSCS) representation is proposed for the Coulomb three-body problem. This is a new expansion in the set of well-known Coulomb spheroidal functions. The orthogonality of Coulomb spheroidal functions on a constant-hyperradius surface ρ = const rather than on a constant-internuclear-distance surface R = const, as in the traditional Born-Oppenheimer approach, is a distinguishing feature of the proposed approach. Owing to this, the HSCS representation proves to be consistent with the asymptotic conditions for the scattering problem at energies below the threshold for three-body breakup: only a finite number of radial functions do not vanish in the limit of ρ→∞, with the result that the formulation of the scattering problem becomes substantially simpler. In the proposed approach, the HSCS basis functions are considerably simpler than those in the well-known adiabatic hyperspherical representation, which is also consistent with the asymptotic conditions. Specifically, the HSCS basis functions are completely factorized. Therefore, there arise no problems associated with avoided crossings of adiabatic hyperspherical terms.

Coulomb Breakup Reactions of Two-Neutron Halo Nuclei 6He and 11Li Using Complex-Scaled Solutions of the Lippmann–Schwinger Equation

We investigate the three-body Coulomb breakup reactions of two-neutron halo nuclei and discuss the effect of binary subsystem correlations such as of core–n and n–n. We furthermore calculate the invariant mass spectra. It is found that the final-state interactions of core–n and n–n binary subsystems dominantly determine the observed structures of the breakup cross sections, such as the low-lying enhancements.

Time-Dependent Electron Interactions in Double Rydberg Wave Packets

We investigate the time-dependent evolution of a nonstationary three-body Coulomb system at energies just below the threshold for three-body breakup. Experimentally, short-pulse lasers excite two electrons in Ba to radially localized Rydberg wave packets with well-defined energy and angular momentum. Time-dependent interactions between the two electrons are probed using half-cycle electric field pulses. The measurements indicate that substantial energy exchange between the two electrons is nearly immediate upon the launch of the second wave packet. Fully quantum and classical calculations support this observation, predicting extremely rapid autoionization under the experimental conditions. The calculations also show very fast angular momentum exchange and sensitivity to the relative binding energies of the two electrons.

Universal three-body recombination via resonantd-wave interactions

For a system of three identical bosons interacting via short-range forces, when two of the atoms are about to form a two-body s-wave dimer, there exists an infinite number of three-body bound states. This effect is the well-known Efimov effect. These three-body states (Efimov states) are found to be universal for ultracold atomic gases and the lowest Efimov state crosses the three-body break-up threshold when the s-wave two-body scattering length is $a \approx -9.73 r_{\rm vdW}$, $r_{\rm vdW}$ being the van der Waals length. This article focuses on a generalized version of this Efimov scenario, where two of the atoms are about to form a two-body d-wave dimer, which leads to strong d-wave interactions. In a recent paper [B. Gao, Phys. Rev. A. {\bf 62}, 050702(R) (2000)], Bo Gao has predicted that for broad resonances the d-wave dimer is always formed near $a \approx 0.956 r_{\rm vdW}$. Here we find that a single universal three-body state associated with the d-wave dimer is also formed near the three-body break-up threshold at $a \approx 1.09 r_{\rm vdW}$ and its signature can be found through enhancement of the three-body recombination. The three-body effective potential curves that are crucial for understanding the recombination dynamics are also calculated and analyzed. An improved method to calculate the couplings, effective potential curves, and recombination rate coefficients is presented.

Use of generalized hyperspherical Sturmian functions for a three-body break-up model problem

A hyperspherical Sturmian approach recently developed for three-body break-up processes is tested through an analytically solvable S-wave model. The scattering process is represented by a non-homogeneous Schrödinger equation in which the driven term is given by a Coulomb-like interaction multiplied by the product of a continuum wavefunction and a bound state in the particles' coordinates. The model contains most of the difficulties encountered in a real three-body scattering problem, e.g., non-separability in the electrons' spherical coordinates and Coulombic asymptotic behaviour, and thus provides an interesting benchmark for numerical methods. Since the Sturmian basis functions are constructed so as to include the correct asymptotic behaviour, a very fast convergence of the scattering wavefunction is observed. Excellent agreement is found with the analytical results for the associated transition amplitude. This holds true down to very low energies, a domain which is usually challenging as it involves huge spatial extensions. Within our method, such calculations can be performed without increasing significantly the computational requirements.

On the numerical treatment of Coulomb forces in scattering problems

We investigate the limiting procedures to obtain Coulomb interactions from short-range potentials. The application of standard techniques used for the two-body case (exponential and sharp cutoff) to the three-body break-up problem is illustrated numerically by considering the Temkin-Poet (TP) model of e-H processes.

Modern approaches for the theoretical description of multiparticle scattering and nuclear reactions

A review of novel approaches to solution of multiparticle scattering problems in the area above three-body breakup together with the review of new computational technologies which provide very effective and ultrafast realization of the novel approaches with ordinary PC are given. The novel direction presented here is based on two key points: a new formulation of the quantum scattering theory in a discrete Hilbert space of stationary wave packets and the massive-parallel solution of the resulted matrix equations with usage of ultrafast graphic processors (the so called GPU-computations). For the reader’s convenience, a short review of the modern GPU calculations for the medicine, physics, military applications etc. is presented.

An analytically solvable three-body break-up model problem in hyperspherical coordinates

An analytically solvable S-wave model for three particles break-up processes is presented. The scattering process is represented by a non-homogeneous Coulombic Schrodinger equation where the driven term is given by a Coulomb-like interaction multiplied by the product of a continuum wave function and a bound state in the particles coordinates. The closed form solution is derived in hyperspherical coordinates leading to an analytic expression for the associated scattering transition amplitude. The proposed scattering model contains most of the difficulties encountered in real three-body scattering problem, e.g., non-separability in the electrons’ spherical coordinates and Coulombic asymptotic behavior. Since the coordinates’ coupling is completely different, the model provides an alternative test to that given by the Temkin-Poet model. The knowledge of the analytic solution provides an interesting benchmark to test numerical methods dealing with the double continuum, in particular in the asymptotic regions. An hyperspherical Sturmian approach recently developed for three-body collisional problems is used to reproduce to high accuracy the analytical results. In addition to this, we generalized the model generating an approximate wave function possessing the correct radial asymptotic behavior corresponding to an S-wave three-body Coulomb problem. The model allows us to explore the typical structure of the solution of a three-body driven equation, to identify three regions (the driven, the Coulombic and the asymptotic), and to analyze how far one has to go to extract the transition amplitude.

Frustrated tunnelling ionization during strong-field fragmentation of D3+

We reveal surprisingly high kinetic energy release in the intense-field fragmentation of D3+ to D+ + D+ + D with 1016 W cm−2, 790 nm, 40 fs (and 7 fs) laser pulses. This feature strongly mimics the behaviour of the D+ + D+ + D+ channel. From the experimental evidence, we conclude that the origin of the feature is due to frustrated tunnelling ionization, the first observation of this mechanism in a polyatomic system. Furthermore, we unravel evidence of frustrated tunnelling ionization in dissociation, both two-body breakup to D + D2+ and D+ + D2, and three-body breakup to D+ + D + D.

Three-body breakup within the fully discretized Faddeev equations

A novel approach is developed to find the three-body breakup amplitudes and cross sections within the modified Faddeev equation framework. The method is based on the lattice-like discretization of the three-body continuum with a three-body stationary wave-packet basis in momentum space. The approach makes it possible to simplify drastically all the three- and few-body breakup calculations due to discrete wave-packet representations for the few-body continuum and simultaneous lattice representation for all the scattering operators entering the integral equation kernels. As a result, the few-body breakup can be treated as a particular case of multi-channel scattering in which part of the channels represents the true few-body continuum states. As an illustration for the novel approach, an accurate calculations for the three-body breakup process $n+d\to n+n+p$ with non-local and local $NN$ interactions are calculated. The results obtained reproduce nicely the benchmark calculation results using the traditional Faddeev scheme which requires much more tedious and time-consuming calculations.