Few-body semiclassical approach to nucleon transfer and emission reactions

A three-body semiclassical model is proposed to describe the nucleon transfer and emission reactions in a heavy-ion collision. In this model the two heavy particles, i.e. nuclear cores A$_1(Z_{A_1}, M_{A_1})$ and A$_2(Z_{A_2}, M_{A_2})$, move along classical trajectories $\vec R_1(t)$ and $\vec R_2(t)$ respectively, while the dynamics of the lighter neutron, n, is considered from a quantum mechanical point of view. Here, $M_i$ are the nucleon masses and $Z_i$ are the Coulomb charges of the heavy nuclei ($i=1,2$). A Faddeev-type semiclassical formulation using realistic paired nuclear-nuclear potentials is applied so that all three channels (elastic, rearrangement and break-up) are described in an unified manner. In order to solve these time-dependent equations the Faddeev components of the total three-body wave-function are expanded in terms of the input and output channel target eigenfunctions. In the special case when the nuclear cores are identical (A$_1 \equiv$ A$_2$) and the two-level approximation in the expansion over target functions the time-dependent semiclassical Faddeev equations are resolved in an explicit way. To determine the realistic $\vec R_1(t)$ and $\vec R_2(t)$ trajectories of the nuclear cores a self-consistent approach based on the Feynman path integral theory is applied.Comment: 15 pages, 1 figur

Low-energy muon-transfer reaction from hydrogen isotopes to helium isotopes

Direct muon transfer in low-energy collisions of the muonic hydrogen H$_\mu$ and helium (He$^{++}$) is considered in a three-body quantum-mechanical framework of coordinate-space integro-differential Faddeev-Hahn-type equations within two- and six-state close coupling approximations. The final-state Coulomb interaction is treated without any approximation employing appropriate Coulomb waves in the final state. The present results agree reasonably well with previous semiclassical calculations.Comment: 4 revtex4 page

State-resolved rotational cross sections and thermal rate coefficients for ortho-/para-H2+HD at low temperatures and HD+HD elastic scattering

Results for quantum mechanical calculations of the integral cross sections and corresponding thermal rate coefficients for para-/ortho-H2+HD collisions are presented. Because of significant astrophysical interest in regard to the cooling of primodial gas the low temperature limit of para-/ortho-H2+HD is investigated. Sharp resonances in the rotational state-resolved cross sections have been calculated at low energies. These resonances are important and significantly contribute to the corresponding rotational state-resolved thermal rate coefficients, particularly at low temperatures, that is less than $T \sim 100$K. Additionally in this work, the cross sections for the elastic HD+HD collision have also been calculated. We obtained quite satisfactory agreement with the results of other theoretical works and experiments.Comment: 16 pages, 5 figures, additional results include

Ultracold collisions between two light indistinguishable diatomic molecules: elastic and rotational energy transfer in HD+HD

A close coupling quantum-mechanical calculation is performed for rotational energy transfer in a HD+HD collision at very low energy, down to the ultracold temperatures: $T \sim 10^{-8}$ K. A global six-dimensional H$_2$-H$_2$ potential energy surface is adopted from a previous work [Boothroyd {\it et al.}, J. Chem. Phys., {\bf 116}, 666 (2002).] State-resolved integral cross sections $\sigma_{ij\rightarrow i'j'}(\varepsilon_{kin})$ of different quantum-mechanical rotational transitions $ij\rightarrow i'j'$ in the HD molecules and corresponding state-resolved thermal rate coefficients $k_{ij\rightarrow i'j'}(T)$ have been computed. Additionally, for comparison, H$_2$+H$_2$ calculations for a few selected rotational transitions have also been performed. The hydrogen and deuterated hydrogen molecules are treated as rigid rotors in this work. A pronounced isotope effect is identified in the cross sections of these collisions at low and ultracold temperatures.Comment: 9 pages, 9 figures. Accepted for publication in Physical Review

Determination of the temperature of a dense plasma from a spectral line shift

The method of maximum spectral line shift proposed by Bardocz, et al, (1966) was successfully applied in the diagnostics of dense plasmas produced by high power pulse discharges. It is pointed out that the effect of the shock wave pressure on the spectral line shift has to be taken into account in order to obtain accurate results with this method for high power discharges. A pressure dependent function was introduced in the expression given by those authors to provide the necessary correction