Huili Han

Hyperspherical coupled channel calculations for the spectra and structure parameters of rare gas trimers NeAr2 and Ne2Ar

We calculate the L=0 vibration energies and rotational constants for the van der Waals trimers 20NeAr2, 20Ne2Ar, and their corresponding isotopologues within the framework of hyperspherical coordinates. The Schrodinger equation in hyperangular coordinates is solved at a series of fixed hyper-radii using B-splines and the resulting coupled hyper-radial equation is solved using the slow variable discretization method developed by Tolstikhin et al. [J. Phys. B 29, L389 (1996)]. Using the special properties of B-splines, we make the knot distributions more precisely, characterizing the behavior of channel functions. Our method improves the convergence greatly. It turns out that our numerical tool works quite well in study of rare gas trimers. Calculations are performed on two kinds of pair potentials, the HFD-B and Tang-Toennies (TT) potentials, and the resultant rotational constants and their isotope shifts are compared with the experimental results obtained from high-resolution spectroscopy. The TT pair potentials give much better agreement with the experimental values for 20Ne2Ar and 22Ne2Ar trimers, while the HFD-B pair potentials give much better agreement with the experimental values for 20NeAr2 and 22NeAr2 trimers.

S-wave resonances in the positron–helium scattering

We have performed a three-body calculation for investigation of S-wave resonances in the positron-helium scattering in the hyperspherical coordinates. B-splines are used to obtain accurate hyperspherical potential curves and channel functions. An adiabatical hyperspherical approach is used to predict semi-quantitatively the position of the resonances. A multichannel calculation with the stabilization method is also used to extract accurately the positions and widths of resonances. We find four resonances associated with the He(+)-Ps(n = 2) channel. The resonance parameters for the lowest two resonances are in reasonable agreement with the calculations of Kar and Ho (2004 J. Phys. B: At. Mol. Opt. Phys. 37 3177), and two more new resonances below the Ps(n = 2) threshold are identified.

The weakly bound states and resonances of the BeHe2 triatomic system

In the present study, we carry out a full search of the bound states and resonances of the He(2)Be triatomic system, with its isotopic variants (3)He(2)(9)Be, (3)He(4)He(9)Be, and (4)He(2)(9)Be using the hyperspherical method. Three-body long-range effects are also included in the computation by adding to the additive potential the Axilrod-Teller triple-dipole term. In addition, the possibility of the occurrence of Efimov-type states in these systems is discussed. We have found a bound state for each of the (3)He(2)(9)Be and (3)He(4)He(9)Be trimers, while one weakly bound excited state is also found to exist for the (4)He(2)(9)Be system.

Binding energy and geometry of e+A (A=Li,Na) by the hyperspherical approach

We calculate the binding energy and geometry of the weakly bound e(+)Li and e(+)Na systems within the framework of hyperspherical coordinates. The Schrodinger equation in hyperangular coordinates is solved at a series of fixed hyper-radii using B-splines and the resulting coupled hyper-radial equation is solved using the slow variable discretization method developed by Tolstikhin et al. [J. Phys. B 29, L389 (1996)]. Great efforts are made in optimizing the distribution of B-splines to overcome the slow convergence of the binding energy and geometrical quantities. This approach allows us to obtain the results with improved convergence that are in good agreement with the best values reported to date. In addition, an analysis of the structure of the two systems is also made and the e(+)Na system is seen to exhibit quantum halo features.

Structure and resonances of the e+?He(1s2s 3Se) system

We have studied the geometry and resonances of the e(+)He(S-3(e)) system in the framework of hyperspherical coordinates. A model potential proposed by us is used to describe the interaction between the out electron with the He+ ionic core. The calculated binding energy and expectation distance of the system are in agreement with other calculations. In addition, two resonances below the e(+)-He(1s3s S-3(e)) threshold and one resonance below the Ps(n=2)-He+ threshold are identified.

Hyperspherical coupled channel calculations of energy and structure of 4He–4He–Li+ and its isotopic combinations

The ground state vibrational energy and spatial features of (4)He-(4)He-Li(+) and its triatomic isotopic complexes are studied using the slow variable discretization (SVD) method in the hyperspherical coordinates for the zero total angular momentum. Our results show that the dominant structure of the system is an isosceles triangle with the shorter side associated with the two Li(+)-He distances using the sum-of-potential approximation. Corrections caused by the induced dipole-induced dipole interactions on the He atoms are also investigated. The effects are seen to be small and have a minor influence on the binding energy and the structure of present system. The results are also compared with the full ab initio calculations including all the three-body interactions and information of three-body corrections is obtained.

Statistical properties of the rovibrational bound levels for Ar2Kr

We calculate the rovibrational bound levels with total angular momentum J = 0, 1 of 40Ar284Kr trimer using the slow variable discretization method combined with the finite-element method-discrete variable representation basis. The statistical distributions of the rovibrational levels for JΠ=0e, 1e, and 1o symmetries are presented and the effects of the Axilrod-Teller potential term are considered. For the 0e and 1e symmetries, the Axilrod-Teller term makes the spectra become fully chaotic. However, for the 1o symmetry, statistical properties depend mainly on the coupling between K = 0 and K = 1 and the Axilrod-Teller term has a small effect.

Hyperspherical study of Ne2Kr and Ne2Xe systems

We have calculated the ground state energies and rotational constants for the Ne2Kr and Ne2Xe systems, as well as their corresponding isotopes using the hyperspherical method. We used B-splines as basis function to expand channel functions and make the knot distribution of B-splines characterize the behavior of the channel function precisely. As a result, the extremely slow convergence of quantum mechanic calculation for these van der Waals trimers containing heavy element is improved greatly. The convergent rotational constants and the isotope shifts are obtained and compared with other theoretical and experimental values. Our results using newly proposed Tang-Toennies (TT) pair-wise potentials are consistent with that of Ernesti and Hutson’s calculation using HFD-B potentials, and give an improved agreement with experimental data.