Shi Ting-Yun

Variational calculations for a hydrogen atom confined off-centre in an impenetrable spherical box using B-splines

We have calculated the energy levels of a hydrogen atom confined off-centre in an impenetrable spherical box using a linear variational method. Both the radial and angular wavefunctions are expanded in terms of B-splines. The validity of the approach has been examined for various off-centre distances. Comparison with other results given in the literature is made and consistent agreement is achieved. The change of the features of the energy levels in accord with the off-centre distance is revealed.

Energy spectra of the confined atoms obtained by using B-splines

We have calculated the energy spectra of one- and two-electron atoms (ions) centered in an impenetrable spherical box by variational method with B-splines as basis functions. Accurate results are obtained for both large and small radii of confinement. The critical box radius of confined hydrogen atom is also calculated to show the usefulness of our method. A partial energy degeneracy in confined hydrogen atom is found when the radius of spherical box is equal to the distance at which a node of single-node wavefunctions of free hydrogen atom is located.

Relativistic Quadrupole Polarizability for the Ground State of Hydrogen-Like Ions

The static quadrupole polarizabilities for hydrogen-like ions from Z = 1 to Z = 100 in the 1S(1/2) ground state are calculated to high precision by solving the Dirac equation using the B-spline Galerkin method. The results are consistent with the expression of Kaneko [J. Phys. B 10 (1977) 3347] at low Z. The quadrupole oscillator strength sum Sigma(n) f(gn)((2)) is computed to be zero to a very high degree of precision.

H+2-Like Impurities Confined by Spherical Quantum Dots: a Candidate for Charge Qubits

We have calculated the electron energy of the ground and lower excited states for H-2(+)-like impurity states confined in finite spherical quantum dots in GaAs. Based on the characteristics of energy levels, we have proposed a scheme for realizing charge qubit composed by the the ground and the first excited states of this confined double donor system for the first time. In the proposed scheme the charge qubit is coded in terms of the located electronic states.

Effect of electron correlation on high-order harmonic generation in helium model atom

High-order harmonic generation (HHG) of a helium model atom in an intense laser field has been numerically investigated. The influence of electron correlation on HHG is analysed by changing the strength between the electrons. The numerical results show that as the electron interaction strength becomes small, the first ionization energy increases rapidly, which results in the decrease in ionization. So the conversion efficiency of the high harmonic lying in the plateau decreases greatly, while the cutoff harmonic order in the harmonic spectrum increases.

High-precision spectroscopy of hydrogen molecular ions

In this paper, we overview recent advances in high-precision structure calculations of the hydrogen molecular ions (H-2(+) and HD+), including nonrelativistic energy eigenvalues and relativistic and quantum electrodynamic corrections. In combination with high-precision measurements, it is feasible to precisely determine a molecular-based value of the protonto-electron mass ratio. An experimental scheme is presented for measuring the rovibrational transition frequency (v, L) : (0,0) -> (6,1) in HD+, which is currently underway at the Wuhan Institute of Physics and Mathematics.

Precision calculation of fine structure in helium and Li

The fine structure constant a can be extracted from high-precision spectroscopy of the 2(3)P(J) fine structure splittings in helium and light helium-like ions. In this work, the 23PJ fine structure splittings of helium and Li+ ion are calculated, including relativistic and QED corrections of order m alpha(4), m alpha(4) (m/M), m alpha(5), m alpha(5) (m/M), and Douglas-Kroll operators of m alpha(6) and m alpha(6) (m/M), which provide an independent verification for the previous calculations performed by Drake [Can. J. Phys. 80 1195 (2002)] and by Pachucki and Yerokhin [Phys. Rev. A 79 062516 (2009); Phys. Rev. Lett. 104 070403 (2010); Can. J. Phys. 89 1139 (2011)]. The results of the three groups agree with each other.

Alignment-Dependent Ionization of CO2 in the Intense Laser Fields: Single-Active-Electron Approach

We perform Hartree-Fock calculations to obtain occupied orbitals for triatomic molecule CO2, based on one-center method and B-splines to deal with cusps and speed up convergence. Both the orbital energies and charge distribution are in good accordance with the reference data. The valence orbital is propagated with single-active-electron approximation, and the alignment-dependent ionization yield peaks about 40 degrees. However, there are discrepancies between our results and the experimental data, and many-electron effects may need to be exploited further to describe them.

The Hydrogen Molecular Ion in Strong Fields Using the B-Spline Method

An accurate method combining the spheroidal coordinate and B-spline for H-2(+) 2 is tested. The equilibrium distances and the total energies of the states with vertical bar m vertical bar <= 4 for the magnetic field strength gamma = 1 are given and compared with those obtained using different methods. Taking the advantages of the spheroidal coordinate and B-spline, a 10(-9)-10(-12) accuracy is obtained for the energies of the states with vertical bar m vertical bar <= 3, and a 10(-5)-10(-7) accuracy for the equilibrium distances. There are seven significant digits for the energy of the state 1 gamma(g) and four significant digits for 1 gamma(u), which are consistent with those obtained by the high-precision method. There are three significant digits for the equilibrium distances of the 1 gamma(g,u) states, which are consistent.

Static Dipole Polarizabilities for Low-Lying Rovibrational States of HD+*

Accurate calculations are performed for the static dipole polarizabilities of HD+ in the rovibrational states with both of the vibrational and angular momentum quantum numbers nu and L from 0 to 5, by using variationally generated wavefunctions in Hylleraas coordinates. Comparison is made with recently published results. Significant improvements are achieved for the angular momentum quantum number L > 0 excited states by including another independent block to optimize meticulously the intermediate states of unnatural parity.