Li-Yan Tang

The long-range non-additive three-body dispersion interactions for the rare gases, alkali, and alkaline-earth atoms.

The long-range non-additive three-body dispersion interaction coefficients Z(111), Z(112), Z(113), and Z(122) are computed for many atomic combinations using standard expressions. The atoms considered include hydrogen, the rare gases, the alkali atoms (up to Rb), and the alkaline-earth atoms (up to Sr). The term Z(111) arising from three mutual dipole interactions is known as the Axilrod-Teller-Muto coefficient or the DDD (dipole-dipole-dipole) coefficient. Similarly, the terms Z(112), Z(113), and Z(122) arise from the mutual combinations of dipole (1), quadrupole (2), and octupole (3) interactions between atoms and they are sometimes known, respectively, as dipole-dipole-quadrupole, dipole-dipole-octupole, and dipole-quadrupole-quadrupole coefficients. Results for the four Z coefficients are given for the homonuclear trimers, for the trimers involving two like-rare-gas atoms, and for the trimers with all combinations of the H, He, and Li atoms. An exhaustive compilation of all coefficients between all possible atomic combinations is presented as supplementary data.

Nonrelativistic ab initio calculations for 2 S-2, 2 P-2, and 3 D-2 lithium isotopes: Applications to polarizabilities and dispersion interactions

The electric dipole polarizabilities and hyperpolarizabilities for the lithium isotopes Li-6 and Li-7 in the ground state 2 S-2 and the excited states 2 P-2 and 3 D-2, as well as the leading resonance and dispersion long-range coefficients for the Li(2 S-2)-Li(2 S-2) and Li(2 S-2)-Li(2 P-2) systems, are calculated nonrelativistically using variational wave functions in Hylleraas basis sets. Comparisons are made with published results, where available. We find that the value of the second hyperpolarizability of the 2 S-2 state is sensitive to the isotopic mass due to a near cancellation between two terms. For the 3 D-2 state polarizability tensor, the calculated components disagree with those measured in the sole experiment and with those calculated semiempirically.

Tune-out wavelengths for potassium

The five longest tune-out wavelengths for the potassium atom are determined using a relativistic structure model which treats the atom as consisting of a single valence electron moving outside a closed shell core. The importance of various terms in the dynamic polarizability in the vicinity of the 4p(J), 5p(J), and 6p(J) transitions are discussed. DOI: 10.1103/PhysRevA.87.032518

Oscillator strengths between low-lying ro-vibrational states of hydrogen molecular ions

It is important for experimental design to know the transition oscillator strengths in hydrogen molecular ions. In this work, for HD(+), HT(+), and DT(+), we calculate the ro-vibrational energies and oscillator strengths of dipole transitions between two ro-vibrational states with the vibrational quantum number ν = 0-5 and the total angular momentum L = 0-5. The oscillator strengths of HT(+) and DT(+) are presented as supplementary material.

Computational investigation of static multipole polarizabilities and sum rules for ground-state hydrogenlike ions

High-precision multipole polarizabilities, alpha(l) for l <= 4 of the 1s ground state of the hydrogen isoelectronic series, are obtained from the Dirac equation using the B-spline method with Notre Dame boundary conditions. Compact analytic expressions for the polarizabilities as a function of Z with a relative accuracy of 10(-6) up to Z = 100 are determined by fitting to the calculated polarizabilities. The oscillator strengths satisfy the sum rules Sigma(i) f(gi)((l)) = 0 for all multipoles from l = 1 to l = 4. The dispersion coefficients for the long-range H-H and H-He+ interactions are given.

Dynamic dipole polarizabilities of the Li atom and the Be + ion

The dynamic dipole polarizabilities for Li atoms and Be+ ions in the 2(2)S and 2(2)P states are calculated using the variational method with a Hylleraas basis. The present polarizabilities represent the definitive values in the nonrelativistic limit. Corrections due to relativistic effects are also estimated. Analytic representations of the polarizabilities for frequency ranges encompassing the n = 3 excitations are presented. The recommended polarizabilities for Li-7 and Be-9(+) are 164.11 +/- 0.03 a(0)(3) and 24.489 +/- 0.004 a(0)(3), respectively.

Convergence of the multipole expansions of the polarization and dispersion interactions for atoms under confinement

The multipole expansion of the polarization interaction between a charged particle and an electrically neutral object has long been known to be asymptotic in nature, i.e., the multiple expansion diverges at any finite distance from the atom. However, the multipole expansion of the polarization potential of a confined hydrogen atom is shown to be absolutely convergent at a distance outside the confinement radius, R(0), of the atom. The multipole expansion of the dispersion potential between two confined hydrogen atoms is also shown to be absolutely convergent provided the two atoms satisfy R > 2R(0), where R is the inter-nuclear separation. These results were established analytically using oscillator strength sum rules and verified numerically using a B-spline description of the hydrogen ground state and its excitation spectrum.

High-precision nonadiabatic calculations of dynamic polarizabilities and hyperpolarizabilities for low-lying vibrational-rotational states of hydrogen molecular ions

The static and dynamic electric multipolar polarizabilities and second hyperpolarizabilities of the H-2(+), D-2(+), and HD+ molecular ions in the ground and first excited states are calculated nonrelativistically using explicitly correlated Hylleraas basis sets. The calculations are fully nonadiabatic; the Born-Oppenheimer approximation is not used. Comparisons are made with published theoretical and experimental results, where available. In our approach, no derivatives of energy functions nor derivatives of response functions are needed. In particular, we make contact with earlier calculations in the Born-Oppenheimer calculation where polarizabilities were decomposed into electronic, vibrational, and rotational contributions and where hyperpolarizabilities were determined from derivatives of energy functions. We find that the static hyperpolarizability for the ground state of HD+ is seven orders of magnitude larger than the corresponding dipole polarizability. For the dipole polarizability of HD+ in the first excited state the high precision of the present method facilitates treatment of a near cancellation between two terms. For applications to laser spectroscopy of trapped ions we find tune-out and magic wavelengths for the HD+ ion in a laser field. In addition, we also calculate the first few leading terms for long-range interactions of a hydrogen molecular ion and a ground state H, He, or Li atom.

Long-range dispersion coefficients for Li, Li + , and Be + interacting with the rare gases

The long-range dispersion coefficients for the ground and excited states of Li, Li(+), and Be(+) interacting with the He, Ne, Ar, Kr, and Xe atoms in their ground states are determined. The variational Hylleraas method is used to determine the necessary lists of multipole matrix elements for He, Li, Li(+), and Be(+), while pseudo-oscillator strength distributions are used for the heavier rare gases. Some single electron calculations using a semiempirical Hamiltonian are also performed for Li and Be(+) and found to give dispersion coefficients in good agreement with the Hylleraas calculations. Polarizabilities are given for some of the Li and Li(+) states and the recommended (7)Li(+) polarizability including both finite-mass and relativistic effects was 0.192 486 a.u. The impact of finite-mass effects upon the dispersion coefficients has been given for some selected interatomic interactions.

Calculations of polarizabilities and hyperpolarizabilities for the Be+ ion

The polarizabilities and hyperpolarizabilities of the Be+ ion in the 2 S-2 state and the 2 P-2 state are determined. Calculations are performed using two independent methods: (i) variationally determined wave functions using Hylleraas basis set expansions and (ii) single electron calculations utilizing a frozen-core Hamiltonian. The first few parameters in the long-range interaction potential between a Be+ ion and a H, He, or Li atom, and the leading parameters of the effective potential for the high-L Rydberg states of beryllium were also computed. All the values reported are the results of calculations close to convergence. Comparisons are made with published results where available.