Precision Spectroscopy of the Pionic Helium-4.

The transition frequency of (n,ℓ)=(17,16)→(16,15) in pionic helium-4 is calculated to an accuracy of 4 ppb (parts per billion), including relativistic and quantum electrodynamic corrections up to O(R_{∞}α^{5}). Our calculations significantly improve the recent theoretical values [Hori et al., Phys.

Precision Calculation of Hyperfine Structure and the Zemach Radii of ^{6,7}Li^{+} Ions.

The hyperfine structures of the 2^{3}S_{1} states of the ^{6}Li^{+} and ^{7}Li^{+} ions are investigated theoretically to extract the Zemach radii of the ^{6}Li and ^{7}Li nuclei by comparing with precision measurements. The obtained Zemach radii are larger than the previous values of Puchalski and Pachucki [Phys. Rev.

Relativistic corrections to the ground states of HD and D calculated without using the Born-Oppenheimer approximation.

The Schrödinger equation for the ground states of the hydrogen molecules HD and D is solved variationally by treating the constituent particles of HD or D on the same footing without assuming the Born-Oppenheimer approximation. The variational basis sets are constructed using Hylleraas coordinates that are traditionally adopted for few-electron atomic systems. The nonrelativistic energy eigenvalues are converged to the level of 10 cm.

Fine structure and ionization energy of the 1s2s2p 4P state of the helium negative ion He-.

The fine structure and ionization energy of the 1s2s2p (4)P state of the helium negative ion He(-) are calculated in Hylleraas coordinates, including relativistic and QED corrections up to O(α(4)mc(2)), O((μ/M)α(4)mc(2)), O(α(5)mc(2)), and O((μ/M)α(5)mc(2)). Higher order corrections are estimated for the ionization energy. A comparison is made with other calculations and experiments.

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.

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.

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.

Carrier-envelope phase dependence of non-sequential double ionization in few-cycle pulses.

The influence of carrier-envelope phase (CEP) of a few-cycle laser pulse on non-sequential double ionization (NSDI) of an atom is investigated by applying the three-dimensional semi-classical re-scattering method. The asymmetric momentum distribution of the double-charged ion parallel to the laser polarization, which depends on the CEP, is explained by comparing the contributions from several half-cycles in the laser pulse. The ionization rate and the returning kinetic energy of the first electron dramatically affect the contributions from each half-cycles, and play different roles in different laser intensity regimes.

Bethe logarithm and QED shift for lithium.

A novel finite basis set method is used to calculate the Bethe logarithm for the ground 2 (2)S(1/2) and excited 3 (2)S(1/2) states of lithium. The basis sets are constructed to span a huge range of distance scales within a single calculation, leading to well-converged values for the Bethe logarithm. The results are used to calculate an accurate value for the complete quantum electrodynamic energy shift up to order alpha(3) Ry.