In a recent paper, Chaudhuri and Mondal [Phys. Rev. A 43, 3241 (1991)] have reported an improved Hill determinant method for the calculation of the eigenvalues of general quantum anharmonic oscillators. However, the accuracy of their calculations is restricted by their use of a nonrecursive matrix diagonalization scheme. We show how considerably greater accuracy can be achieved by the use of tridiagonal vector recurrence relations.

A general procedure for calculating the gauge-invariant, nonadiabatic, geometric phase, and dynamic phase of a quantum system in a classical electromagnetic field is outlined. Exact numerical results for an electron in a potential well are presented and analyzed.

In the method of exterior complex scaling the coordinates of the Hamilton operator are scaled by a constant factor starting at a radius R≠0. We show that this procedure induces a singularity in the kinetic-energy term which must be interpreted as the derivative of a δ function.

It is shown that the condition required for one of the potentials considered by Dutra [Phys. Rev. A 47, R2435 (1993)] to be a conditionally exactly soluble potential is the same as that the potential can be put in an explicitly supersymmetric form.

Following closely a technique due to Lieb [Phys. Rev. Lett. 52, 315 (1984)], a rigorous condition for an atom-positron bound state is derived in terms of the electrostatic Coulomb attractive potential between the positron and the atomic electrons. Further, it is demonstrated that for a joint electron-positron pair density distribution that is spherically symmetric around the nucleus in the positron and/or the electron coordinate, a bound state between a neutral atom and a positron is not possible.

We present a procedure for the calculation of dynamic polarizabilities and we obtain numerical values of the dynamic polarizabilities of rubidium to compare with recent measurements at the frequency of the Nd:YAG (neodymium-doped yttrium aluminum garnet) laser at 1064 nm. We obtain at 1064 nm a polarizability of 711.4${\mathit{a}}_0^3$ compared to the measured value of (769±61)${\mathit{a}}_0^3$.

The possibility for a self-conjugate system such as positronium to have a T-odd, P-even quadrupole toroidal moment is discussed. It is shown that the positronium quadrupole toroidal moment is different from zero if we assume that the T-odd, P-even electron-positron interaction is mediated by a light axial boson with mass μ (μ≤αm m is the electron mass). In the case of a heavy mediating boson the quadrupole toroidal moment of positronium is shown to vanish.

The potential-energy curves and couplings of the ${}_{}{}^{2,4}{}_{}{}^{}\mathrm{\Sigma }$ and ${}_{}{}^{2,4}{}_{}{}^{}\mathrm{\Pi }$ states involved in the collision of the metastable ${\mathrm{B}}^{3+}$(1s2s) multicharged ion on atomic hydrogen have been calculated by means of an ab initio method with configuration interaction. The collision processes have been examined, and the electron-capture cross sections have been determined by means of a semiclassical method.

In view of controversial discussions in the literature concerning the charge-state dependence of the binary encounter maximum, we reexamined our early experiments of cross sections for electron emission at 25° in 30-MeV ${\mathrm{O}}^{\mathit{q}+}$+${\mathrm{O}}_2$ collisions. Analyzing KLL target Auger peaks in the electron spectra, we revised our previous data for the projectile charge state q=8 whereas the data for q=4–7 are essentially confirmed. Hence, the binary encounter maximum is found to increase with an increasing charge state of q=4–7 and it decreases from q=7–8.

Total and partial photoionization cross sections of positive He-like ions in their ground states have been evaluated in the vicinity of the 3(1,1${)}_3$ ${}_{}{}^1{}_{}{}^{}$${\mathit{P}}^0$ (‘‘3s3p’’) doubly excited state for nuclear charges ranging from Z=2 to Z=18. We observe an apparent cancellation of the Fano interferences for Z≃4–5, which results in the presence of almost Lorentzian peaks in the photoabsorption spectrum. The origin of this cancellation and the behavior of the Fano and the Starace parameters along Z are discussed.

Double-photoionization cross sections are calculated for two-electron targets ${\mathrm{H}}^{\mathrm{-}}$, He, ${\mathrm{Li}}^{+}$, and ${\mathrm{O}}^{6+}$ using a correlated and an uncorrelated two-electron continuum wave function (C3 and C2 models, respectively). As the target nuclear charge ${\mathit{Z}}_{\mathit{T}}$ is increased, the double-photoionization cross section is found to scale as ${\mathit{Z}}_{\mathit{T}}^{\mathrm{-}4}$ and the electron energy distribution as ${\mathit{Z}}_{\mathit{T}}^{\mathrm{-}6}$. Conclusions are extracted about the behavior of the cross sections in the high-energy and threshold regions. The ratio of double to single photoionization scales as ${\mathit{Z}}_{\mathit{T}}^{\mathrm{-}2}$, as in the case of proton impact.

Auger decay of the Kr 3${\mathit{d}}^{\mathrm{-}1}$4${\mathit{p}}^{\mathrm{-}1}$ and Xe 4${\mathit{d}}^{\mathrm{-}1}$5${\mathit{p}}^{\mathrm{-}1}$ states created by shake off transitions during photoionization has been studied using synchrotron-radiation excitation. The Auger transitions to the final states 4${\mathit{p}}^{\mathrm{-}3}$ in Kr and 5${\mathit{p}}^{\mathrm{-}3}$ in Xe have been interpreted by comparing recorded spectra with semiempirical predictions obtained with the aid of multiconfiguration Dirac-Fock calculations.

The dc Stark shift of the D1 lines of rubidium and potassium are observed using a pair of cavity-stabilized diode lasers locked to resonance signals. The heterodyne signal from the two lasers and the optical measurements of the electrode spacing yield high-precision results. The observed scalar shifts are found to be 61.153(8) kHz (kV/cm${)}^{\mathrm{-}2}$ for rubidium and 39.400(5) kHz (kV/cm${)}^{\mathrm{-}2}$ for potassium. These results represent more than three orders of magnitude improvement in our knowledge of these Stark shifts.

The nonadiabatic geometric phase for an arbitrary cyclic evolution of the state vector for a system described by the quantum theory of the propagation of a single-mode off-resonant field through the dispersive fiber is discussed here. The sensitivity of the geometric phase on the initial field statistics has been explicitly shown in the calculations. We also derive the expressions of the geometric phase when the system is prepared initially in a squeezed coherent state.

In a time-dependent dressed-state calculation we have studied the time development of (1+1)-photon amplification without population inversion from an autoionizing (AI) state which is coupled to another AI state embedded into the same continuum. We have shown that the (1+1)-photon gain evolves with time over the single-photon gain and it can be controlled by changing the relative strength of the coupling of the resonant intermediate state with the ground state and with the two AI states. We have also shown that three-peaked gain on the upper probe field evolves with time and we have demonstrated that the modification of the second peak and the appearance of the third peak are solely due to the presence of the second AI state.

Exact analytical expressions for quantum revivals in an optical fiber with a Kerr nonlinearity are obtained. It is found that the revival amplitudes are much smaller than those predicted earlier by the Hartree approximation.

Based on a master equation method, a two-photon laser is modeled as a single noninverted three-level atom interacting via a two-photon transition with a single resonant-cavity field mode. The laser exhibits the bistability switching between vacuum and lasing states in the high pump power without injected signal. Such a feature is accompanied by intensity-noise quenching and lasing without inversion. The bistability is forbidden in a similar ordinary laser—a Raman laser.

A wave-function approach to the interaction Hamiltonian for the degenerate parametric amplifier has been recently presented [C. G. Bollini and L. E. Oxman, Phys. Rev. A 47, 2339 (1993)]. We want to show here that a maximum entropy principle density matrix approach can be used to reobtain all the results shown in this reference, and also to avoid the use of a nonproperly continuous generalization of the Shannon discrete entropy.

We show that both super-Poissonian and sub-Poissonian photo statistics may be modeled by the use of the recently introduced M-type q-deformed coherent states, while P-type q-deformed coherent states exhibit nonclassical sub-Poissonian photon statistics. Applications to the characterization of the photon statistics of laser outputs reasonably close to threshold, single-atom resonance fluorescence, the micromaser field, and absorption by two-level atoms are considered.

Zhao and Parr [Phys. Rev. A 46, R5320 (1992)] recently introduced an exchange-correlation functional for the local-density approximation of the density-functional theory. In this paper we report results for aotms, molecules, and crystalline solids using their functional as well as traditional ones. We conclude that their functional yields a better description of neither the ionization energies nor of the chemical bond in polyatomic systems.