By introducing the concept of supersymmetry to quantum mechanics, several authors have shown that exactly soluble potentials, including all those well known, are easily constructed. Is the kinetic-energy density functional corresponding to these potentials a simple form? We show that the answer is no, even to the simplest one, the harmonic potential, if one builds the kinetic-energy density functional from the reduced density matrix.

Resonances in muonic systems tαμ and dαμ have been predicted for J=0 and 1 using the complex-rotation method. This method has the advantage that the resonance position and total width are calculated at the same time. These resonances are found to be below the n=4 threshold of αμ and are of Feshbach type. They decay to tμ+α and dμ+α, and therefore could be of importance in the reactivation of μ from αμ in the fusion of t and d in the presence of a muon (muon-catalyzed fusion). The channel (αμ${)}_{\mathit{n}=3\mathrm{}}$+t or d could be followed by multiple scattering, resulting in stripping of the muon. This process is highly density dependent.

In an effort to explain two disagreeing experimental measurements of photoionization cross sections, we employ an eigenchannel R-matrix approach using a jj-coupling basis set to calculate the photoionization of the excited state 6s6p ${}_{}{}^1{}_{}{}^{}$${\mathit{P}}_1$ of barium from threshold to about 3-eV photoelectron energy. The calculated cross section shows rich structure due to the breakdown of the LS coupling and mixing of several Rydberg series. Our results are in approximate agreement with one measurement farther from threshold, but indicate that the absolute normalization of another measurement at and around threshold is in error.

Continuum electron emission along the beam direction has been investigated in collisions of 60-keV ${\mathrm{O}}^{6+}$ ions with He. It is found that electron capture to the continuum is nearly always accompanied by bound-state capture, suggesting that ‘‘cusp’’ electrons originate in a two-electron process in these slow collisions.

Electron emission from clean gold under impact of ${\mathrm{H}}^{+}$ or singly charged rare-gas ions in their ground state has been investigated at the kinetic emission threshold, measuring both the emission statistics and total yields by means of counting techniques. As we are able to subtract any contribution from potential emission, we observe kinetic emission well below the threshold for sufficient energy transfer from projectiles onto quasifree metal electrons and relate this contribution to quasimolecular autoionization in close collisions between the neutralized projectiles and metal ion cores.

In a dense and cold laser-produced plasma the measured intensity of ${\mathrm{\alpha }}_2$→${\mathrm{\alpha }}_1$ transitions in highly ionized atoms may be strongly influenced by dielectronic satellites ${\mathrm{\alpha }}_2$nl→${\mathrm{\alpha }}_1$nl with a high value of the principal quantum number n of the ‘‘spectator’’ electron. This effect may be partially or fully responsible for the reported [Y. Chung, P. Lemaire, and S. Suckewer, Phys. Rev. Lett. 60, 1122 (1988); Y. Chung, H. Hirose, and S. Suckewer, Phys. Rev. A 40, 7142 (1989)] observation that the intensity branching ratio of lines depends on the parameters of the laser-produced plasma.

The quantum behavior of a hydrogen atom (with m=0) in a uniform magnetic field is mapped onto an asymmetric top. This mapping, in conjunction with the idea of a rotational energy surface, provides a physical interpretation for the observed electronic structure and quantum numbers, and gives an explanation for the localization of Rydberg states in a magnetic field.

We report on the spontaneous onset of temporal chaos in a waveguide ${\mathrm{CO}}_2$ laser due to the interaction between two transverse modes. A nonstandard configuration of the resonator has been used in order to obtain multitransverse mode operation. Starting from a mirror setting where two modes have a stable coexistence, further tiny variations of the cavity length induce a period-doubling cascade to chaos.

We present an alternative method for calculating energy-resolved properties from time-dependent wave functions. As a first application of the method, we calculate above-threshold ionization (ATI) spectra and energy-resolved angular distributions from hydrogen ionized by an intense, short-pulse laser at 532 nm. Below saturation the ATI peaks decrease according to an (intensity-dependent) power law. At the onset of saturation a plateau forms in the spectrum, reminiscent of plateaus seen experimentally in harmonic spectra observed during multiphoton ionization.

The influence of the atomic lifetimes on the photon statistics of the micromaser is discussed. The generation of trapping states and number states requires very-long-lifetime atoms in addition to low temperature.

We present a method for the calculation of multiphoton ionization, including above-threshold ionization and autoionization, which goes beyond the one-electron approximation. We illustrate the method with examples of calculations in He and Mg.

By modifying the phase formalism of Pegg and Barnett [Phys. Rev. A 39, 1665 (1989)], we illustrate the idea of Susskind and Glogower [Physics 1, 49 (1964)] concerning the zero uncertainty of their cosine and sine operators in the phase state.

We have developed a method for reconstructing equations of motion for systems where all the necessary variables have not been observed. This technique can be applied to systems with one or several such hidden variables, and can be used to reconstruct maps or differential equations. The effects of experimental noise are discussed through specific examples. The control of nonlinear systems containing hidden variables is also discussed.

We demonstrate how noise can be an effective tool in modeling systems whose experimental data sets would normally be limited to a small region of the reconstructed state space. In fact, for systems with stable fixed points, using noise to extend the accessible state-space volume may be the only possibility for constructing a model. We find that noise can also be useful in modeling limit cycles when multiple systems generate the same closed trajectory and the model that represents the true dynamics is desired. We discuss the implications of our method for nonlinear control theory about which important questions on the effects of noise in real-time modeling have arisen.

We have found that the regular motion of an integrable system becomes erratic when a weak white noise is added. The interaction between dynamic and stochastic forces gives rise to an erratic power spectrum, positive Lyapunov exponents, and nonzero correlation exponent independent of embedding dimensions. Since the weak noise drives the systems to unstable fixed points that the dynamic force cannot reach, we call the onset of this erratic behavior the noise-induced instability. The results also indicate that the nonzero correlation exponents independent of embedding dimensions are not necessarily related to the deterministic chaos and that caution should be used in applying this technique to distinguish chaos from noise.