The differential geometric background for the occurrence of SU(2) Berry phases in Fermi systems with time-reversal invariance is investigated. We explicitly construct the natural geometric structures on ${\mathrm{ssHssP}}^n$ (the quaternionic projective space) responsible for nontrivial holonomy. For the special case n=1, ${\mathrm{ssHssP}}^1$∼${\mathrm{ssS}}^4$, the connection that governs the time evolution corresponds to the SU(2) Yang-Mills instanton with self-dual curvature, giving the nonadiabatic generalization of the spin (3/2 case of Avron et al. [Phys. Rev. Lett. 61, 1329 (1988)].

The expectation value and variance of a new phase operator introduced recently by Pegg and Barnett [Europhys. Lett. 6, 483 (1988); Phys. Rev. A 39, 1665 (1989)] and by Barnett and Pegg [J. Mod. Opt. 36, 7 (1989)] is calculated for a coherent state. The values for the variance so obtained are compared with the phase-fluctuation measurements of Gerhardt, Büchler, and Liftin [Phys. Lett. 49A, 119 (1974)] and Gerhardt, Welling, and Frolich [Appl. Phys. 2, 91 (1973)]. Agreement is found to be good, provided that account is taken of the details of the experimental values.

Using hydrogenlike wave functions, a one-parameter, a two-parameter, and a four-parameter variational density-functional calculation of the total atomic binding energy of the Ne atom is carried out. The total-energy values, the radial electron (number) densities, together with values obtained for the electron (number) density at the nucleus, are compared with a previous three-parameter variational density-functional calculation and with the relevant single-ζ Hartree-Fock values. It is found that the magnitude of the total atomic binding energy converges to a limit as the number of variational parameters is increased from 1 to 4.

We present numerical results for the correction potential beyond the Coulomb-Breit and the Araki-Sucher interaction potentials due to transverse photon exchange between the Rydberg electron and the core in helium Rydberg atoms.

Some new corrections to the hydrogen Lamb shift from multiphoton exchange graphs have been calculated and found to be 1 kHz. Radiative corrections to the proton line have also been considered for diagrams containing two exchanged Coulomb interactions and have been found to be of the order of $Z^2$α(Zα${)}^5$$m^3$/$M^2$ and therefore negligible.

Using basis sets of random-tempered Slater-type geminals, we have calculated the nuclear fusion rates for the J=0,1 bound states of the mesomolecular ions xyμ(x,y=p,d,t).

We have measured the laboratory double-differential cross sections for electrons from the double ionization of 0.5-MeV ${\mathrm{H}}^{\mathrm{-}}$ in collisions with He. These data have been transformed into the projectile (${\mathrm{H}}^{\mathrm{-}}$) frame and the angular distributions of electrons (with a given energy in the projectile frame) were generated. It was found that, for all energies above 0.1 eV in the projectile frame, the angular distributions were anisotropic with a maxima at 0° and 180° and a minimum in between. We have also integrated these angular distributions over the solid angle and show an overall energy distribution of electrons produced by this double-ionization process.

Electric quadrupole and magnetic dipole transition probabilities for the 1$s^2$2$s^2$2$p^5$ ${}_{}{}^2{}_{}{}^{}P_{3/2}^o{}_{}{}^{}$ →1$s^2$2$s^2$2$p^{52}$$P_{1/2}^o$ fine-structure transition in the ${\mathrm{Si}}^{5+}$ ground-state term have been calculated, using configuration-interaction wave functions within the relativistic Breit-Pauli approximation. Next, electron-impact collision strengths for the ${}_{}{}^2{}_{}{}^{}\mathrm{P}_{3/2}^{\mathrm{o}}{}_{}{}^{}$${\mathrm{-}}^2$${\mathrm{P}}_{1/2}^{\mathrm{o}}$ transition have been calculated within a 16-state close-coupling approximation using the R-matrix method.

A quantum theory of a two-mode two-photon correlated spontaneous-emission laser is developed. It is shown that the quantum-noise quenching and even nonclassical effects can occur in both the average phase and relative amplitude of the two fields. Near threshold we find a maximum of 50% intracavity squeezing in the two-photon transition limit, with each of the average phase and the relative amplitude contributing 25% squeezing.

Transition energies and oscillator strengths of the ${\mathrm{ns}}^2$ ${}_{}{}^1{}_{}{}^{}\mathrm{S}_0^{}{}_{}{}^{}$–nsnp ${}_{}{}^3{}_{}{}^{}\mathrm{P}_1^{}{}_{}{}^{}$${,}^1$${\mathrm{P}}_1$ transitions in Zn i, Rb viii, Hg i, and Rn vii spectra obtained for short basis sets with multiconfigurational Dirac-Fock ‘‘optimal-level’’ [MCDF(OL)] and ‘‘average-level’’ [MCDF(AL)] as well as with relativistic configuration-interaction (CIDF) methods are compared with experimental data. It can be seen that for highly ionized systems all three methods yield very close results, whereas for neutral systems the MCDF(OL) method is the most reliable. For neutral systems and short basis sets the MCDF(AL) results differ considerably with experiment and are very similar to those of the CIDF approach. This dfference is largely reduced if core-electron–valence-electron correlation is included in the core-polarization approximation.

We report a measurement of the rate constant for associative ionization (AI) between excited Na(3p) atoms colliding within a single beam at a velocity of 11.9 ${\mathrm{msec}}^{\mathrm{-}1}$, corresponding to a temperature of 65 mK. The collisions take place in a narrow velocity class of excited atoms produced by crossing the collimated Na beam with a monomode dye laser at an angle of 45°. Light polarized linearly in the collision plane yields an AI rate constant greater than that for circular polarization by a factor of 2. We find $K_{65\mathrm{m}\mathrm{K}{}^{\mathrm{lin}}}$ =(12.2±4.3)×${10}^{\mathrm{-}13}$ ${\mathrm{cm}}^3$ ${\sec }^{\mathrm{-}1}$ and $K_{65\mathrm{m}\mathrm{K}{}^{\mathrm{cir}}}$ =(6.1±1.8)×${10}^{\mathrm{-}13}$ ${\mathrm{cm}}^3$ ${\sec }^{\mathrm{-}1}$. The experimental arrangement also permits absolute calibration of earlier crossed-beam measurements of the excitation function (cross section versus velocity) at conventional thermal beam kinetic energies. Present results together with earlier work show that the cross-sectional temperature dependence is in qualitative accord with theory.

Analysis of the synchrotron-betatron coupling in a free-electron laser indicates that the particle motion is susceptible to an instability that is of a fundamentally different physical character to those examined previously. The domain of this instability, which is of a parametric type and causes an exponential growth of the betatron amplitude, is identified, and the growth rate therein determined.

The exponential index K in the Na 3s-5s two-photon transition as a function of detuning in the range from -186 to 172 GHz was experimentally investigated. The value of the K index varies from 2.0 to 1.6 and from 1.9 to 0.41 for the pumping intensities of 3.5 and 14 MW/${\mathrm{cm}}^2$, respectively; they agree well with the theoretical prediction obtained from the optical Bloch equations.

Optical phase conjugation by degenerate four-wave mixing has been achieved in the cw regime in liquid suspensions of polymer microellipsoids. The results clearly show that particle-number-density gratings and orientational gratings are generated within the suspensions over different ranges of the excitation frequency depending upon the beam polarization configuration and the host-liquid viscosity. The measured parameters are in good agreement with a classical model based on light-induced particle diffusive rearrangements.

The emission spectrum of strongly driven two-level atoms in a cavity is calculated outside the adiabatic approximation; i.e., the ratio of the cavity resonance width to the atomic natural linewidth is left arbitrary. This nonadiabaticity changes the character of the spectrum in a significant way.

Following the lines sketched by Kujawski [Phys. Rev. A 37, 1386 (1988)] for the semiclassical version of the Jaynes-Cummings model without the rotating-wave approximation, we have obtained an alternative analytic periodic solution given in terms of elliptic functions. We discuss domains of values of the coupling constant and the detuning for which known yet exact periodic solutions exist.

It is shown that the minimal coupling interaction and the multipolar interaction -μ⋅E give identical predictions for the second-order susceptibility. This contrasts with differing results obtained by Hammond [R. T. Hammond, Phys. Rev. A 39, 2544 (1989)]. The unique answer is obtained in the most straightforward way from the multipolar Hamiltonian. Complicated sum rules are needed to demonstrate the correct result from the minimal coupling form of the interaction.

We show that a result derived previously by Lami and Rahman [Phys. Rev. A 34, 3908 (1986)] whereby bound states can be created in a continuum, contains an algebraic error. We present the correction and discuss some implications.

It is recognized that the preceding Comment by Glosson and Cantrell [Phys. Rev. A 41, 2898 (1990)] corrects an algebraic error present in our two previous papers [Lami and Rahman, Phys. Rev. A 33, 782 (1986); 34, 3908 (1986)] (concerning a nonessential point). A few comments are added on the problem of generation of bound states in the continuum through electromagnetic fields.