This paper presents an x-ray laser mechanism that uses radiation trapping of the strongest 3${\mathit{d}}^1$${\mathit{P}}_1$→2${\mathit{p}}^1$${\mathit{S}}_0$ neonlike resonance line in an optically thick plasma to create an intense radiation field that radiatively drives population from the neonlike ground state to the 3${\mathit{d}}^1$${\mathit{P}}_1$ state, which then lases to the 3${\mathit{p}}^1$${\mathit{P}}_1$ and 3${\mathit{p}}^3$${\mathit{P}}_1$ states. Collisional mixing of the 3p states with nearby 3s and 3d states depopulates the lower laser states. Modeling is presented for this mechanism in neonlike argon. Strong gain is predicted on the two 3d→3p transitions at 451 and 465 Å, the first of which has been observed in recent x-ray laser experiments using an argon gas puff. This pumping mechanism also enhances the population of the 3${\mathit{p}}^1$${\mathit{S}}_0$ state and the gain of the two 3p→3s, J=0→1 transitions, which are at 431 and 469 Å in argon. © 1996 The American Physical Society.

Two related methods for determining the Lorentzian linewidth of one- and two-photon transitions in an atomic medium are presented. In each method, the linewidth is determined by the relationship between the energy transmission and propagation delay of a series of laser pulses sent through the medium; precise knowledge of the laser frequency, atom density, or matrix elements is not required. © 1996 The American Physical Society.

A theory of two-photon down-conversion in the presence of mirrors is developed and applied to recent observations of Herzog et al. [Phys. Rev. Lett. 72, 629 (1994)]. The experimentally observed results for counting and coincidence rates as functions of mirror-crystal separations are obtained, and it is shown how the same results may be derived in a simplified formulation that presumes phase-matched signal and idler modes. We account for the observed effects of the finite coherence length of the pump field as well as the signal and idler coherence lengths, which are much shorter than the pump coherence length and have a different physical origin. Our analysis also supports the interpretation of the phenomena observed as being analogous to the modification of single photon spontaneous emission of atoms in cavity QED. © 1996 The American Physical Society.

A quantization scheme for the electromagnetic field in absorbing dielectrics developed previously is extended to cover more complicated arrangements of dielectric media and to investigate various limiting cases of the general formalism. The limiting cases include media that have vanishing imaginary parts in their dielectric functions, because either the refractive index or the extinction coefficient vanishes. The further limit of a unit real dielectric function establishes the connection of the formalism with the well-known quantized field expressions in free space. Detailed calculations are presented for the quantization in the system of two different absorbing dielectrics in contact at a plane interface and for the cavity formed in the free space between two separated absorbing dielectrics. The forms of the field operators are determined for both systems, the canonical commutation relations are verified, and the spectra of the vacuum field fluctuations are calculated and illustrated. The calculations are restricted throughout to fields that propagate perpendicular to the dielectric interfaces. © 1996 The American Physical Society.

We study a model of single-photon nonlocality in which two separated cavities are prepared in an entangled state containing only one photon. The nonlocality is then transferred to two atoms probing each cavity. When the atoms are subsequently analyzed by classical microwave fields and selective ionization, Bell’s inequalities are found to be violated for a wide range of atomic velocities. © 1996 The American Physical Society.

We show that a Young’s N-slit interferometer can be used to factor the integer N. The device could factor four- or five-digit numbers in a practical fashion. This work shows how number theory may arise in physical problems, and may provide some insight as to how quantum computers can carry out factoring problems by interferometric means. © 1996 The American Physical Society.

I propose a method to prepare four atoms in an entangled state of the type discussed by Greenberger, Horne, and Zeilinger [in Bell’s Theorem, Quantum Theory and Conceptions of the Universe, edited by M. Kafatos (Kluwer Academic, Dordrecht, 1989), p. 107]. The method involves two micromaser cavities, each supporting two modes initially prepared in a nonlocalized two-photon state by an atom undergoing a two-photon transition. Subsequently, two atoms pass through each cavity, becoming entangled in a Greenberger-Horne-Zeilinger state leaving the cavities in the vacuum. © 1996 The American Physical Society.

We have measured the isotropic collision-induced light-scattering spectrum of a metal vapor, i.e., mercury vapor at temperature T=973 K and densities around 0.113 atom/${\mathrm{nm}}^3$, by means of an apparatus which allows us to perform comparisons between polarized and depolarized Raman spectra in high-temperature high-pressure gases and metal vapors. We have then derived an empirical model for the collision-induced polarizability trace of mercury diatom. Similarly to the anisotropy, the obtained trace behaves rather differently from the noble-gas counterpart, showing strong contributions from the electron correlations in the overlap region. © 1996 The American Physical Society.

The adiabatic nuclear rotation (ANR) model has been employed to obtain rotational excitation cross sections for electronically elastic and electronic excitation processes in ${\mathit{e}}^{+}$-${\mathrm{H}}_2$ scattering. The present results are compared with the more accurate laboratory-frame rotational close-coupling approximation (LFCCA) predictions. The electronically inelastic rotational excitation results using the ANR model differ from the corresponding LFCCA results near the electronic excitation threshold energies. © 1996 The American Physical Society.

In a paper with the title given above, Garbaczewski and Olkiewicz [Phys. Rev. A 51, 3445 (1995)] claim that a contrarily entitled paper of Gillespie [Phys. Rev. A 49, 1607 (1994)] is misleading because it is based on an allegedly overly restrictive assumption. In the discussion given here of that claim, the impugned assumption, and some foundational aspects of Markovian and non-Markovian stochastic processes, it is concluded that the thesis of the later title has not been established.

In this paper the phase-invariant clock hypothesis for accelerating systems suggested by F. V. Kowalski [Phys. Rev. A 46, 2261 (1992)] is investigated in detail. It is pointed out that in Kowalski’s derivation of the most distinctive result of the hypothesis, predicting no frequency shift between two spatially separated clocks rigidly accelerating, there are a few points needing further discussion. In addition, it is shown that the generalized phase-invariant clock hypothesis denies the existence of the usual twin paradox. © 1996 The American Physical Society.

A response is given to the work of Guangda et al. in which they criticize the paper ‘‘Phase Invariant Clock Hypothesis.’’ © 1996 The American Physical Society.

Recently, Le Sech [Phys. Rev. A 51, R2668 (1995)] presented results of variational computations of electronic energies for some two-electron diatomic-molecular ions. These energies, obtained with a very simple wave function, are, for some internuclear distances, lower than ever reported. We claim that these results are incorrect. © 1996 The American Physical Society.

Controversial points in the preceding Comment [L. Wolniewicz, Phys. Rev. A 53, 4609 (1996)] about the X${\mathrm{}}^1$${\mathrm{\Sigma }}_{\mathit{g}}$ state of ${\mathrm{He}}_2^{2+}$ are clarified. We confirm the previous results obtained with a very simple wave function. © 1996 The American Physical Society.

A recent theoretical treatment of intermolecular nuclear-spin relaxation that incorporates the effect of molecular rotation [K. Lendi, Phys. Rev. A 45, 7906 (1992)] is shown to be based on what appears to be a mistaken assignment of Euler angles. In particular, the conditional probability for reorientation of the intermolecular vector due to molecular rotation seems to be given incorrectly. Unsolvable integrals that are examined by Lendi are derived without considering the reflecting wall boundary conditions that are requisite for the problem of translational diffusion. © 1996 The American Physical Society.

It is argued that my choice of coordinate systems does not affect expectation values and is particularly suited for the factorizarion of stochastic processes implying independent simultaneous translation and rotation. By this procedure the compact and rigorous results due to Dale Favro can be built in from the very beginning. The criticized boundary conditions [see preceding Comment, Skrynnikov, Phys. Rev. A 53, 4611 (1996)] are standard in the theory of NMR. They were used by most authors and gave satisfactory results in comparison with experiments as is well documented in the literature. I explain why I feel that different assumptions will not give an essential quantitative improvement. © 1996 The American Physical Society.

Electric-dipole-moment experiments based on spin-precession measurements of stored atoms or neutrons are generally considered to be immune from the effects of v×E or motional magnetic fields. This is because the average velocity for such systems is zero. We show here that the fluctuating field associated with the random velocity, heretofore not considered, can in fact lead to sizable systematic effects.