A response is made to the three assertions of Škrinjar, Kapov,and Stojanović [Phys. Rev. A 37, 639 (1988)].

Based on path-integral formalism we derive expressions for nonorthogonal matrix elements. The result reduces to few integrals in a multivalued complex plane. The present approach represents an improvement over earlier work in that the matrix elements are much more accurate.

Inclusion of the Coulomb phase in the calculation of the scattering amplitude is important. Previous calculations of the resonance fluorescence polarization of the Be II $2p-2s$ decay after electron excitation omitted the phase and are shown to be incorrect. Differential cross sections for the Mg II $3s\to 3p$ transition are also presented, which also exhibit peculiar effects caused by the Coulomb phase.

A hypothetical discussion on the turbulence in a cold gas interacting by the gravitational force is presented. We evaluate the density-density correlation function as $\xi \mathrm{}\left(r\right)=C\left(t\right)\mathrm{}{r}^{-2\mathrm{}}$ with a time-dependent coefficient $C\left(t\right)\mathrm{}$.

We study the interfacial modes of a driven diffusive model under suitable nonequilibrium conditions leading to possible instability. The external field parallel to the interface, which sets up a steady-state parallel flux, enhances the growth or decay rates of the interfacial modes. More dramatically, asymmetry in the model can introduce an oscillatory component into the interfacial dispersion relation. In certain circumstances, the applied field behaves as a singular perturbation.

We measured the distribution of conformational barriers in a chromoprotein by using a spectral hole as a probe. The results can be interpreted by a superposition of glasslike states and a discrete feature with a Gaussian distribution.

Potassium vapor, contained together with a buffer gas in a fluorescence cell located in a 7-T magnetic field, was irradiated with light from a pulsed dye laser producing selective excitation of the $5^2$$P_{1/2}$,-1/2 or the $5^2$$P_{3/2}$,-3/2 Zeeman substate. Collisions of the excited and polarized atoms and the resulting Zeeman mixing produced a population of the whole Zeeman manifold and resulted in the emission of a fluorescent Zeeman spectrum which was resolved with a Fabry-Perot interferometer and registered with a photomultiplier and multichannel scaler. Measurements of the relative intensities of the fluorescence components yielded the absolute (thermally averaged) multipole-relaxation cross sections and cross sections for Zeeman mixing by collisions with He, Ne, and Ar atoms.

A pulsed helium-discharge plasma was found to have two peaks in the temporal development of its emission line intensities. At these peaks the population densities of the n ${\mathrm{}}^3$D state (n=3,4,. . .) were measured. For the first peak, the populations were found to be proportional to $n^{\mathrm{-}6}$, while the second peak showed an exp[-E(n)/${\mathrm{kT}}_e$] dependence. These distributions are identified with plasma in its ionizing and recombining phases, respectively. On the basis of a collisional-radiative model calculation, the transition from the ionizing phase to the recombining phase is demonstrated. This report is the first experimental demonstration of the $n^{\mathrm{-}6}$ distribution in the ionizing phase for conditions when the conventional criterion would indicate thermal populations. It is suggested that the apparent decrease in the emission line intensities of high-n members of series lines, or ‘‘the transparency window’’ that is observed in dense plasmas, may be attributed to this characteristic of ionizing plasma.

The laser-induced-fluorescence spectroscopy has been applied to an afterglow plasma (2 torr of 5% neon and 95% helium mixture gas), and we have observed disalignment of the neon 2$p_2$-level atoms under the condition of $n_e$=5.1×${10}^{19}$ ${\mathrm{m}}^{\mathrm{-}3}$ and $T_e$=2.0×${10}^3$ K. The disalignment rate due to atom collisions has been determined separately. The effect of ion collisions is considered in the approximation of the static ion microfield—the Holtsmark field. This field affects and decreases the initial alignment, and its effective rate is estimated. The disalignment rate coefficient due to electron collisions is deduced to be (4.1±1.0)×${10}^{\mathrm{-}13}$ ${\mathrm{m}}^3$ ${\mathrm{s}}^{\mathrm{-}1}$. This rate coefficient is found to be consistent with the Stark broadening due to electron collisions.

We have performed a vibrationally resolved two-state coupled-channel calculation using the Padé-approximant C̃-functional formalism for the ν’=0←ν’’=0, ν’=1←ν’’=0, and ν’=2←ν’’=0 vibrational transitions in the photoionization of ${\mathrm{N}}_2$ leading to the (3${\sigma }_g$${)}^{\mathrm{-}1}$$X^2$${\Sigma }_g^{+}$ and (2${\sigma }_u$${)}^{\mathrm{-}1}$$B^2$${\Sigma }_u^{+}$ states of ${\mathrm{N}}_2$${\mathrm{}}^{+}$. We have found that both the vibrationally resolved ν’=0←ν’’=0 and the vibrationally averaged asymmetry parameters in the (2${\sigma }_u$${)}^{\mathrm{-}1}$ channel are in good agreement with vibrationally unresolved experimental data. However, the theoretical results presented here do not resolve the apparent discrepancies between the vibrationally resolved and vibrationally unresolved experimental data. Coupled-channel photoelectron asymmetry parameters and photoionization cross sections in the (3${\sigma }_g$${)}^{\mathrm{-}1}$ channel were not found to be substantially different from earlier single-channel results. The results presented here demonstrate the need for the inclusion of further electronic correlation effects in order to give a more quantitatively accurate description of the photoionization of ${\mathrm{N}}_2$.

The Kramers-Henneberger transformation is used to treat potential scattering of electrons in the presence of a strong laser field. As a first step, the one-dimensional scattering by a polarization potential is considered. It is shown that the static part of the effective potential, often called the dressed potential, may support more bound states than the original potential depending on the intensity and frequency of the field. Exact results for the transmission and reflection coefficients are presented and two approximations are discussed: A perturbative approach based on the above transformation and the adiabatic approximation.

Properties that depend on the anisotropy of the electron momentum distribution of ${\mathrm{N}}_2$(X ${\mathrm{}}^1$${\mathrm{\Sigma }}_{\mathrm{g}}^{+}$) have not been determined accurately even by a fairly sophisticated calculation [Phys. Rev. A 34, 4695 (1986)] using a configuration-interaction wave function. This paper reports calculations based on a series of wave functions designed to assess the sensitivity of one-electron momentum-space properties of ${\mathrm{N}}_2$ to variations in the treatment of electron correlation and the choice of basis sets of Slater-type functions. The most elaborate of these wave functions, which consists of 169 650 configurations, provides satisfactorily converged predictions of a wide variety of isotropic momentum-space properties as well as directional Compton profiles. However, the anisotropy of the kinetic energy tensor turns out to be so small in magnitude that even its sign remains uncertain.

The origins of the electromagnetic field of the Kerr-Newman source are a system of currents and of electric surface charges which are distributed over a circular disc of radius a, centered at the origin, and oriented normally to the direction of the angular momentum vector. For a positive total electric charge e, the surface-charge density is negative inside the disc, becoming infinitely negative as the rim of the disc is approached. On the rim, there is a positive charge of infinite density which not only neutralizes the negative charge distributed in the interior of the disc, but also leaves a residue of a positive charge equal to e. Similarly, the currents flow in the negative direction inside the disc, with a current density which becomes infinitely negative at the rim. On the rim there is a positive current of infinite intensity, which generates a magnetic moment compensating the negative magnetic moments distributed in the interior, and leaves a net integrated magnetic moment of magnitude ea, the latter being equal to the dipole component of the total magnetic moment. The gyromagnetic ratio for the total magnetic moment is 2, as it is for the dipole component.

The integral transform (generator coordinate) method has been applied to calculate the binding energies and some expectation values for the positronium negative ion and for the recently discovered muonium negative ion. For both ions the wave functions obtained are compact and accurate.

Measurements are presented representing a complete set of electron-photon polarization correlation parameters for the excitation of n ${}_{}{}^1{}_{}{}^{}P$ states of He at an incident energy of 80 eV and an electron scattering angle of 20°. The data support the predictions of a recent theoretical paper that these parameters should exhibit little variation with n. However, disagreement in absolute values between experiment and theory indicates the need for additional theoretical input into the problem.

An improved anisotropy measurement of the Lamb shift is obtained by means of a new method for the high-precision measurement of light intensities. The photon-counting techniques used in our previous work [Phys. Rev. A 20, 1299 (1979)] are replaced by the direct measurement of photoelectron currents with high-precision electrometers. Our new value for the Lamb shift in ${\mathrm{He}}^{+}$ is 14 041.9±1.5 MHz. This agrees with the earlier microwave resonance measurement of Lipworth and Novick [Phys. Rev. 108, 1434 (1957)], but lies clearly below the more recent measurement by Narasimham and Strombotne [Phys. Rev. A 4, 14 (1971)].

Absolute differential cross sections of electrons vibrationally elastically scattered from water vapor have been measured at room temperature by electron impact. A modulated crossed-beam method was used. The energy and angular range covered were from 2.2 to 20 eV and from 15° to 150°, respectively. Strong backward scattering has been observed as predicted by theory. The measured integrated and momentum-transfer cross sections are generally larger than others in the literature by 50%.

The partial photoionization cross sections of the 5s, 4p, and 4s subshells of atomic strontium are calculated with the use of many-body perturbation theory. Resonance structure due to single excitations of the 4p and 4s electrons is studied in detail. The effect of spin-orbit splitting is included for some of the low-lying 4p→nd,ns resonances. The β asymmetry parameter is calculated for the 4p excitations. Comparison is made with other theory and experiment at the 5s threshold and for the spin-orbit splitting.

Moments, S(j,K), of the generalized oscillator strength distribution are global properties of the Bethe surface. Apart from S(-1,K) which is related to the Waller-Hartree incoherent scattering factor, little is known about these moments for nonzero K. This paper describes high-accuracy calculations of S(1,K) and S(2,K) for molecular hydrogen. Comparison with experiment is made, and the utility of simple asymptotic approximations is confirmed. The moments are used to calculate differential cross sections for the inelastic scattering of x rays using the constant-momentum-transfer and constant-angle theories of Bonham. These cross sections differ from the Waller-Hartree cross sections at large angles thus demonstrating the importance of making corrections to the Waller-Hartree theory if the incoherent scattering factor S(K) is to be extracted from experimental inelastic cross sections. Total cross sections for scattering of 6- and 7-keV photons from ${\mathrm{H}}_2$ are compared with synchrotron radiation scattering experiments. The calculations suggest that the Bonham constant-angle cross sections agree best with experiment. However, further experimental and theoretical work is needed to obtain firm conclusions about the limitations of Waller-Hartree theory.