Atomic coherence, when combined with a reduction of pump noise, can lead to significant noise quenching in lasers and even squeezing in masers. Furthermore, this noise reduction can be modified in an interesting way by atomic broadening.

By means of the technique of determinant calculation, an explicit N-soliton solution of the modified nonlinear Schrödinger equation is obtained for arbitrary N using the method of a meromorphic transformation matrix. The final expression is written in a form suitable for practical needs. Its expected asymptotic behavior is derived.

We report an observation of atoms stopped by laser light in an experiment using the Zeeman tuning technique. In contrast to previous experiments using the same technique, we are able to stop the atoms outside the slower solenoid using a single laser. The deceleration process is monitored through the measurement of the fluorescence along the deceleration path in such a way that the slower laser is also used for diagnosis. This technique also permits the realization of a few interesting observations on the process such as the position where the atoms stop scattering photons.

It is shown that in accordance with the results of Ning Lu [Phys. Rev. A 40, 1707 (1989)] the photon number state and the squeezed vacuum state are much more vulnerable to small loss than the coherent state. Furthermore, unlike the coherent state, they do not recover when the loss is compensated by a subsequent amplification. It is also shown that the Wigner function retains essential information about the original photon number of a decaying number state up to a loss of 1/2 of the original energy.

A model of a hybrid optical system, originally set out in the form of a high-order delay-differential equation with a single discrete delay, is expressed in terms of an equivalent first-order equation with a γ-distributed delay. This makes clear why results converge for two limiting versions of the original equation, one of first order with discrete delay, the other of very high order without delay.

We have defined a new nonclassical effect: amplitude kth-power squeezing. We have analyzed the squeezing properties of the k-photon coherent states as defined by D’Ariano, Rasetti, and Vadacchio [Phys. Rev. D 32, 1034 (1985)]; Katriel et al. [Phys. Rev. D 34, 332 (1986)]; and D’Ariano and Sterpi [Phys. Rev. A 39, 1810 (1989)]. It has been shown that, due to the interaction with the nonlinear nonabsorbing medium modeled as an anharmonic oscillator, these states become amplitude kth power squeezed.

We present some effects of a squeezed vacuum on the photon statistics of a coherently driven two-level atom. The intensity-intensity correlation function ${\mathit{g}}^{\mathrm{}\left(2\right)\mathrm{}}$(τ), Mandel’s response function Q(T), and the photon-counting distribution P(0,T) show the manifestation of the inhibition of atomic phase decay in the presence of a squeezed vacuum.

Emission and absorption from two two-level atoms interacting with a single mode of a cavity field in the vacuum state are investigated. The role of cavity losses, detuning, and cooperativity on the Rabi oscillations is studied. Absorption from a weak probe field with the cavity at zero temperature computed to third order in the atom-probe coupling constant is analyzed to determine the effect of cavity damping and detuning on the Rabi splitting.

In the recent article by M. Bylicki [Phys. Rev. A 39, 3316 (1989)], many remarks were made concerning the saddle-point technique developed by this author. These remarks appear to have been based on a misunderstanding of both the spirit as well as the actual application of this method. In this Comment, I shall try to clarify some of these misunderstandings, and one hopes, put the problem in its proper perspective.

It is argued that the saddle-point method developed by Chung [Phys. Rev. A 20, 1743 (1979)] may be considered in the category of orthogonalization to the open-channel space, and that the generalization of the method introduced by Bylicki offers a precise prescription for implementation of the original formulation by Chung.

We show that the approach of Trombetta, Basile, and Ferrante [Phys. Rev. A 40, 2774 (1989)] does not establish the Keldysh ansatz as a well-defined approximation. In particular, it in effect replaces a vanishing contribution to the ionization rate by a nonvanishing one.

We reply to the preceding Comment by Antunes Neto, Davidovich, and Milonni [Phys. Rev. A 41, 4095 (1990)] on our paper dealing with the Keldysh approximation for multiphoton ionization of atoms [Phys. Rev. A 40, 2774 (1989)]. We show by a concrete example how the replacement of the free evolution operator by the atomic one, leading to the Keldysh transition amplitude, can be justified for weak- and short-range binding potentials.

From a laser spectroscopic study of isotope shifts in the 1s2s ${}_{}{}^1{}_{}{}^{}$S${,}^3$S→1snp transitions in ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ and of the hyperfine structure in the 1snp Rydberg states of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ we have derived highly accurate information on mass-polarization effects in the 1s2s ${}_{}{}^1{}_{}{}^{}$S and ${}_{}{}^3{}_{}{}^{}$S states. The experimental results, which are in good agreement with recent, high-precision variational calculations, confirm an isotope dependence of 〈${\mathbf{p}}_1$⋅${\mathbf{p}}_2$〉. .AE

The resonant transfer and excitation cross sections in collisions of ${\mathrm{U}}^{89+}$ ion with light targets have been calculated in impulse approximation using the multiconfiguration Dirac-Fock method. Effects of relativity not only shift the peak positions significantly but also change the number of peaks. Relativistic effects have been found to increase the total dielectronic recombination strength by 50%. Including Breit interaction in calculations of Auger matrix elements can enhance the resonant transfer and excitation cross sections by as much as a factor of 2.

A source of hyperthermal, ground-state, impurity-free, atomic oxygen of an energy variable in the range 2–100 eV has been developed. Experimental results are presented of emission spectra in the wavelength range 250–850 nm produced by collisions of 5-eV O${(}^3$P) atoms with adsorbed NO and CO molecules on a ${\mathrm{MgF}}_2$ surface. The emission with adsorbed CO is due to the B̃→X̃ transition in ${\mathrm{CO}}_2$, while that with NO is consistent with the continuum B̃→X̃ and Ã→X̃ emissions in ${\mathrm{NO}}_2$.

We report a measurement of the lifetime of the $2^3$${\mathit{S}}_1$ level in heliumlike ${}_{}{}^{79}{}_{}{}^{}\mathrm{Br}_{}^{33+}{}_{}{}^{}$. Our result is ${\mathrm{\tau }}^{\exp }$(2 ${}_{}{}^3{}_{}{}^{}$${\mathit{S}}_1$)=224.1(7.1) ps. This agrees with the theoretical calculation of 230(2) ps and provides a test of O(${\mathit{Z}}^2$${\mathrm{\alpha }}^2$) corrections to the lifetime. The experimental error is dominated by uncertainties in the correction required to account for long-lived cascades from highly excited states.

Production of higher harmonics in a model atom described by a three-dimensional δ-function potential in the presence of a monochromatic linearly polarized field is investigated. The rates for production of the individual harmonics can be expressed as one-dimensional integrals. The only property of the atom that enters the model is its ionization energy. The results are in qualitative agreement with many of the data. In particular, the model exhibits a ‘‘rising plateau.’’

By a judicious choice of operating conditions, we have succeeded in achieving a very high gain operation of a cw ${\mathrm{CO}}_2$ laser. It is found that for gain above threshold values of more than 5.2, the emission of the laser breaks down, giving rise to oscillations in space as well as low-frequency oscillations in time (1.6 kHz, while the free spectral range of the laser cavity is 50 MHz). The spatial and temporal instabilities that coexisted were found to have a critical dependence on the gain above threshold values.