Optical-optical double-resonance fluorescence excitation spectra of molecular Rydberg states of CaF are reported, and states up to 45 500 ${\mathrm{cm}}^{\mathrm{-}1}$ above the X ${}_{}{}^2{}_{}{}^{}\mathrm{\Sigma }_{}^{+}{}_{}{}^{}$ ground state are rotationally analyzed. The new electronic states are arranged into six ‘‘core-penetrating’’ Rydberg series by fitting their energies to the Rydberg equation using effective principal quantum numbers. The ionization potential of CaF is thereby determined to be 46 998±5 ${\mathrm{cm}}^{\mathrm{-}1}$. Spin-orbit, Λ-doubling, and spin-rotation constants are determined for a subset of the observed states. Scaling relationships for each of these fine-structure effects are developed and shown to yield characteristic scaling parameters for each series. Analysis, using ${\mathrm{Ca}}^{+}$ atomic orbitals as a basis set for the molecular Rydberg orbitals, shows that each of the six observed molecular Rydberg series correlates with a core-penetrating Rydberg series of the ${\mathrm{Ca}}^{+}$ ion, and that the p∼d mixing suggested by the spin-orbit scaling parameters of the ${}_{}{}^2{}_{}{}^{}\mathrm{\Pi }$ states is consistent with that previously determined for low-lying states using a ligand-field model. The spin-orbit scaling parameter for the lone ${}_{}{}^2{}_{}{}^{}\mathrm{\Delta }$ series is consistent with pure l=2 character. In the lowest-lying state of each series, n∼(n+1) mixing is shown to account for deviations of the molecular constants from scaling predictions based on the corresponding constants of the higher-lying states. The coefficients of scaling relations for the Λ-doubling and spin-rotation constants reveal interseries interactions which are consistent with substantial l mixing and which suggest that multistate perturbation and/or multichannel quantum-defect analyses should be pursued.

Precise line-shape measurements of the Q(0) to Q(4) lines in ${\mathrm{D}}_2$ have been made using Raman gain spectroscopy. At the densities studied (2.5–30 amagat), the Q-branch lines are well separated but slightly asymmetric due to quantum-mechanical line mixing. We have measured both the symmetric and the asymmetric contributions to the line shape as a function of the density. From the broadening coefficients and the line-mixing parameters, we have deduced the dephasing and the state-to-state rotational relaxation rates. Semiquantitatively, the results support the empirical modified-exponential-gap law.

Calculations of the rotational Raman spectra of hydrogen at high gas densities and various temperatures are presented. Both the far wings and the line cores are considered where collisional induction and pressure broadening shape the profiles. The treatment of far wings follows previous calculations which had given encouraging results. In the present work, new components of the collision-induced polarizability have been considered in an attempt to remove the previously observed inconsistencies with existing measurements. The far-wing spectral intensities and the Raman linewidths are computed by using two different intermolecular potentials. It is shown that Raman linewidths are more sensitive to the details of the intermolecular potential than far-wing Raman intensities. Comparison with experimental data does not allow one to determine which of the two potentials is to be preferred over the other.

We report observation of beats in the time-resolved spectra of ${}_{}{}^{125}{}_{}{}^{}\mathrm{Te}_2^{}{}_{}{}^{}$ superfluorescence. The results are used to determine hyperfine contributions in the B $0_{\mathrm{u}}^{+}$ state.

Valence photoelectron spectra of Zn and Hg have been recorded by using monochromatized synchrotron radiation in ultraviolet region and monochromatized Al Kα radiation (hν=1487 eV), respectively. In the region of the double-ionization thresholds, satellite states associated with the ${\mathit{nd}}^{\mathrm{-}1}$ single-hole states (n=3 for Zn and n=5 for Hg) are observed above the ${\mathit{nd}}^{10}$ ${}_{}{}^1{}_{}{}^{}$S double-ionization threshold. The Auger decay of these satellites may account significantly in the formation of the ${}_{}{}^1{}_{}{}^{}$S state of the dication. In case of Zn, the asymmetric profile of the main satellite lying above the 3${\mathit{d}}^{10}$ ${}_{}{}^1{}_{}{}^{}$S double-ionization threshold suggests the existence of a coupling between the discrete satellite state with this underlying shake-off continua.

We report on n=3 to n=3 soft-x-ray transitions from the highest nuclear charge (Z=82) Na-like ions yet obtained. The results are tied to accurate calculations including screened QED contributions and confirm theoretical trends observed by Kim et al. [Phys. Rev. A 44, 148 (1991)]. Weak Ne-like and Mg-like lines are observed in an accelerator-based experiment in the energy range near 800 eV and compared to multiconfiguration Dirac-Fock calculations.

Angular distributions of ${\mathit{L}}_3$ x-ray transitions, including electric-dipole-forbidden ones, were measured for 1-, 2-, and 3-MeV proton impact on a thorium target, where the excitation and detection systems were cylindrically symmetric. A sophisticated spectrum-analysis technique was applied, where both the Lorentzian broadening of the transitions and the Si(Li) detector response function with various tailing features were taken into account. The anisotropy-parameter ratios are expected to be independent of the ionization process, and to be characteristic of the x-ray transitions in the independent-particle model. The ratios of the anisotropy parameters of the electric-dipole-allowed transitions were in disagreement with this expectation, even when the higher-order multipole contributions were taken into account. These results follow the same trend as earlier angular distribution and angular correlation measurements. Additionally, the electric-dipole-forbidden ${\mathit{LtL}}_3$${\mathit{M}}_2$) and Ls(${\mathit{L}}_3$${\mathit{M}}_3$) transitions had a ${\mathit{P}}_4$(cos(θ)) term, which is not expected within the framework of the single-particle-model predictions. Possible causes for this discrepancy are explored.

We discuss the dynamics of a polar molecule simultaneously affected by a highly intensive microwave field and by the random perturbation due to collisions with the atoms of a buffer gas. The condition of quantum chaos is assumed to be satisfied for the molecule. It is shown that under the influence of the collisions the system relaxes into the specific steady-state regime which in some sense can be referred to as a ‘‘chaotic steady-state regime.’’ The theoretical study is supported by a numerical simulation using the system parameter values corresponding to a heavy diatomic molecule.

In the pseudopotential approximation the type of dynamics of two charged particles confined in a Paul trap depends on the ratio λ=${\mathrm{\omega }}_{\mathit{z}}$/${\mathrm{\omega }}_{\mathrm{\rho }}$ of the frequencies of the axial and the radial pseudo-oscillators, respectively. For λ=1/2,1,2 the classical dynamics is integrable. The classical dynamics appears to be nonintegrable for λ≠1/2,1,2 and shows a mixed phase space with interspersed regular and chaotic regions. The type of classical dynamics manifests itself in the statistics of the quasienergy spectrum of the Paul trap. In the integrable case (λ=1/2,2) we find level clustering, whereas level repulsion is obtained in the chaotic regime.

We examine the radiative properties of a two-level atom driven by a strong bichromatic field with frequencies ${\mathrm{\omega }}_1$=${\mathrm{\omega }}_0$-${\mathrm{\delta }}_1$ and ${\mathrm{\omega }}_2$=${\mathrm{\omega }}_0$+${\mathrm{\delta }}_2$, which can be asymmetrically placed about the atomic transition frequency ${\mathrm{\omega }}_0$ and can have different Rabi frequencies ${\mathrm{\Omega }}_1$ and ${\mathrm{\Omega }}_2$. Applying the optical Bloch equations for the bichromatic excitation, we derive an infinite set of equations of motion for the time evolution of the atomic variables. The equations are solved numerically by matrix inversion and Laplace transforms. Using the quantum regression theorem, we then solve for the steady-state total fluorescence intensity, and the resonance-fluorescence and absorption spectra. The spectra are found to depend on the frequency difference 2δ=${\mathrm{\delta }}_1$+${\mathrm{\delta }}_2$, the average detuning Δ=${\mathrm{\omega }}_0$-1/2(${\mathrm{\omega }}_1$+${\mathrm{\omega }}_2$), and the Rabi frequencies of the driving fields. For ${\mathrm{\Omega }}_1$=${\mathrm{\Omega }}_2$=Ω, the total fluorescent intensity displays a series of maxima for Δ=±nδ∓${\mathrm{\Omega }}^2$/4δ, where the n are the odd integers. The intensity-dependent shift from the resonances nδ is explained as an analog of the generalized Bloch-Siegert shift. The resonance-fluorescence spectrum for Δ≠0 appears to contain more peaks than that for Δ=0.

This is due to the splitting of the central peak and the even sidebands into doublets. The absorption spectrum of a weak-probe beam for Δ=0 and equal Rabi frequencies consists of a symmetric series of dispersionlike sidebands separated from ${\mathrm{\omega }}_0$ by integer multiples of δ, together with a central absorption peak at ${\mathrm{\omega }}_0$, whose amplitude oscillates with Ω. For Δ≠0 and/or ${\mathrm{\Omega }}_1$≠${\mathrm{\Omega }}_2$, the odd sidebands remain dispersionlike, while the central peak and the even sidebands split into absorption-emission doublets. A simple physical interpretation of the spectral features is given in terms of the dressed-atom model.

Parametrically pumped electron oscillators synchronize abruptly when the pump power exceeds a threshold and the oscillators are radiatively cooled in a cylindrical Penning trap. The collisionally coupled electron oscillators are under precise experimental control and exhibit a rich and varied nonlinear dynamics, with abrupt thresholds, hysteresis, abrupt transitions between bistable response phases, etc. Synchronized electrons are an ideal probe of the radiation field of a trap cavity, opening the way to a new generation of electron magnetic-moment measurements and to sideband cooling of an electron motion to millikelvin temperatures.

With the help of uniform semiclassical approximations the quantitative connection between classical bifurcation phenomena and the dynamics of an electronic Rydberg wave packet in the presence of an external static magnetic field is discussed with particular emphasis on nongeneric bifurcations of the Edmonds-Garton-Tomkins orbit.

We present a theoretical analysis of the influence of the collimation of a strong pump beam on a small-signal-gain line shape in a three-level Λ-type molecular system in the regime of high pump intensity when saturation and Stark (Autler-Townes) splitting of the levels of the pumping transition take place. The cases of homogeneous and Doppler-broadened pumping transitions have been considered. A significant offset, an asymmetric deformation, and a narrowing of the gain line, i.e., a spectrum focusing, have been obtained and explained as a result of the nonlinear (dispersion) and the active (gain) wave guiding of the small signal in the field of the strong pump beam.

In this paper, a general formalism for treating both steady-state and time-resolved second-harmonic generation for molecular systems is presented. Here, only the steady-state case will be reported. The adiabatic approximation is introduced. Four important cases, resonance-resonance, resonance–off-resonance, off-resonance–resonance, and off-resonance–off-resonance transitions, have been considered. Finally, numerical calculations of rhodamine 6G are performed to demonstrate the applications of theoretical results.

The noise-transformation properties of competing four-wave-mixing processes in an optical fiber are numerically investigated for an input signal with two frequency components, ${\mathrm{\omega }}_1$ and ${\mathrm{\omega }}_2$. When pulses from such a source propagate through a single-mode optical fiber, the two input frequency components can mix to form symmetric pairs of sidebands at ${\mathrm{\omega }}_3$=2${\mathrm{\omega }}_1$-${\mathrm{\omega }}_2$, ${\mathrm{\omega }}_4$=2${\mathrm{\omega }}_2$-${\mathrm{\omega }}_1$, ${\mathrm{\omega }}_5$=2${\mathrm{\omega }}_3$-${\mathrm{\omega }}_1$, and ${\mathrm{\omega }}_6$=2${\mathrm{\omega }}_4$-${\mathrm{\omega }}_2$. Noise that was initially confined to the input frequencies ${\mathrm{\omega }}_1$ and ${\mathrm{\omega }}_2$ is redistributed to the sidebands in a way that reduces the relative intensity fluctuations of the input frequencies, when the fiber length is judiciously chosen.

We have experimentally determined all of the quantities involved in the uncertainty relation for the phase and photon number of a mode of the electromagnetic field when the field mode is in a coherent state of small average photon number. This is accomplished by determining the quantum state of the field using optical homodyne tomography, which uses measured distributions of electric-field quadrature amplitude to determine the Wigner function and hence the density matrix. The measured state is then used to calculate the uncertainty product for the number and phase, as well as the expectation value of the commutator of the number and phase operators. The experimental results agree with the quantum-mechanical predictions. We also present measured phase- and photon-number distributions for these weak coherent states, as well as their measured complex wave functions.

Atomic homodyne detection allows the field characteristic function to be reconstructed from the excitation probabilities of probe atoms that interact both with the prepared cavity field and a reference driving field. We examine the effects of retaining a full quantum description of both fields and show that the homodyne approximation limits the time of observation of the field. This in turn limits our ability to reconstruct precisely the field characteristics from the restricted data, and can make it impossible to determine fine quantum detail, and, in particular, to discriminate between field superpositions and statistical mixtures.

We introduce a formal state of the radiation field which interpolates between the (pure) number (Fock) state and the (nonpure) chaotic state. The correlation functions and the squeezing properties are studied. The study of two quantum optical systems (namely, the Jaynes-Cummings model and resonance fluorescence for a single atom and many cooperative atoms) in such a state of the radiation field provides more insight into the gradual behavior as one goes from the number state to the chaotic state. A scheme for the production of such a state is sought to be realized in a model of multiphoton processes in a finite-level atomic system. The quasiprobability Wigner distribution function for such a state is also examined.

We derive the quantum limits for an atomic interferometer from a second-quantized theory in which the atoms obey either Bose-Einstein or Fermi-Dirac statistics. It is found that the limiting quantum noise is due to the uncertainty associated with the particle sorting between the two branches of the interferometer, and that this noise can be reduced in a sufficiently dense atomic beam by using fermions as opposed to bosons. As an example, the quantum-limited sensitivity of a generic matter-wave gyroscope is calculated and compared with that of a laser gyroscope.

A micromaser containing a Kerr medium in its cavity has been investigated. We have presented an exact solution to the model Hamiltonian, which, apart from the usual Jaynes-Cummings terms, contains a Kerr term (${\mathit{a}}^{\mathrm{°}2}$${\mathit{a}}^2$). We have shown that the Kerr cavity nonlinearity significantly modifies the photon statistics of the micromaser field. Particularly, it is interesting to note that with the introduction of appropriate nonlinearity a micromaser can be made to approach towards a number state with a low number of photons.