This work explores the dissociation dynamics and angular distribution of the HF molecule interacting with intense half-cycle and few-cycle pulses, including the rotational degree of freedom. The dependences of the dissociation probability on both the pulse type and the pulse duration are discussed. Our results indicate that the angular distribution of the dissociation probability is highly asymmetric to the perpendicular direction of field polarization, and becomes more symmetric with an increase in the number of field cycles. The spatial distribution of the wave function demonstrates the feasibility of constructing a molecular wave packet by interacting with the half-cycle pulse.

A method is proposed to produce population inversion on transitions involving the ground state of atoms. The method is realized experimentally with sodium atoms. Lasing at the frequency corresponding to the sodium $D_2$ line is achieved in the presence of pump radiation resonant to the $D_1$ line with helium as a buffer gas.

The interaction of an alkali-metal atom with two different color laser beams is analyzed. The quantum interference effect is studied in weak and strong field limits. Our theoretical results are related to the recent experimental data for the $S_{1/2}\to S_{1/2}$ two-photon transition in Na and Rb atoms. It is shown that the interference profile becomes narrow for moderately strong fields and the destruction of the interference is predicted for very strong ones. The electromagnetically induced interference effects are analyzed. The role of the relaxation processes is examined.

Highly accurate Born-Oppenheimer potential-energy surfaces of ${\mathrm{H}}_3$ were calculated and combined with multichannel quantum-defect theory (MQDT) to predict with high precision the photoionization cross section of laser-excited triatomic hydrogen recently measured in this laboratory. The experiment first prepares ${\mathrm{H}}_3$ in stepwise excitation in a single rotational level of the symmetric stretch excited $3s$ Rydberg state. One-photon ionization from this state populates the continuum and $\mathrm{np}$ Rydberg states which autoionize into ${\mathrm{H}}_3^{+}{+e}^{-}.$ In the vicinity of the first symmetric stretch excited level of ${\mathrm{H}}_3^{+}$ the ionization spectrum shows features similar to those observed at the lowest ionization threshold: a quasidiscrete region below the first symmetric-stretch excited threshold, a Beutler-Fano region of rotational autoionization and interlopers of low-$n$ Rydberg states belonging to high vibrationally excited cores dispersed over the continuum. The MQDT calculations include rotational, vibrational, and Jahn-Teller interactions, and permit the assignment of most of the spectral features.

Laser-cooled atoms from a low-velocity atomic source are guided in a hollow-core optical fiber using the evanescent-wave dipole force from blue-detuned laser light launched into the glass region of the fiber. The transverse velocity of the guided atoms corresponds to a temperature of $50\hspace{0.5em}\mu \mathrm{K}.$ We achieve a maximum flux through a 23.5-cm-long fiber of 590 000 atoms/second with a laser power of 55 mWatts at a detuning of 6 GHz. With larger detunings of 40 GHz, spontaneous emission from the atoms inside the fiber can be suppressed and the atom’s internal-state population is preserved. We identify two major loss mechanisms for the guiding process and discuss possible solutions.

We present a simulation of the laser absorption spectra of Eu atoms in the $a{}^8{S}_{7/2}-y{}^8{P}_{7/2}$ band at $462.7\hspace{0.5em}\mathrm{nm}$ measured previously in a buffer-gas-loaded magnetic trap [J. Kim et al., Phys. Rev. Lett. 78, 3665 (1997)]. The simulations of the hyperfine-resolved Zeeman spectra are based on exact magnetic eigenproperties of the states involved, and yield a complete assignment of all the features observed. This reveals that apart from the $M_J=7/2\mathrm{}$ state and its hyperfine substates, the $M_J=5/2\mathrm{}$ and $3/2$ states are also trapped at $B_{\max }=0.52\mathrm{}\hspace{0.5em}\mathrm{T}$ and a temperature of about $250\hspace{0.5em}\mathrm{mK}.$

High-precision ion yields are taken with 30-fs ultrashort laser pulses in various species of doubly ionized diatomic molecules, ${\mathrm{N}}_2$ and ${\mathrm{O}}_2,$ including metastable, charge symmetric, and asymmetric dissociating channels. The experimental results indicate that the detailed electronic structure is a critical factor influencing strong field nonsequential ionization. The study of ellipticity effects of nonseqential ionization is also extended, for the first time to our knowledge, to the molecular system.

The relative diffraction peak intensities of He atoms with an incident beam energy of 65 meV diffracted from a microfabricated 100 nm-period transmission grating are analyzed using both Fresnel and Fraunhofer diffraction theory. The projected slit width could be varied from 50 nm down to less than 1 nm by inclining the grating at angles up to ${\Theta }_0=42\mathrm{}°$ with respect to the incident beam. Good agreement between calculated and measured peak intensities, up to the sixth order, is obtained by accounting for random deviations in the slit positions, and averaging over the velocity spread of the incident beam as well as the spatial extent of the nozzle beam source. It is demonstrated that He atom beam diffraction together with simple transmission measurements is an excellent means of characterizing such gratings including a detailed determination of the slit width, the bar shape, and random as well as periodic disorder.

We study the mutual interaction of a Bose-Einstein condensed gas with a single mode of a high-finesse optical cavity. We show how the cavity transmission reflects condensate properties, and calculate the self-consistent intracavity light field and condensate evolution. Solving the coupled condensate-cavity equations we find that while falling through the cavity, the condensate is adiabatically transfered into the ground state of the periodic optical potential. This allows time-dependent nondestructive measurements on Bose-Einstein condensates, with intriguing prospects for subsequent controlled manipulation.

We propose a scheme to create high-contrast, periodic atom density distributions having period $\lambda /2n$ using the Talbot effect, where $\lambda$ is the wavelength of the optical fields that scatter the atoms and n is a positive integer. This filtered Talbot lens is comprised of two standing-wave optical fields. An atomic beam propagates perpendicular to the fields. The first field, which is far detuned from the atomic transition frequency, acts as an array of lenses that focuses the atoms. The second field, positioned at the atom optical focus of the first, is resonant with the atomic transition frequency and acts as an amplitude mask, leaving unperturbed only those atoms that pass through its nodes. At distances following the interaction with the second field that are equal to an integral fraction of the Talbot length, atomic density gratings having period $\lambda /2n$ are formed.

We calculate the two-photon $1S-2S$ spectrum of an atomic hydrogen Bose-Einstein condensate in the regime where the cold collision frequency shift dominates the line shape. Wentzel-Kramers-Brillouin and static phase approximations are made to find the intensities for transitions from the condensate to motional eigenstates for $2S$ atoms. The excited-state wave functions are found using a mean field potential, which includes the effects of collisions with condensate atoms. Results agree well with experimental data. This formalism can be used to find condensate spectra for a wide range of excitation schemes.

Quantum fluctuations in the radiation of multitransverse-mode laser are investigated theoretically and numerically, based on quantum c-number Langevin stochastic equations for the complex amplitudes of transverse modes. It is shown that strong antiphase quantum fluctuations of transverse-mode amplitudes occur, which corresponds to spatial fluctuations of the laser field. Fluctuation spectra are calculated, showing that antiphase fluctuations dominate at low frequencies (smaller than relaxation oscillation frequency), and in-phase oscillations prevail at high frequencies.

Using the coupled-system approach we calculate the optical spectra of the fluorescence and transmitted fields of a two-level atom driven by a squeezed vacuum of bandwidths smaller than the natural atomic linewidth. We find that in this regime of squeezing bandwidths the spectra exhibit unique features, such as a hole burning and a three-peak structure, which do not appear for a broadband excitation. We show that the features are unique to the quantum nature of the driving squeezed vacuum field and do not appear when the atom is driven by a classically squeezed field. We find that a quantum squeezed-vacuum field produces squeezing in the emitted fluorescence field which appears only in the squeezing spectrum while there is no squeezing in the total field. We also discuss a nonresonant excitation and find that depending on the squeezing bandwidth there is a peak or a hole in the spectrum at a frequency corresponding to a three-wave-mixing process. The hole appears only for a broadband excitation and results from the strong correlations between squeezed-vacuum photons.

We describe the quantum-noise behavior of a laser that has nonorthogonal polarization modes. The nonorthogonality of the modes leads to excess quantum noise. Theoretically, we derive the excess noise dynamics of the laser, including the saturation of the gain medium. Experimentally, we have measured the noise dynamics in the polarization, intensity and phase degrees of freedom of a 3.51-$\mu \mathrm{m}\mathrm{}$ HeXe laser and we obtain good agreement with theory. When the modes are made nonorthogonal we observe: (i) excess intensity and phase noise, (ii) spectral coloring of the excess intensity noise and (iii) correlations between the polarization-angle noise and the intensity noise. The excess phase noise is found to be partly suppressed by the polarization-anisotropic part of the saturation of the gain medium.

We study the dynamics of a laser oscillating on L optical transitions connecting a common upper level and L lower sublevels. Each transition is single mode. The minimal generalization of the rate equations to explain the experimental observations includes the low-frequency coherence dynamics [Europhys. Lett. 45, 307 (1999)]. These equations are studied analytically. We prove that such a laser has a low intensity self-pulsing threshold corresponding to the destabilization of the lowest of the relaxation oscillation frequencies. It also displays antiphased dynamics in the time-periodic regime, resulting in a vanishingly small oscillation amplitude of the total intensity while modal intensities have finite amplitude oscillations. The physical origin of this behavior is found to be the enhancement of stimulated absorption by quantum interference.

Theories unifying gravity and other interactions suggest the possibility of spatial and temporal variations of physical “constants.” Accuracy achieved for atomic optical frequency standards (optical clocks) approaches the level when possible time evolution of the fine-structure constant $\alpha$ can be studied by comparisons of rates between clocks based on different atomic transitions in different atoms. The sensitivity to variation of $\alpha$ is due to relativistic corrections that are different in different atoms $\left(\sim Z^2{\alpha }^2\right).\mathrm{}$ We have calculated the values of the relativistic energy shifts in In II, Tl II, Ba II, and Ra II, which all can be used as atomic optical clocks. The results are to be used to translate any change in the clock’s rate into variation of $\alpha .$

The momentum distributions of a homogeneous electron gas, arising from a simple one-matrix functional for the electron-electron repulsion energy that generalizes the Hartree-Fock and Goedecker-Umrigar approximations, are analyzed in detail. Their properties are found to depend strongly on the exponent β that enters the functional. Smooth momentum distributions that, together with the corresponding energies per particle, exhibit simple scaling behavior with respect to the electron density ρ, are obtained only for $\frac{4}{5}<\beta <\frac{4}{3}$ and $\rho <~{\rho }_{\mathrm{crit}}\left(\beta \right).\mathrm{}$

A realization is provided for the scattering states of the N-particle Calogero-Moser Hamiltonian. They are explicitly shown to be the coherent states of the singular oscillators of the Calogero-Sutherland model. Our algebraic treatment is straightforwardly extendable to a large number of few- and many-body interacting systems in one and higher dimensions.

A constructive procedure for generating a prescribed unitary transform via the optically driven evolution of a multilevel atom is described. Assuming a clean separation of the coupled levels, the procedure employs the rotating wave approximation together with a decomposition of a unitary matrix into simpler matrix factors with specified structure. Applications to state preparation and observation are also provided.

Gaussian Klauder coherent states are constructed for the harmonic oscillator, the planar rotor, and the particle in a box. The standard harmonic oscillator coherent states are given by expansions in the eigenstates of the Hamiltonian in terms of a complex parameter α. When the complex modulus of α is large, these states are identical in behavior with a particular choice of Gaussian Klauder coherent state. When the angular momentum of a planar rotor is large compared with Planck’s constant, the angle distribution associated with a Gaussian Klauder coherent state for this case remains sharply localized for many rotations. Similarly, for the particle in a box, it is possible to choose parameters in the Gaussian Klauder coherent state so that a localized particle bounces back and forth at constant velocity between the walls of the box for many periods without significant delocalization. Buried in this behavior is the Fourier series for a triangle wave. These examples show how Gaussian Klauder coherent states are of utility in understanding quantum-classical correspondence.