Yehuda Band - Academia.edu (original) (raw)
Papers by Yehuda Band
Physical Review A, 2007
Inelastic collisions of ultracold atoms or molecules are analyzed using very general arguments. I... more Inelastic collisions of ultracold atoms or molecules are analyzed using very general arguments. In free space, the deactivation rate can be enhanced or suppressed together with the scattering length of the corresponding elastic collision via a Feshbach resonance, and by interference of deactivation of the closed and open channels. In reduced dimensional geometries, the deactivation rate decreases with decreasing collision energy and does not increase with resonant elastic scattering length. This has broad implications; e.g., stabilization of molecules in a strongly confining two-dimensional optical lattice, since collisional decay of excited states due to inelastic collisions is suppressed. The relation of our results to the Lieb-Liniger model for bosonic atoms is addressed.
Optics Communications, 2004
Recent experimental developments in material sciences have generated hope that it will be possibl... more Recent experimental developments in material sciences have generated hope that it will be possible to devise optical media where the difference in group velocity between the fundamental and third harmonic may be strongly suppressed. Under these circumstances both pulses would travel together over a long distance. This would lead to an enhancement of the generation process, and hence strong focusing and/or using ultra-short pulses might not be crucial. If the perfect phase matching condition is assumed, the only remaining mechanisms to decrease efficiency are self and cross phase modulation. Here we suggest that, instead of exactly matching wave vectors, we admit a small mismatch and show how it can be tailored to compensate for the cross phase modulation of the third harmonic by the fundamental during the generation process. This is very beneficial for the efficiency of third harmonic generation, even increasing it by a factor of two or more.
Physical Review E, 2005
We find two-component optical solitons in a nonlinear waveguide with a Bragg grating, including K... more We find two-component optical solitons in a nonlinear waveguide with a Bragg grating, including Kerr effects and third-harmonic generation ͑THG͒. The model may be realized in temporal and in spatial domains. Two species of fundamental gap solitons ͑GSs͒ are found. The first ͑"THG-gap soliton"͒ has the bulk of its energy at the fundamental frequency ͑FF͒ and a lesser part in the third-harmonic ͑TH͒ band. The FF part of the soliton is always single humped; the TH part may be single or double humped. Stability domains for quiescent and moving THG-gap solitons strongly shrink with increase of velocity. The second species is the usual ͑"simple"͒ GS, sitting entirely in the TH band. More complex solutions are also found, in the form of a bound state of a THG-gap soliton and two simple GSs, with a finite binding energy. When a THG-gap soliton is unstable, the instability is oscillatory. It may ultimately cause the THG-gap soliton to throw off some radiation and evolve into a localized structure with the FF and TH components out of phase, with or without internal oscillations. Stable solitons feature an excited state ͑i.e., they support a localized eigenmode͒.
Advanced Solid State Lasers, 1991
We shall describe the spectrum, temporal dependence, and efficiency of intracavity second harmoni... more We shall describe the spectrum, temporal dependence, and efficiency of intracavity second harmonic generation ring lasers (ISHRL). We solve for the dynamics of ISHRL containing a homogeneously broadened gain medium, a phasematched doubling medium, a tuner, and a dichroic output coupler (see Fig. 1). The dynamics of each of these elements is described analytically (except for the doubling element, which must be solved numerically if the slowly varying envelope of the electric field is complex, i.e., if FM modulation is present). We show that cw single-mode operation of ISHRL is stable against the growth of additional modes due to amplitude-modulated (AM) fluctuations of the fundamental, however, frequency-modulated (FM) fluctuations are not damped. Cw operation tends to single longitudinal mode output provided no frequency modulation arises. Multimode frequency-modulated cw operation can be achieved. Methods for achieving anti-modelocked laser output are described. We consider the temporal dependence and efficiency of Q-switched ISHRL. Comparision with the Q-switched fundamental laser (not containing second harmonic generation) demonstrates that ISHRL can be even more efficient than the fundamental laser. General principies for assuring controlled intracavity fundamental intensity buildup are presented. Injection of multimode pulses and modelocked pulses into Q-switched ISHRL are considered.
Ultrafast Phenomena IV, 1984
In the passive mode-locking of a laser, the leading edge of the mode-locked pulse is shaped by th... more In the passive mode-locking of a laser, the leading edge of the mode-locked pulse is shaped by the rapid reduction of loss due to absorption saturation of the absorbing material. There are two mechanisms in general use for shaping the trailing edge of a mode-locked pulse. For gain media which saturate easily, such as organic dyes, the saturation of the gain which follows the peak of the pulse shapes the lagging edge of the pulse [1]. For gain media which cannot be saturated by an individual mode-locked pulse, because the saturation energy is too high, the trailing edge of the pulse continues to see gain and is not suppressed. For solid-state lasers (e.g., alexandrite, ruby, Nd:YAG, and Nd:Glass, etc.) which have high saturation energy, a saturable absorber with a fast relaxation time is used since a pulse with energy greater than the absorber’s saturation energy will experience the least loss in propagating through the cavity when the pulse length is shorter than the absorber’s relaxation time [2]. Therefore, by this mechanism the pulsewidths of broadly tunable, solid-state mode-locked lasers are limited by the relaxation times of saturable absorbers rather than the lasing bandwidth of the media.
Advanced Solid State Lasers, 1989
Second harmonic conversion (SHG) of Alexandrite is an effective means of obtaining tunable high p... more Second harmonic conversion (SHG) of Alexandrite is an effective means of obtaining tunable high peak power over the wavelength range 350-400nm. However, external SHG requires high intensity for efficient conversion and optical damage problems can result. An alternative is to utilize high intracavity intensities for conversion while at the same time use the SHG process as a power limiter for the intracavity fundamental laser beam. Intracavity SHG in a unidirectional Alexandrite ring laser with the only output at the second harmonic frequency was studied. Experimental results and their comparison with modeling studies of such a process will be discussed.
Coherence and Quantum Optics VI, 1990
Physical Review A, 1989
We present a method for e%ciently calculating the one-particle Green's function (OPCxF) for the i... more We present a method for e%ciently calculating the one-particle Green's function (OPCxF) for the interaction of a particle with a static potential using an iterative procedure that avoids the necessity for inversion of large matrices. The OPGF for a hierarchy of successively larger systems converging to the full system under study are thereby also obtained. We demonstrate the usefulness of the method, applying it to determine the bound-state spectrum and density of states of one particle interacting with mesoscopic size and extended two-dimensional systems. Applications to a variety of physical systems are briefly discussed.
Physical Review A, 1988
We develop a simple and general framework for understanding the relationships between absorption ... more We develop a simple and general framework for understanding the relationships between absorption and emission in multilevel systems (molecules, semiconductors, condensed matter, etc.) in and out of equilibrium. Conditions under which the absorption and emission spectra display mirror image symmetry are determined. The relationship between the absorption and emission cross sections at frequency co and temperature T, previously derived by Neporent and McCumber for thermally equilibrated systems, is generalized and a new derivation is presented which extends its range of application to systems out of equilibrium. This derivation requires only microscopic reversibility and that the optically coupled manifold of levels belonging to both initial and final electronic states are each in internal thermal equilibrium at the same temperature T. The initial and final (e.g. , ground and excited electronic) states need not be in equilibrium. If more than one excited-electronic-state manifold participates in the dynamics and these excited-electronic-state manifolds are not themselves in equilibrium, a somewhat more complicated relationship between absorption and emission can be obtained, provided that the internal degrees of freedom within the electronic-state manifolds are each in equilibrium at the same temperature. Effects of inhomogeneous broadening are examined. Good agreement is found between the Neporent-McCumber relationship and experimental absorption and emission spectra for the laser dyes rhodamine-6G and 2,5-biphenyloxazol PPO, and the solid-state laser crystal alexandrite. A new relationship between absorption and emission in direct-band-gap semiconductor materials is derived. This relationship allows us to calculate the emission from a direct-band-gap semiconductor provided the dependence of the band-gap energy on excitation level is not large. These relationships hold even when pumping conditions differ for emission and absorption experiments; the dependence of emission on excitation level can thereby be calculated. This permits the gain spectra of semiconductor diode lasers to be determined from their absorption spectra. In the limit that both the absorption and emission are measured for a thermally equilibrated nondegenerate direct-band-gap semiconductor system with identical pumping conditions for the absorption and emission experiments, our new relationship reduces to previous results.
Journal of Physics B: Atomic and Molecular Physics, 1974
A method for calculating charge exchange cross sections is generalized to provide a description o... more A method for calculating charge exchange cross sections is generalized to provide a description of p+H2 charge transfer processes. The assumptions and the conditions for the validity of the method are discussed. The results are compared with experiments on total charge transfer, capture into the 2S state of hydrogen and H2 are considered. Comparison with experiments and the predictions of Tuan and Gerjuoy is carried out.
Physical Review B, 1996
We present a variational formulation for the scattering of charged particles in a two-dimensional... more We present a variational formulation for the scattering of charged particles in a two-dimensional multiport structure and in the presence of a magnetic field. Our approach can be applied to systems with any local potential function and with very mild restrictions on the magnetic field; in particular, it is not restricted to homogeneous fields. We apply our approach to the calculation of the Hall, bend, and two-port resistances over large ranges of magnetic fields and Fermi energies for a system of crossed quantum wires confined by hard and soft walls, and in which a variety of impurity potentials have been placed. We find strong resonant features in these resistances for the case where a single repulsive impurity is present in the center of the intersection, whereas the resistances averaged over a random ensemble of potentials with nine impurities show a relatively weak effect. We also present results for scattering through a highly localized magnetic field in the intersection region.
Journal of Physics B-Atomic Molecular and Optical Physics, 1986
For dipole-allowed atomic transitions the radiative matrix element which defines the pressure-bro... more For dipole-allowed atomic transitions the radiative matrix element which defines the pressure-broadened atomic lineshape is only conditionally convergent. Using a commutator technique to redefine the integral, the authors isolate, and ultimately reject, the contribution of an indeterminate asymptotic surface integral that is associated with the energy normalisation of the continuum wavefunctions which describe the binary collision of the atom and its perturber. The remaining contributions, which are absolutely convergent, give the multichannel atomic lineshape which includes effects of non-adiabatic and inelastic scattering. Further, the authors show the relationship of the commutator integral to the exact requirements of close-coupled scattering theory for radiatively induced collisions. This scattering analysis suggests the interpretation of the convergent lineshape as an expression of multichannel inelastic collisions between field-dressed atomic states. This same interpretation applies both in the impact and the static limit. The authors make explicit comparisons which demonstrate the equivalence between the commutator integral and the numerical close-coupled results in the weak-field limit. They emphasize the static limit, well in the wings of the atomic line, where the Jablonski stationary-phase JWKB analysis is often applied to good effect.
Physical Review Letters, 1996
We show that the propagation equation for the slowly varying envelope of the electric field in a ... more We show that the propagation equation for the slowly varying envelope of the electric field in a homogeneous dispersive nonisotropic medium contains terms that rotate the 3D wave packet of an optical pulse propagating as an extraordinary wave about an axis perpendicular to the propagation vector. It also possesses Fresnel diffraction coefficients that depend not only on the refractive index but also its derivatives with respect to direction. An analytic expression for the slowly varying envelope is obtained for an initial Gaussian wave packet by keeping terms up to second order in the wave equation for the slowly varying envelope. {copyright} {ital 1996 The American Physical Society.}
Physical Review Letters, 1991
ABSTRACT
Physical Review E, 2013
The mean-field dynamics of a molecule with an induced dipole moment (e.g., a homonuclear diatomic... more The mean-field dynamics of a molecule with an induced dipole moment (e.g., a homonuclear diatomic molecule) in a deterministic and a stochastic (fluctuating) electric field is solved to obtain the decoherence properties of the system. The average (over fluctuations) electric dipole moment and average angular momentum as a function of time for a Gaussian white noise electric field are determined via perturbative and nonperturbative solutions in the fluctuating field. In the perturbative solution, the components of the average electric dipole moment and the average angular momentum along the deterministic electric field direction do not decay to zero, despite fluctuations in all three components of the electric field. This is in contrast to the decay of the average over fluctuations of a magnetic moment in a stochastic magnetic field with a Gaussian white noise magnetic field in all three components. In the nonperturbative solution, the component of the average electric dipole moment and the average angular momentum in the deterministic electric field direction also decay to zero.
Physical Review A, 1995
%'e investigate the convergence of diabatic scattering representations that make use of the commo... more %'e investigate the convergence of diabatic scattering representations that make use of the commonly applied closure relation (which eliminates first and second derivative coupling terms from the Schrodinger equation for the scattering wave function) to the adiabatic scattering formulations from which they are derived (wherein the internal basis states depend upon the collision coordinate). Numerical examples using a simple model of electron transport in a tapered waveguide are presented. The convergence of the diabatic to the adiabatic results with respect to the number of basis states is extremely slow. We discuss the significance of these findings to atomic and molecular scattering calculations.
Physical Review A, 1995
We report here measurements of two-body photoassociative ionization collisions between sodium ato... more We report here measurements of two-body photoassociative ionization collisions between sodium atoms within an ultranarrow velocity class selected from a well-collimated, thermal atomic beam. Doppler-shifted excitation of the Na(3s S»2. , F=1)~Na(5p P3/2) transition at 285 nm by a single-mode laser defines the narrow velocity class that subsequently populates the F=2 hyperfine level of the Na ground state by optical pumping. Probe laser beam excitation tuned near the Na(3s S»z, F=2)~Na(3p P3/2, F=3) transition produced photoassociative ionization with an average collision energy Ez corresponding to a temperature of 5.3 mK (Ex-zkT). We determine the rate constant for the process as a function of probe beam intensity and polarization.
Optics Letters, 1987
We show that there is a limit to the maximum efficiency achievable for correcting optical distort... more We show that there is a limit to the maximum efficiency achievable for correcting optical distortion (beam healing) using phase conjugation. This limit is quantum thermodynamic and stems from the impossibility of reducing the beam entropy by a lossless retrace of the phase aberrator.
Physical Review A, 2007
Inelastic collisions of ultracold atoms or molecules are analyzed using very general arguments. I... more Inelastic collisions of ultracold atoms or molecules are analyzed using very general arguments. In free space, the deactivation rate can be enhanced or suppressed together with the scattering length of the corresponding elastic collision via a Feshbach resonance, and by interference of deactivation of the closed and open channels. In reduced dimensional geometries, the deactivation rate decreases with decreasing collision energy and does not increase with resonant elastic scattering length. This has broad implications; e.g., stabilization of molecules in a strongly confining two-dimensional optical lattice, since collisional decay of excited states due to inelastic collisions is suppressed. The relation of our results to the Lieb-Liniger model for bosonic atoms is addressed.
Optics Communications, 2004
Recent experimental developments in material sciences have generated hope that it will be possibl... more Recent experimental developments in material sciences have generated hope that it will be possible to devise optical media where the difference in group velocity between the fundamental and third harmonic may be strongly suppressed. Under these circumstances both pulses would travel together over a long distance. This would lead to an enhancement of the generation process, and hence strong focusing and/or using ultra-short pulses might not be crucial. If the perfect phase matching condition is assumed, the only remaining mechanisms to decrease efficiency are self and cross phase modulation. Here we suggest that, instead of exactly matching wave vectors, we admit a small mismatch and show how it can be tailored to compensate for the cross phase modulation of the third harmonic by the fundamental during the generation process. This is very beneficial for the efficiency of third harmonic generation, even increasing it by a factor of two or more.
Physical Review E, 2005
We find two-component optical solitons in a nonlinear waveguide with a Bragg grating, including K... more We find two-component optical solitons in a nonlinear waveguide with a Bragg grating, including Kerr effects and third-harmonic generation ͑THG͒. The model may be realized in temporal and in spatial domains. Two species of fundamental gap solitons ͑GSs͒ are found. The first ͑"THG-gap soliton"͒ has the bulk of its energy at the fundamental frequency ͑FF͒ and a lesser part in the third-harmonic ͑TH͒ band. The FF part of the soliton is always single humped; the TH part may be single or double humped. Stability domains for quiescent and moving THG-gap solitons strongly shrink with increase of velocity. The second species is the usual ͑"simple"͒ GS, sitting entirely in the TH band. More complex solutions are also found, in the form of a bound state of a THG-gap soliton and two simple GSs, with a finite binding energy. When a THG-gap soliton is unstable, the instability is oscillatory. It may ultimately cause the THG-gap soliton to throw off some radiation and evolve into a localized structure with the FF and TH components out of phase, with or without internal oscillations. Stable solitons feature an excited state ͑i.e., they support a localized eigenmode͒.
Advanced Solid State Lasers, 1991
We shall describe the spectrum, temporal dependence, and efficiency of intracavity second harmoni... more We shall describe the spectrum, temporal dependence, and efficiency of intracavity second harmonic generation ring lasers (ISHRL). We solve for the dynamics of ISHRL containing a homogeneously broadened gain medium, a phasematched doubling medium, a tuner, and a dichroic output coupler (see Fig. 1). The dynamics of each of these elements is described analytically (except for the doubling element, which must be solved numerically if the slowly varying envelope of the electric field is complex, i.e., if FM modulation is present). We show that cw single-mode operation of ISHRL is stable against the growth of additional modes due to amplitude-modulated (AM) fluctuations of the fundamental, however, frequency-modulated (FM) fluctuations are not damped. Cw operation tends to single longitudinal mode output provided no frequency modulation arises. Multimode frequency-modulated cw operation can be achieved. Methods for achieving anti-modelocked laser output are described. We consider the temporal dependence and efficiency of Q-switched ISHRL. Comparision with the Q-switched fundamental laser (not containing second harmonic generation) demonstrates that ISHRL can be even more efficient than the fundamental laser. General principies for assuring controlled intracavity fundamental intensity buildup are presented. Injection of multimode pulses and modelocked pulses into Q-switched ISHRL are considered.
Ultrafast Phenomena IV, 1984
In the passive mode-locking of a laser, the leading edge of the mode-locked pulse is shaped by th... more In the passive mode-locking of a laser, the leading edge of the mode-locked pulse is shaped by the rapid reduction of loss due to absorption saturation of the absorbing material. There are two mechanisms in general use for shaping the trailing edge of a mode-locked pulse. For gain media which saturate easily, such as organic dyes, the saturation of the gain which follows the peak of the pulse shapes the lagging edge of the pulse [1]. For gain media which cannot be saturated by an individual mode-locked pulse, because the saturation energy is too high, the trailing edge of the pulse continues to see gain and is not suppressed. For solid-state lasers (e.g., alexandrite, ruby, Nd:YAG, and Nd:Glass, etc.) which have high saturation energy, a saturable absorber with a fast relaxation time is used since a pulse with energy greater than the absorber’s saturation energy will experience the least loss in propagating through the cavity when the pulse length is shorter than the absorber’s relaxation time [2]. Therefore, by this mechanism the pulsewidths of broadly tunable, solid-state mode-locked lasers are limited by the relaxation times of saturable absorbers rather than the lasing bandwidth of the media.
Advanced Solid State Lasers, 1989
Second harmonic conversion (SHG) of Alexandrite is an effective means of obtaining tunable high p... more Second harmonic conversion (SHG) of Alexandrite is an effective means of obtaining tunable high peak power over the wavelength range 350-400nm. However, external SHG requires high intensity for efficient conversion and optical damage problems can result. An alternative is to utilize high intracavity intensities for conversion while at the same time use the SHG process as a power limiter for the intracavity fundamental laser beam. Intracavity SHG in a unidirectional Alexandrite ring laser with the only output at the second harmonic frequency was studied. Experimental results and their comparison with modeling studies of such a process will be discussed.
Coherence and Quantum Optics VI, 1990
Physical Review A, 1989
We present a method for e%ciently calculating the one-particle Green's function (OPCxF) for the i... more We present a method for e%ciently calculating the one-particle Green's function (OPCxF) for the interaction of a particle with a static potential using an iterative procedure that avoids the necessity for inversion of large matrices. The OPGF for a hierarchy of successively larger systems converging to the full system under study are thereby also obtained. We demonstrate the usefulness of the method, applying it to determine the bound-state spectrum and density of states of one particle interacting with mesoscopic size and extended two-dimensional systems. Applications to a variety of physical systems are briefly discussed.
Physical Review A, 1988
We develop a simple and general framework for understanding the relationships between absorption ... more We develop a simple and general framework for understanding the relationships between absorption and emission in multilevel systems (molecules, semiconductors, condensed matter, etc.) in and out of equilibrium. Conditions under which the absorption and emission spectra display mirror image symmetry are determined. The relationship between the absorption and emission cross sections at frequency co and temperature T, previously derived by Neporent and McCumber for thermally equilibrated systems, is generalized and a new derivation is presented which extends its range of application to systems out of equilibrium. This derivation requires only microscopic reversibility and that the optically coupled manifold of levels belonging to both initial and final electronic states are each in internal thermal equilibrium at the same temperature T. The initial and final (e.g. , ground and excited electronic) states need not be in equilibrium. If more than one excited-electronic-state manifold participates in the dynamics and these excited-electronic-state manifolds are not themselves in equilibrium, a somewhat more complicated relationship between absorption and emission can be obtained, provided that the internal degrees of freedom within the electronic-state manifolds are each in equilibrium at the same temperature. Effects of inhomogeneous broadening are examined. Good agreement is found between the Neporent-McCumber relationship and experimental absorption and emission spectra for the laser dyes rhodamine-6G and 2,5-biphenyloxazol PPO, and the solid-state laser crystal alexandrite. A new relationship between absorption and emission in direct-band-gap semiconductor materials is derived. This relationship allows us to calculate the emission from a direct-band-gap semiconductor provided the dependence of the band-gap energy on excitation level is not large. These relationships hold even when pumping conditions differ for emission and absorption experiments; the dependence of emission on excitation level can thereby be calculated. This permits the gain spectra of semiconductor diode lasers to be determined from their absorption spectra. In the limit that both the absorption and emission are measured for a thermally equilibrated nondegenerate direct-band-gap semiconductor system with identical pumping conditions for the absorption and emission experiments, our new relationship reduces to previous results.
Journal of Physics B: Atomic and Molecular Physics, 1974
A method for calculating charge exchange cross sections is generalized to provide a description o... more A method for calculating charge exchange cross sections is generalized to provide a description of p+H2 charge transfer processes. The assumptions and the conditions for the validity of the method are discussed. The results are compared with experiments on total charge transfer, capture into the 2S state of hydrogen and H2 are considered. Comparison with experiments and the predictions of Tuan and Gerjuoy is carried out.
Physical Review B, 1996
We present a variational formulation for the scattering of charged particles in a two-dimensional... more We present a variational formulation for the scattering of charged particles in a two-dimensional multiport structure and in the presence of a magnetic field. Our approach can be applied to systems with any local potential function and with very mild restrictions on the magnetic field; in particular, it is not restricted to homogeneous fields. We apply our approach to the calculation of the Hall, bend, and two-port resistances over large ranges of magnetic fields and Fermi energies for a system of crossed quantum wires confined by hard and soft walls, and in which a variety of impurity potentials have been placed. We find strong resonant features in these resistances for the case where a single repulsive impurity is present in the center of the intersection, whereas the resistances averaged over a random ensemble of potentials with nine impurities show a relatively weak effect. We also present results for scattering through a highly localized magnetic field in the intersection region.
Journal of Physics B-Atomic Molecular and Optical Physics, 1986
For dipole-allowed atomic transitions the radiative matrix element which defines the pressure-bro... more For dipole-allowed atomic transitions the radiative matrix element which defines the pressure-broadened atomic lineshape is only conditionally convergent. Using a commutator technique to redefine the integral, the authors isolate, and ultimately reject, the contribution of an indeterminate asymptotic surface integral that is associated with the energy normalisation of the continuum wavefunctions which describe the binary collision of the atom and its perturber. The remaining contributions, which are absolutely convergent, give the multichannel atomic lineshape which includes effects of non-adiabatic and inelastic scattering. Further, the authors show the relationship of the commutator integral to the exact requirements of close-coupled scattering theory for radiatively induced collisions. This scattering analysis suggests the interpretation of the convergent lineshape as an expression of multichannel inelastic collisions between field-dressed atomic states. This same interpretation applies both in the impact and the static limit. The authors make explicit comparisons which demonstrate the equivalence between the commutator integral and the numerical close-coupled results in the weak-field limit. They emphasize the static limit, well in the wings of the atomic line, where the Jablonski stationary-phase JWKB analysis is often applied to good effect.
Physical Review Letters, 1996
We show that the propagation equation for the slowly varying envelope of the electric field in a ... more We show that the propagation equation for the slowly varying envelope of the electric field in a homogeneous dispersive nonisotropic medium contains terms that rotate the 3D wave packet of an optical pulse propagating as an extraordinary wave about an axis perpendicular to the propagation vector. It also possesses Fresnel diffraction coefficients that depend not only on the refractive index but also its derivatives with respect to direction. An analytic expression for the slowly varying envelope is obtained for an initial Gaussian wave packet by keeping terms up to second order in the wave equation for the slowly varying envelope. {copyright} {ital 1996 The American Physical Society.}
Physical Review Letters, 1991
ABSTRACT
Physical Review E, 2013
The mean-field dynamics of a molecule with an induced dipole moment (e.g., a homonuclear diatomic... more The mean-field dynamics of a molecule with an induced dipole moment (e.g., a homonuclear diatomic molecule) in a deterministic and a stochastic (fluctuating) electric field is solved to obtain the decoherence properties of the system. The average (over fluctuations) electric dipole moment and average angular momentum as a function of time for a Gaussian white noise electric field are determined via perturbative and nonperturbative solutions in the fluctuating field. In the perturbative solution, the components of the average electric dipole moment and the average angular momentum along the deterministic electric field direction do not decay to zero, despite fluctuations in all three components of the electric field. This is in contrast to the decay of the average over fluctuations of a magnetic moment in a stochastic magnetic field with a Gaussian white noise magnetic field in all three components. In the nonperturbative solution, the component of the average electric dipole moment and the average angular momentum in the deterministic electric field direction also decay to zero.
Physical Review A, 1995
%'e investigate the convergence of diabatic scattering representations that make use of the commo... more %'e investigate the convergence of diabatic scattering representations that make use of the commonly applied closure relation (which eliminates first and second derivative coupling terms from the Schrodinger equation for the scattering wave function) to the adiabatic scattering formulations from which they are derived (wherein the internal basis states depend upon the collision coordinate). Numerical examples using a simple model of electron transport in a tapered waveguide are presented. The convergence of the diabatic to the adiabatic results with respect to the number of basis states is extremely slow. We discuss the significance of these findings to atomic and molecular scattering calculations.
Physical Review A, 1995
We report here measurements of two-body photoassociative ionization collisions between sodium ato... more We report here measurements of two-body photoassociative ionization collisions between sodium atoms within an ultranarrow velocity class selected from a well-collimated, thermal atomic beam. Doppler-shifted excitation of the Na(3s S»2. , F=1)~Na(5p P3/2) transition at 285 nm by a single-mode laser defines the narrow velocity class that subsequently populates the F=2 hyperfine level of the Na ground state by optical pumping. Probe laser beam excitation tuned near the Na(3s S»z, F=2)~Na(3p P3/2, F=3) transition produced photoassociative ionization with an average collision energy Ez corresponding to a temperature of 5.3 mK (Ex-zkT). We determine the rate constant for the process as a function of probe beam intensity and polarization.
Optics Letters, 1987
We show that there is a limit to the maximum efficiency achievable for correcting optical distort... more We show that there is a limit to the maximum efficiency achievable for correcting optical distortion (beam healing) using phase conjugation. This limit is quantum thermodynamic and stems from the impossibility of reducing the beam entropy by a lossless retrace of the phase aberrator.