Showing papers on "Resonance published in 1989"

Structure and mechanism

Abstract: Enzyme Modifications for Nuclear Magnetic Resonance Studies: J.T. Gerig, Fluorine Nuclear Magnetic Resonance of Fluorinated Ligands. D.M. LeMaster, Deuteration in Protein-Proton Magnetic Resonance. D.C. Muchmore, L.P. McIntosh, C.B. Russell, D.E. Anderson, and F.W. Dahlquist, Expression and Nitrogen-15 Labeling of Proteins for Proton and Nitrogen-15 Nuclear Magnetic Resonance. D.W. Hibler, L. Harpold, M. Dell'Acqua, T. Pourmotabbed, J.A. Gerlt, J.A. Wilde, and P.H. Bolton, Isotopic Labeling with Hydrogen-2 and Carbon-13 to Compare Conformations of Proteins and Mutants Generated by Site-Directed Mutagenesis, I. P.A. Kosen, Spin Labeling of Proteins. Protein Structure: K. W*aduthrich, Determination of Three-Dimensional Protein Structures in Solution by Nuclear Magnetic Resonance: An Overview. V.J. Basus, Proton Nuclear Magnetic Resonance Assignments. M. Billeter, Computer-Assisted Resonance Assignments. I.D. Kuntz, J.F. Thomason, and C.M. Oshiro, Distance Geometry. R.M. Scheek, W.F. van Gunsteren, and R. Kaptein, Molecular Dynamics Simulation Techniques for Determination of Molecular Structures from Nuclear Magnetic Resonance Data. R.B. Altman and O. Jardetzky, Heuristic Refinement Method for Determination of Solution Structure of Proteins from Nuclear Magnetic Resonance Data. I. Bertini, L. Banci, and C. Luchinat, Proton Magnetic Resonance of Paramagnetic Metalloproteins. H.J. Vogel, Phosphorus-31 Nuclear Magnetic Resonance of Phosphoproteins. J.A. Wilde, P.H. Bolton, D.W. Hibler, L. Harpold, T. Pourmotabbed, M. Dell'Acqua, and J.A. Gerlt, Isotopic Labeling with Hydrogen-2 and Carbon-13 to Compare Conformations of Proteins and Mutants Generated by Site-Directed Mutagenesis, II. Enzyme Mechanisms: D.G. Gorenstein and C.B. Post, Phosphorus-31 Nuclear Magnetic Resonance of Enzyme Complexes: Bound Ligand Structure, Dynamics, and Environment. C.R. Sanders II and M.-D. Tsai, Ligand*b1Protein Interactions via Nuclear Magnetic Resonance of Quadrupolar Nuclei. P.R. Rosevear and A.S. Mildvan, Ligand Conformations and Ligand*b1Enzyme Interactions as Studied by Nuclear Overhauser Effect. B.D. Nageswara Rao, Determination of Equilibrium Constants of Enzyme-Bound Reactants and Products by Nuclear Magnetic Resonance. J.M. Risley and R.L. Van Etten, Mechanistic Studies Utilizing Oxygen-18 Analyzed by Carbon-13 and Nitrogen-15 Nuclear Magnetic Resonance Spectroscopy. J.J. Villafranca, Positional Isotope Exchange Using Phosphorus-31 Nuclear Magnetic Resonance. J.J. Villafranca, Paramagnetic Probes of Macromolecules. In Vivo Studies of Enzymatic Material: S.M. Cohen, Enzyme Regulation of Metabolic Flux. J.S. Cohen, R.C. Lyon, and P.F. Daly, Monitoring Intracellular Metabolism by Nuclear Magnetic Resonance. Appendix: Computer Programs Related to Nuclear Magnetic Resonance: Availability, Summaries, and Critiques. Each chapter includes references. Author Index. Subject Index.

Composite structures for the enhancement of nonlinear-optical susceptibility

Abstract: Calculations of the nonlinear-optical behavior are developed for model composites of nanospheres with a metallic core and nonlinear shell or with a nonlinear core and metallic shell suspended in a nonlinear medium. Optical phase conjugation is shown to be enhanced from each nonlinear region because the optical field can be concentrated in both the interior and the exterior neighborhoods of the particle and magnified at the surface-mediated plasmon resonance. For the model composite with a metallic core, a limited range of resonance tunability can be achieved by adjustment of shell thickness; the frequency range is dependent on the dielectric dispersion of the metal. For the composite with a metallic shell instead of a metallic core, this restriction is reduced so that tunability from ultraviolet to infrared can be attained. Enhancement of the phase-conjugate signal is calculated for the electrostrictive mechanism dominant in the microsecond time scale and for the electronic mechanism dominant in the picosecond time scale. Calculations based on the dielectric functions for gold and for aluminum indicate that phase-conjugate reflectivity enhancements of 108 can be achieved. The imaginary components of the composite dielectric functions are shown to limit the magnitude of the field enhancement at the surface-plasmon resonance and determine the absorption and figure of merit of the composite.

Electron–vibration coupling in semiconductor clusters studied by resonance Raman spectroscopy

Abstract: The resonance Raman spectrum of 45(+−3) A diameter CdSe clusters was measured. The incident photons were resonant with the HOMO–LUMO transition in the clusters. At low temperature, one mode at 205 cm−1 is observed, as well as two overtones, with the integrated areas under these peaks in the ratio of 9:3:1. This mode is assigned as the longest wavelength longitudinal optical vibration of the cluster. The strength of the coupling between the lowest electronic excited state and the LO vibration is found to be 20 times weaker in these clusters than in the bulk solid. The CdSe cluster resonance Raman spectrum is shown to be consistent with the recently measured homogeneous cluster absorption spectrum.

Guiding-center-drift resonance in a periodically modulated two-dimensional electron gas.

Abstract: A theory is developed for the recently discovered magnetoresistance oscillations in a two-dimensional electron gas subject to a weak periodic potential. The effect is explained as a resonance between the periodic cyclotron orbit motion and the oscillating E\ifmmode\times\else\texttimes\fi{}B drift of the orbit center induced by a potential grating.

RF Spectroscopy in an Atomic Fountain

Abstract: We have created an atomic fountain starting with a sample of laser cooled Na atoms. Excitation of the atoms between the F=1, mF=0 and F=2, mF=0 ground states have an observed linwidth of 2.0 Hz at ν = 1,772,626,129. +1/−10 Hz using the Ramsey resonance technique.

Magnetic resonance determination of the antiferromagnetic coupling of Fe layers through Cr.

Abstract: Variable frequency ferromagnetic resonance (FMR) has been used to directly observe the coupled resonance modes in single-crystal Fe/Cr/Fe(001) sandwiches grown by molecular-beam epitaxy. Magnetization M and magnetoresistance measurements also were carried out on these samples, which exhibited antiferromagnetic (AF) layer alignment for 12 A\r{}lt(Cr)25 A\r{}. The FMR data reveal two resonance modes with complex frequency dependences for the AF-aligned samples. The detailed FMR and M vs H behavior can be quantitatively explained by an AF coupling parameter J which has a thickness dependence peaked about t(Cr)=16 A\r{}.

Theory of two‐wave mixing gain enhancement in photorefractive InP:Fe: A new mechanism of resonance

Abstract: We present a new model (including both temperature and electron‐hole effects) of two‐beam coupling in photorefractive semiconductors under an external dc field E0. This model predicts that the exponential gain Γ can exhibit an intensity‐dependent resonant behavior, yielding a π/2 phase shift of the space‐charge field with respect to the incident fringe pattern. This optimum intensity strongly depends on crystal temperature but it is practically independent of the grating period. As an illustration this model is applied to InP:Fe. In this case the resonance occurs when the hole photoionization rate and the electron thermal emission rate are equal. Values of Γ as high as 20 cm−1 at 1.06 μm, for a fringe spacing of 15 μm and E0 =10 kV/cm, are predicted. The comparison between theory and experimental data requires taking into account the variation of the pump intensity throughout the sample (due to optical absorption), which reduces the volume where the resonance condition is fulfilled; in this way a satisfac...

Test of the Linearity of Quantum Mechanics by RF Spectroscopy of the 9BE+ Ground State

Abstract: The agreement between quantum-mechanical predictions and experiments has so firmly established the validity of quantum mechanics that we might question the need for further tests. For example, the observed energy levels of hydrogen are in excellent agreement with quantum-mechanical predictions. However, to a large extent this agreement can be regarded more as a test of the specific Hamiltonian used, than of quantum mechanics itself. It should be possible to test the basic framework of quantum mechanics independently of and to much greater accuracy than that provided by such specific predictions. Recently, Weinberg1 has formulated a general framework which introduces nonlinear corrections to quantum mechanics and enables such a test. He suggested that a sensitive test could be made for the presence of such a nonlinearity by slowly driving a resonant transition which transfers a quantum system from one state to another. The effect of the nonlinearity is to make the effective resonance frequency a function of the state probabilities. Thus, the resonance frequency changes as the quantum system is driven from one state to the other, and the applied perturbation (assumed to be monochromatic) cannot stay in resonance through the entire transition. The system will never be driven completely to the other state. This effect would not be observed, that is, the transition could still be driven, if the maximum frequency shift were much less than 1/T. Here, T is the time required to drive the transition if there is no nonlinearity.

Vacuum ultraviolet resonance Raman studies of the excited electronic states of ethylene

Abstract: A resonance Raman study of ethylene has been performed with the use of excitation wavelengths ranging from 200 to 141 nm. Excitation resonant with the V(ππ*) state results in Raman spectra exhibiting intensity in the C=C stretching vibration, the CH2 symmetric scissors vibration, the CH2 torsional vibration and the CH2 out‐of‐plane wagging vibrations. These spectra confirm that the V state is strongly twisted about the C–C bond. They also indicate that the C=CH2 groups are no longer planar in the V state. Resonance with the (π3s) and (π3p) Rydberg transitions results in spectra exhibiting much less intensity in the torsional vibration, the CH2 symmetric scissors vibration and the CH2 wagging vibrations. The spectrum obtained in resonance with the (π3d) Rydberg transitions once again exhibits activity in the CH2 symmetric scissors mode.

Application of nuclear magnetic resonance pore structure analysis to porous silica glass

Abstract: The internal pore structure of a series of porous silica glasses has been investigated using nuclear magnetic resonance (NMR). Longitudinal and transverse relaxation of protons in deionized water confined to the pores of the samples has been measured and interpreted to provide pore size distributions. Two sets of leached, phase‐separated porous glasses were used: the first nominally bimodal, the second with a more uniform pore space with pore sizes varying from 32 to 1350 A. Our results provide a stringent test of NMR relaxation as a method for pore size analysis. NMR relaxation experiments were performed on one sample as a function of the amount of water imbibed confirming the validity of the theoretical model used to interpret the magnetic resonance data.

Measurement of internuclear distances in polycrystalline solids: Rotationally enhanced transfer of nuclear spin magnetization

Abstract: A magic angle spinning (MAS) NMR technique for measurement of the distance between two homonuclear sites separated by as much as 0.5 nm is demonstrated. This is achieved by proton decoupling during the magnetization exchange process, greatly attenuating the influence of abundant nuclear spins, selective isotopic labeling of both sites of interest, so that the system may be approximated as a set of magnetically dilute coupled spin pairs, and MAS with matching of the rotational resonance condition. Tyrosine ethyl ester (TEE), carbon 13 labeled at both the -CH{sub 2}- of the ester moiety and at the 4{prime}-OH aromatic carbon is used as a demonstration of the technique. Calculated data is compared to experimental data.

Excited state structure and femtosecond ring‐opening dynamics of 1,3‐cyclohexadiene from absolute resonance Raman intensities

Abstract: Resonance Raman spectra of 1,3‐cyclohexadiene have been obtained with excitation wavelengths ranging from 300 to 253 nm. The absolute excitation profiles were analyzed to determine the initial dynamics that occur following photoexcitation in the lowest energy 260 nm 1B2 absorption band. The initial atomic displacements parallel the Woodward–Hoffmann, symmetry‐allowed, ring‐opening pathway towards all‐cis‐hexatriene. The potential surface displacements in the optically prepared 1B2 excited state are, however, a small fraction of the total distance along the reaction coordinate. The low absolute scattering cross sections indicate an excited state dephasing time of 10−14 s, and the fluorescence quantum yield of 2×10−6 shows that the total dephasing rate is dominated by ultrafast internal conversion. The Gaussian homogeneous line shape indicates a nonexponential excited electronic state population decay. We attribute these observations to an allowed crossing of the 1B2 state with a second excited 2A1 state that is responsible for the subsequent excited‐state ring‐opening reaction.

A spin dependent recombination study of radiation induced defects at and near the Si/SiO/sub 2/ interface

Abstract: A novel electron spin resonance technique, spin-dependent recombination (SDR), permits extremely rapid, high-signal-to-noise-ratio electron spin resonance (ESR) measurements of electrically active radiation damage centers in (relatively) hard MOS transistors in integrated circuits. SDR was used to observe the radiation-induced buildup of P/sub bo/ and E' centers at relatively low concentration in individual MOSFETs in integrated circuits with

Resonant optical transmission and coupling in phase‐locked diode laser arrays of antiguides: The resonant optical waveguide array

Abstract: Uniform linear arrays of antiguides have 100% optical transmission between elements when the interelement spacing is an integer number of leaky wave half‐wavelengths in the lateral direction. Resonant in‐phase‐mode and out‐of‐phase‐mode coupling occurs when the number of half‐wavelengths is odd and even, respectively. Such devices are called resonant optical waveguide (ROW) arrays. The discrimination between the resonant array mode and adjacent array modes reaches a maximum in close proximity to the resonance. An AlGaAs/GaAs ROW diode laser array operating close to resonance is demonstrated. Devices with virtually uniform near‐field intensity profiles operate in stable, diffraction‐limited in‐phase modes to drive levels in excess of three times threshold.

Resonant Nonlinear Interactions of Light with Matter

Abstract: 1. Resonant Multiphoton Interactions and the Generalized Two-Level System.- 1.1 The Basic Equations Describing the Evolution of Radiation Interacting with Matter.- 1.2 The Truncated Equations for the Density Matrix.- 1.2.1 The Two-Level Model and the First Approximation of the Averaging Method.- 1.2.2 Second-Order Resonances and an Example of the Simultaneous Realization of Two Resonance Conditions.- 1.2.3 The Hamiltonian of the Averaged Motion.- 1.2.4 The Truncated Equations for Resonances of Arbitrary Order Involving Many Levels.- 1.3 Polarization of Matter and the Generalized Dipole Moment.- 1.4 The Generalized Two-Level System.- 2. The Molecular Response to the Resonant Effects of Quasimonochromatic Fields.- 2.1 The Change of Populations of the Generalized Two-Level System in Quasimonochromatic Fields.- 2.1.1 Saturation of Populations of Resonant Levels and the Effect Which the Level Shift Under the Influence of Light Has on Saturation.- 2.1.2 Balance Equations and Interference of Transition Probability Amplitudes in Resonant Parametric Interactions.- 2.2 Susceptibility in Incoherent Multiphoton Processes.- 2.2.1 Expressions for Susceptibility.- 2.2.2 The Imaginary Part of Susceptibility as a Function of Fields and the Energy Absorbed by Matter.- 2.2.3 The Real Part of Susceptibility for the Single-Photon Resonance.- 2.2.4 The Real Part of Susceptibility for Two-Photon Absorption (TPA) and Stimulated Raman Scattering (SRS).- 2.2.5 The Real Part of Susceptibility Generated by Light Pulses.- 2.3 Spectroscopy of Polarizabilities of Excited States.- 2.4 Molecular Response for Resonant Parametric Interactions.- 3. The Dynamics of Quantum Systems for Resonant Interactions with Strong Nonstationary Fields.- 3.1 The Equation of Motion and Its Properties.- 3.1.1 The Specific Features of the Relaxation of the System in a Strong Quasi-Resonant Field.- 3.1.2 The Equation of Population Motion.- 3.1.3 Equation of Population Dynamics for Two-Photon Processes.- 3.2 Amplitude Modulation for Exact Frequency Resonance, ? ? 0 (Exact Solutions).- 3.2.1 Equal Relaxation Times (T = ?).- 3.2.2 The Case of Unequal Relaxation Times (T ? ?).- 3.2.3 Relaxation in the Field of a Single Pulse for T ? ?, and Methods for Exact Solutions.- 3.3 Amplitude-Frequency Modulation of the Field (Exact Solutions).- 3.3.1 The Case of Equal Relaxation Times (T = ?).- 3.3.2 The Non-Equal Relaxation Times (T ? ?).- 3.4 Approximate Solutions in Various Limiting Cases.- 3.5 Relaxation in a Stationary Field.- 3.6 Polarization Dynamics in a Nonstationary Field.- 4. Polarization of Resonant Media.- 4.1 Nonlinear Polarization of Gaseous Media.- 4.1.1 Probability of Stimulated Multiphoton Transitions and Polarization of Freely Self-Orienting Systems.- 4.1.2 The Local Coherence of Parametric Interaction.- 4.1.3 Influence of the Doppler Effect on the Shape of the Absorption Line for Multiphoton Interactions.- 4.2 Dispersion Properties of the Resonant Susceptibility of Media with Identically Oriented Particles.- 4.3 The Equation for the Nonlinear Susceptibility for the Single-Photon Resonance.- 4.4 The Properties of Spatial Harmonics of Susceptibility.- 4.4.1 Relationships Between Direct and Mixed Susceptibilities.- 4.4.2 The Connection Between Susceptibilities ?, a and b.- 4.4.3 Potential Function for Susceptibilities.- 5. Structure of One-Dimensional Waves for the Single-Photon Resonance.- 5.1 Conservation Laws for One-Dimensional Waves in Resonant Media.- 5.2 Stationary Oscillations in a Layer of Identical Molecules Without Distributed Losses.- 5.3 Stationary Oscillations in a Layer of Identical Molecules in the Presence of Distributed Losses.- 5.4 Rotation of Polarization Planes of Countertravelling Waves in an Isotropic Nonlinear Medium.- 6. Three-Photon Resonant Parametric Processes.- 6.1 Addition and Doubling qf Frequencies for a Transition Frequency in Matter That Coincides with the Sum Frequency or the Frequency of the Harmonic.- 6.1.1 Addition and Doubling of Frequencies in a Medium with Identically Oriented Molecules.- 6.1.2 On Resonant Frequency Doubling in Vapors and Gases.- 6.2 Generation of the Second Harmonic of Resonant Pumping...- 6.3 Resonant Division of Frequency.- 6.4 Generation of the Difference Frequency During Stimulated Raman Scattering.- 6.4.1 Generation of Resonant Radiation During SRS in a Medium Consisting of Identically Oriented Molecules.- 6.4.2 Generation of the Difference Frequency During SRS in Gases.- 6.4.3 Generation of the Difference Frequency During SRS in the Presence of a Nonuniform Electrostatic Field.- 7. Four-Photon Resonant Parametric Interactions (RPI).- 7.1 Anti-Stokes Stimulated Raman Scattering.- 7.1.1 Specific Features of ASRS.- 7.1.2 Basic Equations.- 7.1.3 Spatial Distribution of the Anti-Stokes Component.- 7.1.4 Energy Characteristics of ASRS.- 7.1.5 The Experimental Analysis of Energy Characteristics.- 7.2 The Influence of Four-Photon RPIs on the Dynamics of the Stokes Components of SRS.- 7.2.1 Generation of the Stokes Components of SRS During Biharmonic Pumping.- 7.2.2 The Effect of Strong Pumping TPA on Weak Pumping SRS.- 7.2.3 Discussion of Experimental Results.- 7.3 Radiation Frequency Transformation in Four-Photon RPIs Based on Pumping Field TPA and SRS.- 7.3.1 Introductory Remarks and Basic Equations.- 7.3.2 Generation of the Difference Frequency During TPA.- 7.3.3 Generation of the Sum Frequency During TPA.- 7.3.4 The Effect of Wave Detuning.- 7.3.5 Transformation Length and Effect of Population Saturation.- 7.3.6 Four-Photon RPI's Based on SRS of the Pumping Field.- 7.3.7 Generation of the Difference Frequency During SRS...- 7.3.8 Generation of the Sum Frequency During SRS.- 7.3.9 Discussion.- 7.4 On Soft Excitation of Stimulated Two-Photon Radiation.- 8. Self-Action of Light Beams Caused by Resonant Interaction with the Medium.- 8.1 Specific Features and Threshold Characteristics of Self-Focussing in an Absorbing Medium.- 8.1.1 The Equation for the Beam Radius.- 8.1.2 The Threshold for Weak Attenuation.- 8.1.3 The Threshold for Strong and Intermediate Attenuation.- 8.2 The "Weak" Self-Focussing and Self-Defocussing of a Gaussian Beam in an Absorbing Medium.- 8.3 Self-Bending of Trajectories of Asymmetric Light Beams in Nonlinear Media.- 8.4 Conditions for the Existence of Self-Action Caused by Resonant Absorption.- 8.5 Self-Action of Light Caused by Stimulated Raman Scattering.- 8.5.1 Formation of a Thin Lens in the Region of SRS-Transformation.- 8.5.2 The Threshold of SRS Self-Focussing and Self-Bending..- 8.6 Self-Action Effects at Nonlinear Interface.- 8.6.1 Nonlinear Properties of Interfaces.- 8.6.2 The Main Equations and Conditions.- 8.6.3 Effects at "Positive" Nonlinearity.- 8.6.4 Experiments on a Nonlinear Interface.- 8.6.5 Effects at "Negative" Nonlinearity Longitudinally Inhomogeneous Traveling Waves (LITW).- 8.6.6 Theorems of LITW Existence for Arbitrary Kinds of Nonlinearity.- 8.7 Optical Bistability Based on Mutual Self-Action of Counterpropagating Light Beams.- 8.7.1 Experimental Observation of Bistability Based on Self-Trapping.- 8.7.2 Mutual Self-Action of Counterpropagating Beams in the General Case.- References.

Nonlinear Faraday resonance in a box with a square base

Abstract: Surface wave motions in a container with a square base, which is subject to a vertical oscillation, are considered when the amplitude of the oscillation is small and the frequency of the oscillation is close to twice the natural frequency of the system. Subcritical wave motions are found for single modes as well as mixed modes. Here, single modes are described by either one of the two horizontal coordinates whereas mixed modes depend on both coordinates. It is found that in some subcritical region a stable single mode and a stable mixed mode coexist, producing complex basins of attraction.