Showing papers on "Resonance published in 1987"
TL;DR: In this paper, the frequency response of a group of 1.3 μm InGaAsP vapor-phase-regrown buried heterostructure lasers of various cavity lengths is analyzed by fitting the measured response curves.
Abstract: The frequency response of a group of 1.3 μm InGaAsP vapor-phase-regrown buried heterostructure lasers of various cavity lengths is analyzed by fitting the measured response curves. The dependence of resonant frequency f 0 and damping rate \Gamma on bias power is determined. The differential gain coefficient for InGaAsP is determined as 3.5 \times 10^{-16} cm2. The damping rate is found to be proportional to the square of the resonant frequency with a proportionality factor which is independent of device geometry and facet reflectivity. The existence of such a universal relationship between \Gamma and f 0 and the observed magnitude of the damping rate is explained by the interband relaxation model of nonlinear gain.
306 citations
TL;DR: The experiments demonstrate that a particular ion (calcium) is apparently moved across the cell membrane in response to the DC and AC values of magnetic flux densities and the frequency derived from the cyclotron resonance theory.
Abstract: The hypothesis that movement of biological ions may be predicted by cyclotron resonance theory applied to cell membranes is tested in these experiments. Diatoms (Amphora coffeaeformis) were chosen as the biosystem since they move or don't move, depending on how much calcium is transported across the membrane. The experiments demonstrate that a particular ion (calcium) is apparently moved across the cell membrane in response to the DC and AC values of magnetic flux densities (B) and the frequency derived from the cyclotron resonance theory. A clear resonance is shown and a rather sharp frequency response curve is demonstrated. The experiments also show a dose response as the AC value of the flux density is varied, and that odd harmonics of the basic cyclotron frequency are also effective.
223 citations
TL;DR: In this paper, it is shown how the phenomenon of MHD surface wave resonance absorption can be described in simple terms, both physically and mathematically, by applying the thin flux tube equations to the finite-thickness transition layer which supports the surface wave.
Abstract: It is shown how the phenomenon of MHD surface wave resonance absorption can be described in simple terms, both physically and mathematically, by applying the 'thin flux tube equations' to the finite-thickness transition layer which supports the surface wave. The thin flux tubes support incompressible slow-mode waves that are driven by fluctuations in the total pressure which exist due to the presence of the surface wave. It is shown that the equations for the slow-mode waves can be reduced to a simple equation, equivalent to a driven harmonic oscillator. Certain field lines within the transition layer are equivalent to a harmonic oscillator driven at resonance, and neighboring field lines are effectively driven at resonance as long as a given condition is satisfied. Thus, a layer which secularly extracts energy from the surface wave develops. The analysis indicates that nonlinear effects may destroy the resonance which is crucial to the whole effect.
139 citations
TL;DR: In this article, the optical constants of a thin gold film over primarily the visible region of the spectrum were measured using the surface plasmon-polariton resonance condition in the attenuated total-reflection configuration.
Abstract: Measurements are presented of the optical constants of a thin gold film over primarily the visible region of the spectrum using the surface plasmon-polariton resonance condition in the attenuated total-reflection configuration. Using this technique precise results are obtained and these are compared with those found using other experimental methods and also with the classical free-electron model.
112 citations
TL;DR: In this article, the presence of an axially symmetric angular distribution of energetic electrons in hot plasmas can be detected by measuring the linear polarisation of the X-ray lines emitted from collisionally excited levels of multiply charged ions.
Abstract: The presence of an axially symmetric angular distribution of energetic electrons in hot plasmas can be detected by measuring the linear polarisation of the X-ray lines emitted from collisionally excited levels of multiply charged ions. The authors have evaluated the degree of linear polarisation of Fe24+ resonance lines and Fe23+ inner-shell excitation satellite lines observed in soft X-ray emission of solar flares and tokamaks. Collision strengths for exciting upper line magnetic sublevels were calculated using a distorted-wave method for the electron impact energy range up to 20 times the excitation threshold. It is shown how a plasma diagnostics of these non-Maxwellian electrons can be derived in a practical case.
107 citations
100 citations
TL;DR: A new application of magnetic resonance imaging to radiation dose planning is described, making use of the effect on the T1 proton relaxation times of the radiolytic Fe3+.
Abstract: Radiation dose distributions are conventionally measured using ionization chambers or diodes in liquid phantoms, or in two dimensions using film. This work describes a new application of magnetic resonance imaging to radiation dose planning. Agarose gels containing ferrous sulfate, sulfuric acid, and benzoic acid have been irradiated with /sup 137/Cs gamma rays and 6-14 MeV electrons, to doses of up to 20 Gy. The dose distributions have been imaged by magnetic resonance, making use of the effect on the T1 proton relaxation times of the radiolytic Fe/sup 3 +/. The image intensity was proportional to doses of up to 10 Gy, and images were stable for at least 24 h postirradiation. The G value for Fe/sup 3 +/ production was about 100 (molecules per 100 eV absorbed).
99 citations
87 citations
TL;DR: In this paper, the inner-shell electron decay into a Rydberg orbital at the Ar 2p to ns, nd, Kr 3d to np and Xe 4d to n p resonances was studied by three different electron measurements.
Abstract: Synchrotron radiation was used to excite an inner-shell electron into a Rydberg orbital at the Ar 2p to ns, nd, Kr 3d to np and Xe 4d to n p resonances. The resonant decay into shake-off channels was studied by three different electron measurements. Firstly, threshold electron scans were obtained over the resonances and thresholds. On the first resonance for each atom, photoelectron spectra were collected. The intensity distribution of low kinetic energy electrons was also determined for a few resonances. Finally, a shake calculation was carried out to compare with the experimental shake-off probabilities. Shake-off is observed to be a strong decay channel for these resonances.
87 citations
TL;DR: In this paper, the influence of a strong resonant driving field on the spectral properties of a single cavity-confined, two-level atom was studied under conditions of atom-cavity resonance, and the lines of the Mollow resonance fluorescence triplet were found to narrow with increasing driving field strength.
Abstract: We study the influence of a strong resonant driving field on the spectral properties of a single, cavity-confined, two-level atom Under conditions of atom-cavity resonance, the lines of the Mollow resonance fluorescence triplet are found to narrow with increasing driving field strength, indicating a dynamical decoupling of the atom from the vacuum field
TL;DR: In this article, the authors compared the results of four-wave mixing near the Na atomic resonance with a full quantum-theoretical model and showed that the results were in good agreement with the quantum model at low pump intensities and large detuning.
Abstract: Squeezed light generated by four-wave mixing near the Na atomic resonance is compared with a full quantum-theoretical model. Losses and dephasing that are due to spontaneous emission near the atomic resonance are included in this theoretical treatment. The experimental results show noise reduction greater than 1 dB below the standard quantum limits and are in good agreement with the quantum model at low pump intensities and large detuning. Theory and experiment show that limits to squeezed-light noise reduction resulting from spontaneous-emission losses can be largely avoided by using nondegenerate four-wave mixing and pump intensities near the atomic saturation values.
TL;DR: In this paper, a combined experimental/theoretical study of the coverage and frequency dependence of surface Raman scattering [S(E)RRS] of cobalt phthalocyanine (CoPc) on CaF2 roughened silver films is presented.
Abstract: We present a combined experimental/theoretical study of the coverage and frequency dependence of surface (enhanced) resonance Raman scattering [S(E)RRS] of cobalt phthalocyanine (CoPc) on CaF2 roughened silver films. The experimental spectra indicate a rather strong coverage dependence at very low coverage for excitation at or close to the molecular resonance frequency, with a peak at 0.07 monolayer (ML) followed by a rapid decrease above that. This coverage dependence differs strongly with observations on smooth films, where a much weaker dependence is observed. At very low coverage on the rough Ag films S(E)RRS enhancements comparable to SERS are observed. To model this coverage dependence, we consider the electromagnetic interactions between the adsorbate and substrate, with the substrate modeled as a metal spheroid and the adsorbate as a layer with variable coverage. Two models for this layer are considered, an effective medium model in which the layer is taken to have a coverage dependent dielectric constant, and a coupled dipole model in which both the molecules and metal are taken to be polarizable dipoles. The dependence of field enhancement and S(E)RRS intensity is studied for these two models as a function of frequency, coverage, and Stokes shift. It is found that although there are differences between the two models, the coverage dependence is similar in both, with peak intensities at about 0.1 ML for reasonably prolate spheroids. These models also demonstrate that the drop in intensity above 0.1 ML arises from damping of the plasmon resonance by the adsorbed layer. Interadsorbate interactions are found to play a role in determining the coverage dependence of the S(E)RRS intensity that is secondary to this damping. The large enhancements seen below 0.1 ML suggest that excited state quenching by the surface is not important for this nonfluorescent molecule.
TL;DR: Lineshape simulations are presented for the multiple, overlapping X-band electron paramagnetic resonance (EPR) spectra in two non-heme, high-spin iron proteins: phenylalanine hydroxylase (PAH) and diferric transferrin to determine the fraction of iron contributing to each of the sites visible by EPR.
Patent•
16 Jul 1987
TL;DR: In this article, a gas discharge lamp can be switched from its off-state to its on-state without emitting light flashes and further positively maintained the gas discharge lamps in its onstate when first ignited.
Abstract: A circuit is disclosed which is capable of positively shifting a gas discharge lamp from its off-state to its on-state without emitting light flashes and further positively maintains the gas discharge lamp in its on-state when first ignited. The circuit contains an oscillator device which generates and supplies an oscillator signal of a specific oscillator frequency from two output terminals of the oscillator device. It also contains a current limiting device an a parallel-resonance circuit comprising a capacitor and an inductor. The parallel resonance circuit has a frequency of resonance substantially identical to the oscillator frequency. The current limiting device and parallel-resonance circuit are connected in a series configuration across the output terminals of the oscillator device. Further, the gas discharge lamp is connected across or in parallel with the parallel-resonance circuit. The current limiting device preferably constitutes an inductor of a series-resonance circuit, the resonance frequency of which is lower than the oscillator frequency of the oscillator device. The oscillator device is preferably tuned to the frequency of resonance of the parallel-resonance circuit.
TL;DR: In this article, an investigation of capture of 2 keV and 24 keV neutrons in a 105 Pd target resulted in resonanceaveraged intensities of primary gamma rays with energies between 5.2 and 9.5 MeV.
TL;DR: In this article, Raman scattering measurements between 4 K and 300 K on oxidized (as grown) and reduced poly(3-methylthiophene) films were reported. And the CC bond stretching vibrational frequency was found to increase linearly from 1450 to 1470 cm −1 with incident laser energy between 1.96 and 2.81 eV possibly due to disorder.
TL;DR: In this paper, the authors analyzed the forced response of cylindrical shells in the presence of a two-to-one internal (autoparametric) resonance to a harmonic excitation having the frequency Ω.
TL;DR: The third order optical susceptibilities of trans and cis-CHs have been determined in the spectral region below the gap by measuring the third harmonic generation efficiency as discussed by the authors, and the magnitude of χ(3) parallel to the polymer chains in trans-CH x is in excess of 10 −9 esu for wavelengths larger than 1.3 μm.
TL;DR: In this paper, the lowest bending state in Ar-HCl has been completely characterized through the use of far infrared laser/microwave double resonance spectroscopy, and the value of the rotational constant is now in good agreement with that calculated by Hutson from the M5 double minimum potential surface.
Abstract: The lowest Π bending state in Ar–HCl has been more completely characterized through the use of far infrared laser/microwave double resonance spectroscopy. This extended analysis includes a partial reassignment of the far infrared spectra of Ar–H35Cl previously reported by Ray et al. and by Marshall et al., as well as an analysis of the ArH37 Cl spectra. Improved molecular constants have been determined. The value of the rotational constant is now in good agreement with that calculated by Hutson from the M5 double minimum potential surface. Along with the recently reported spectrum of the Σ bending vibration, this extended analysis provides strong evidence for the existence of two minima character in the intermolecular potential surface of Ar–HCl.
TL;DR: A review of the excitation of the spin-flip and orbital M1 resonance v the electromagnetic interaction is given in this paper, where experiments with real photons are emphasized and connections between different reactions used to study M1 transitions are discussed.
Abstract: A review of the excitation of the spin-flip and orbital M1 resonance v the electromagnetic interaction is given. Experiments with real photons are emphasized. The two different categories of M1 transitions are summarized and connections between different reactions used to study M1 transitions are discussed. Excitation of M1 resonances through photon (real and virtual) interactions at electron accelerators and with nuclear resonance fluorescence is described. (AIP)
TL;DR: In this paper, a two-dimensional, quantal study of the photodissociation of CH3O-NO within the first continuum (S0→S1, 300-400 nm) taking into account only the O−N and the N=O separations is presented.
Abstract: We report the results of a two‐dimensional, quantal study of the photodissociation of CH3O–NO within the first continuum (S0→S1, 300–400 nm) taking into account only the O–N and the N=O separations. The S1 potential energy surface is taken from recent ab initio calculations. The calculated absorption spectrum consists of two band progressions of narrow resonance lines with widths of ∼0.3 and ∼5 meV, respectively. These resonances can be associated with excitation of the O–N bond (m=0,1) and excitation of the N=O chromophore (n*=0,1,2,...). The intensities of the m=1 band are negligibly small compared to those of the m=0 band. The decay mechanism in the two cases is different: The m=0 resonances decay primarily via vibrational predissociation, i.e., a nonadiabatic transition from n* to n*−1, and yield NO products with a preferential population of the (n*−1) level. The m=1 resonances decay mainly via tunneling through a potential barrier yielding preferentially NO products in state n*. Several of the theore...
TL;DR: In this paper, the resonance Raman spectra of 13-anions in the organic superconductor P-(BEDT-TTFhI3] were studied and discussed in contrast with the nonsuperconducting phase of a-(BeddTTFHI3) at low temperature and a splitting of the Raman mode assigned to the symmetric stretching mode of the 13anions was discovered.
Abstract: The resonance Raman spectra of 13- anions in the organic superconductor P-(BEDT-TTFhI3 [BEDT-TTF represents bis(ethylenedithio)tetrathiafulvalenej were studied and discussed in com parison with the nonsuperconducting phase of a-(BEDT-TTFhI3. In both modifications at low temperature a splitting of the Raman mode assigned to the symmetric stretching mode of the 13anions was discovered. The splitting of this mode in the P-(BEDT-TTFhI3 crystals is related to the commensurate superstructure developed below 125 K in contradiction to the a phase where the splitting is related to a crystal-field effect. It is shown that an electronic excitation of the P phase crystals by laser light can induce a structural transformation at least in a thin layer of the surface. This transformation is observed by a disappearance of the splitting of the symmetric stretching mode. The structural change can be related to a transformation from the commensu rate superstructure with a superconducting transition temperature Tc = 1. 3 K into a more ordered and symmetric structure which becomes superconducting at Tc = 8. 1 K.
TL;DR: Spontaneous oxygen loss was found to degrade the sharp NMR spectrum of the Cu(1) site and Spin-lattice relaxation rates reveal strikingly different electron dynamics for the two sites.
Abstract: Nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) studies of copper nuclei are reported for high-quality single-phase powder samples of Ba/sub 2/YCu/sub 3/O/sub 7-//sub delta/. The high-field /sup 63/Cu NMR spectrum shows well-defined axial symmetry for the chain-forming Cu(1) site and evidence of appreciable disorder in the Cu(2) planes. Spontaneous oxygen loss was found to degrade the sharp NMR spectrum of the Cu(1) site. Spin-lattice relaxation rates reveal strikingly different electron dynamics for the two sites. For neither site do the rates exhibit conventional Bardeen-Cooper-Schrieffer behavior near T/sub c/.
TL;DR: The analysis of Raman excitation profiles of rotational scattering transitions is shown to be a sensitive measure of rotationally specific intramolecular dynamics in the sub-picosecond time regime as mentioned in this paper.
Abstract: The analysis of Raman excitation profiles of rotational scattering transitions is shown to be a sensitive measure of rotationally specific intramolecular dynamics in the subpicosecond time regime. O, P, Q, R, and S Raman REPs of ammonia are reported and theoretically treated using previously derived resonance rotational scattering intensity expressions. Resonance rovibrational Raman spectra are obtained with UV Raman excitation continuously resonant with the v’2 =2 vibronic band (207–210 nm) of the NH3 X → A absorption spectrum. The resulting REP analysis reveals that the rates of photodissociation on the A state surface have a significant rotational quantum dependence in the 22 band. Rovibronic lifetimes decrease from 140 to 70 fs as J increases from 2 to 8 in this resonant A state vibrational level. These lifetime effects are largely ascribed to centrifugal effects.The analysis of Raman excitation profiles of rotational scattering transitions is shown to be a sensitive measure of rotationally specific intramolecular dynamics in the subpicosecond time regime. O, P, Q, R, and S Raman REPs of ammonia are reported and theoretically treated using previously derived resonance rotational scattering intensity expressions. Resonance rovibrational Raman spectra are obtained with UV Raman excitation continuously resonant with the v’2 =2 vibronic band (207–210 nm) of the NH3 X → A absorption spectrum. The resulting REP analysis reveals that the rates of photodissociation on the A state surface have a significant rotational quantum dependence in the 22 band. Rovibronic lifetimes decrease from 140 to 70 fs as J increases from 2 to 8 in this resonant A state vibrational level. These lifetime effects are largely ascribed to centrifugal effects.
TL;DR: In this article, the low-field electron spin resonance (ESR) spectrum in the superconducting phase of YBa2Cu3O7-x was analyzed and it was shown that the individual spins responsible for superconductivity are formed and dimerized only at Tc, with their intensity sharply increasing below Tc.
Abstract: The recent discovery1–3 of high-temperature superconductivity in the Y(La}–Ba–Cu–O system has generated intense experimental and theoretical activity. On the theoretical side, it has revived the discussion of different modes of pairing in solids4,5. Here we report some important features of the low-field electron spin resonance (ESR) spectrum in the superconducting phase of YBa2Cu3O7–x, giving evidence for the dimerization of electrons on copper pairs. An intense low-field resonance appears below the critical temperature, Tc, and exhibits unresolved hyperfine structure at temperatures below 70 K. The resonance field was found to be dependent on both temperature and microwave frequency. These are well-established features characteristic of copper pairs formed due to an exchange interaction. It appears that the individual spins responsible for superconductivity are formed and dimerized only at Tc, with their intensity sharply increasing below Tc. This observation appears to be a pointer towards the possibility of the disproportionation 2Cu3+ → Cu2+ + Cu4+ in adjacent octahedra, facilitated by coupling to local eg vibrations in the superconducting phase.
TL;DR: In this article, the authors used infrared cyclotron-resonance measurements to study the dynamical conductivity of a gated GaAs two-dimensional electron gas in a perpendicular magnetic field in the regime of low carrier density and temperature.
Abstract: We use infrared cyclotron-resonance measurements to study the dynamical conductivity of a gated GaAs two-dimensional electron gas in a perpendicular magnetic field in the regime of low carrier density and temperature where electron correlation and exchange effects are most important. For $T\ensuremath{\simeq}0.4$ K the resonance narrows and shifts dramatically as the density is reduced below the point at which the lowest spin-split Landau level is filled. This observation provides the first demonstration of a strong influence of electron-electron interactions on the cyclotron-resonance line shape.
TL;DR: In this article, the weak probe-field absorption spectrum of a two level atom driven by a coherent pump field in a squeezed vacuum was calculated, where the probe field can show a linewidth smaller than the linear linwidth in normal vacuum.