Showing papers on "Resonance published in 1986"
TL;DR: For small mixing angles θ the amplification of ν oscillations in matter has the resonance form (resonance in neutrino energy or matter density) in the Sun resonance effect.
Abstract: For small mixing angles θ the amplification of ν oscillations in matter has the resonance form (resonance in neutrino energy or matter density). In the Sun resonance effect results in nontrivial changing (suppression) of ν-flux for a wide range of neutrino parameters Δm2=(3·10−4÷10−8) (eV)2, sin22θ>10−4.
912 citations
TL;DR: In this article, the authors proposed that the preferential resonances correspond to global eigenmodes of the magnetospheric cavity, and the coupling between localized field line resonance effects and the large-scale mode leads to damping of the latter.
Abstract: Many features of the magnetospheric hydromagnetic wave spectrum are fully understood, but a remaining puzzle is why selected field line resonances appear to be excited by a broadband source. In this paper, we propose that the preferential resonances correspond to global eigenmodes of the magnetospheric cavity. In order to understand the behavior of ultralow frequency waves in the terrestrial magnetosphere (geomagnetic pulsations), we describe the structure of global eigenmodes in the hydromagnetic box model of an inhomogeneous plasma. Global modes are large-scale modes whose frequencies match field line resonance frequencies somewhere in the system. The coupling between localized field line resonance effects and the large-scale mode leads to damping of the latter. In the box model the eigenmode equation yields a spectrum of discrete eigenfrequencies. For each eigenfrequency, the equation contains singular points where the field line resonance occurs. We base much of our discussion on earlier works which have used the same equation in other contexts. We describe solutions and then use the results to outline features of the modes that may be observable.
412 citations
TL;DR: Resonance Raman spectra are obtained when the wave number of the exciting radiation is close to, or coincident with, that of an electronic transition of the scattering species as mentioned in this paper.
Abstract: Resonance Raman spectra are obtained when the wave number of the exciting radiation is close to, or coincident with, that of an electronic transition of the scattering species. Such spectra are usually characterized by a very large enhancement of the intensities of particular Raman bands, sometimes with the appearance of intense overtone and combination tone progressions. The technique provides detailed information about excited electronic states because it is only the vibrational modes associated with the chromophore that are resonance-Raman active. Additionally, the high sensitivity is such that compounds at concentrations as low as 10−6 mol/L may be detected, enabling resonance Raman spectroscopy to be used as an analytical tool and for the study of chromophores in molecules of biological interest.
292 citations
221 citations
185 citations
TL;DR: In this article, a comprehensive theory of the cyclotron resonance maser (CRM) interaction in a circular waveguide is presented, and the conditions for maximum temporal and spatial growth rates are shown.
Abstract: This paper presents a comprehensive theory of the cyclotron resonance maser (CRM) interaction in a circular waveguide. The kinetic theory is used to derive the dispersion relationships for both TE and TM modes. The TE mode case has been investigated by several authors, but there has been comparatively little work on the TM mode case. However, the TM mode interaction competes effectively with the TE mode interaction at relativistic electron energies. The conditions for maximum temporal and spatial growth rates are shown. The TM mode growth rates are found to vanish when the RF wave group velocity equals the beam axial velocity (‘grazing incidence’). The single particle theory is used to derive a compact set of self-consistent non-linear equations for the TE and TM mode interactions. These equations are particularly appropriate for the cyclotron auto-resonance maser (CARM) regime but applicability extends to other regimes as well. The conditions for optimum efficiency are investigated for oscillator and amp...
178 citations
01 Dec 1986
TL;DR: In this paper, an improved method for calculating the resonance absorption heating rate is discussed and the results are compared with observations in the solar corona, and the primary conclusion to be drawn from these calculations is that to the level of the approximation adopted, the observations of the heating rate and non-thermal line broadening in the Solar corona are consistent with heating by resonance absorption mechanism.
Abstract: An improved method for calculating the resonance absorption heating rate is discussed and the results are compared with observations in the solar corona. The primary conclusion to be drawn from these calculations is that to the level of the approximation adopted, the observations of the heating rate and nonthermal line broadening in the solar corona are consistent with heating by the resonance absorption mechanism.
170 citations
TL;DR: In this article, the low-frequency shoulder of the Raman spectrum of liquid water was developed as a probe of in-phase collective motions in liquid water, and its relative intensity approached that of ice I as the supercooled liquid temperature tends toward the conjectured thermodynamic singularity in the vicinity of -46/sup 0/C.
Abstract: The low-frequency shoulder of the OH stretching Raman spectrum is developed as a probe of in-phase collective motions in liquid water. Its relative intensity approaches that of ice I as the supercooled liquid temperature tends toward the conjectured thermodynamic singularity in the vicinity of -46/sup 0/C. The collective band appears despite the large disorder of the OH stretching frequencies in the liquid compared to the strength of the resonance coupling. The resonance condition required for collective OH motions leads us to conjecture that patches of water molecules with similar hydrogen bond energies, which are capable of sustaining the resonance, appear as water is supercooled toward T/sub s/.
165 citations
TL;DR: In this article, a prototype resonator filled with argon (0.1-1.0 MPa) at 300 K was used to measure the thermodynamic temperature and the universal gas constant R with an accuracy of 0.02%.
Abstract: Gas‐filled spherical resonators are excellent tools for routine measurement of thermophysical properties. The radially symmetric gas resonances are nondegenerate and have high Q’s (typically 2000–10 000). Thus they can be used with very simple instrumentation to measure the speed of sound in a gas with an accuracy of 0.02%. We have made a detailed study of a prototype resonator filled with argon (0.1–1.0 MPa) at 300 K, with the objective of discovering those phenomena which must be understood to use gas‐filled spherical resonators to measure the thermodynamic temperature and the universal gas constant R. The resonance frequencies fN and half‐widths gN were measured for nine radially symmetric modes and nine triply‐degenerate nonradial modes with a precision near 10−7 fN. The data were used to develop and test theoretical models for this geometrically simple oscillating system. The basic model treats the following phenomena exactly for the case of a geometrically perfect sphere: (1) the thermal boundary la...
160 citations
148 citations
TL;DR: An acoustic shear wave resonator comprising a piezoelectric film having its C-axis substantially inclined from the film normal such that the shear-wave coupling coefficient significantly exceeds the longitudinal wave coupling coefficient, whereby the film is capable of resonance, and means for exciting said film to resonate as discussed by the authors.
Abstract: An acoustic shear wave resonator comprising a piezoelectric film having its C-axis substantially inclined from the film normal such that the shear wave coupling coefficient significantly exceeds the longitudinal wave coupling coefficient, whereby the film is capable of shear wave resonance, and means for exciting said film to resonate. The film is prepared by deposition in a dc planar magnetron sputtering system to which a supplemental electric field is applied. The resonator structure may also include a semiconductor material having a positive temperature coefficient of resonance such that the resonator has a temperature coefficient of resonance approaching 0 ppm/°C.
TL;DR: One method generates 1H NMR spectra of a preselected fragment of the molecule, suppressing resonances from other regions and greatly simplifying spectral appearance, not only providing valuable connectivity information but also improving sensitivity of 13C and 15N detection by up to two orders of magnitude.
Abstract: Great spectral simplification can be obtained by spreading the conventional one-dimensional nuclear magnetic resonance (NMR) spectrum in two independent frequency dimensions. This so-called two-dimensional NMR spectroscopy removes spectral overlap, facilitates spectral assignment, and provides a wealth of additional information. For example, conformational information related to interproton distances is available from resonance intensities in certain types of two-dimensional experiments. Another method generates 1H NMR spectra of a preselected fragment of the molecule, suppressing resonances from other regions and greatly simplifying spectral appearance. Two-dimensional NMR spectroscopy can also be applied to the study of 13C and 15N, not only providing valuable connectivity information but also improving sensitivity of 13C and 15N detection by up to two orders of magnitude.
TL;DR: In this article, a cylindrical dielectric-loaded resonators are analyzed and the fields within the dielectricsloaded region are postulated as the superposition of hybrid, TE, or TM modes of the infinite dielectoric-loaded waveguide, while the fields in the end regions of the resonators were described by the normal modes of a homogeneously filled waveguide.
Abstract: Analysis of cylindrical dielectric-loaded resonators is reviewed. The fields within the dielectric-loaded region are postulated as the superposition of hybrid, TE, or TM modes of the infinite dielectric-loaded waveguide, while the fields in the end regions of the resonators are described by the superposition of the normal modes of a homogeneously filled waveguide. Numerical results are presented which reveal that accurate representation of the fields in the resonant structure generally require several modes. Hence, the resonant modes cannot be correlated directly with single waveguide modes. A new method for mode identification is proposed. For a wide range of parameters, the resonant frequencies, mode charts, field expansion coefficients, field intensity, and distributions are presented. Excellent agreement of the mode charts with resonant frequency measurement results are obtained.
TL;DR: It is found that a plasmalike decomposition of the electric field into oppositely rotating components that could conceivably act to drive oppositely charged ions in the same direction through helical membrane channels is found.
Abstract: We seek to extend the recent suggestion that classical cyclotron resonance of biologically important ions is implicated in weak electromagnetic field-cell interactions. The motion of charged particles in a constant magnetic field and periodic electric field is examined under the simplifying assumption of no damping. Each of the nine terms of the relative dielectric tensor is found to have a dependence on functions that include the factor (omega 2 - omega 2B)-1, where omega B is the gyrofrequency. We also find a plasmalike decomposition of the electric field into oppositely rotating components that could conceivably act to drive oppositely charged ions in the same direction through helical membrane channels. For weak low-frequency magnetic fields, an additional feature arises, namely, periodic reinforcement of the resonance condition with intervals of the order of tens of msec for biological ions such as Li+, Na+, and K+.
01 Oct 1986-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this paper, a bunched beam of alkali ions with a pulse length of about 10 μs and an energy of 1 KeV has been retarded electrostatically and captured in flight into a Penning trap.
Abstract: A bunched beam of alkali ions with a pulse length of about 10 μs and an energy of 1 KeV has been retarded electrostatically and captured in flight into a Penning trap. A trapping efficiency of up to 70% has been determined. Subsequently the cyclotron resonance was induced. In the case of K a line width of the resonance of 4 Hz was measured at a resonance frequency of 2.3 MHz. This enables mass determinations of unstable nuclei produced at on-line mass separators with an accuracy in the sub-ppm region.
TL;DR: In this paper, the elastic constants of a trigonal crystal were determined by the RPR method up to the thirty-ninth mode using the observed and calculated resonance spectra.
TL;DR: In this paper, a two-step methodology is presented for extracting ground state population distributions and alignment factors from 1+1 resonance enhanced multiphoton ionization (REMPI) spectra.
Abstract: A two‐step methodology is presented for extracting ground state population distributions and alignment factors from 1+1 resonance enhanced multiphoton ionization (REMPI) spectra. In the first step the ion signal is corrected for variation with laser intensity as it is collected, generating an isopower spectrum. In the second step populations and alignments are derived from the isopower spectrum by correcting for the interdependent effects of saturation and intermediate state alignment. This procedure is applied to a room temperature thermal distribution of nitric oxide using the 1+1 REMPI process in which lines of the NO A 2Σ+–X 2Π (0,0) band constitute the resonant transition. The present treatment is able to recover the known rovibrational population distribution, independent of branch choice, over a wide range of practical operating conditions.
TL;DR: Hydrogen bonding in the ligand binding site of the respiratory protein hemerythrin has been investigated by resonance Raman spectroscopy and evidence for hydrogen-bond interactions between the oxo bridge of the Fe-UFe moiety and the exogenous ligand has been found for both oxyand hydroxomethemerythrin.
Abstract: Hydrogen bonding in the ligand binding site of the respiratory protein hemerythrin has been investigated by resonance Raman spectroscopy. Evidence for hydrogen-bond interactions between the oxo bridge of the Fe-UFe moiety and the exogenous ligand has been found for both oxyand hydroxomethemerythrin. In the latter case peaks are observed at 492 and 506 cm-' that shift upon '*O bridge substitution to 477 and 491 em-', respectively. These are assigned as v,(Fe-0-Fe) modes of two distinct Fe-OH conformations: the cis conformer nas an intramolecular hydrogen bond between the bound hydroxide and the oxo bridge that is lacking in the trans conformer. This proposal is supported by the observation of a temperature-dependent equilibrium between the conformers, with the cis conformer becoming more prevalent at low temperature as indicated by the increased intensity at 492 cm-I relative to 506 cm-'. The variation in the intensity as a function of temperature yields a AHo of -0.4 kcal/mol for the trans to cis conversion, consistent with the formation of a weak intramolecular hydrogen bond. The low frequency of v,(FeUFe) for cis-hydroxomethemerythrin relative to that of other methemerythrins is caused by weakening of the bridge bonds when the oxo group acts as a hydrogen-bond acceptor. A similarly low v,(Fe-0-Fe) frequency of 486 cm-' is observed for oxyhemerythrin, indicating that the bound hydroperoxide ligand also has the ability to hydrogen bond to the oxo bridge. This ;iydrogen bond is considerably stronger than that of the hydroxide adduct such that only a single v(Fe-O-Fe) peak is observed for oxyhemerythrin between 90 and 300 K. This peak undergoes a shift of +4 cm-l in D,O, an effect specific to oxyhemerythrin, owing to a weakening of the hydrogen bond upon deuterium exchange. An effect of deuterium exchange is also observed for cis-hydroxomethemerythrin, although in this case the shift is due to coupling between v,(Fe-0-Fe) and the Fe-0-D bending vibration. An additional peak located at 565 cm-' in hydroxomethemerythrin is assigned as the Fe-OH stretch on the basis of its shift to 538 cm-I in '*OH2. The relative intensity of this peak is independent of temperature, indicating that hydrogen bonding has little or no effect on the Fe-OH vibration. Hemerythrin is a nonheme iron-containing respiratory protein found in many marine invertebrates. The coelomic protein from the sipunculid Phascolopsis gouldii has an octameric quaternary structure, as does the protein from most other s0urces.I Each protein monomer contains one dioxygen binding site involving two ( I ) (a) Sanders-Loehr, J.; Loehr, T. M. Adu. Inorg. Biochem. 1979, I , 235-252. (b) Klotz, I. M.; Kurtz, D. M., Jr. Acc. Chem. Res. 1984. 17, 16-22. (c) Wilkins, R. G.; Harrington, P. C . Ado. Znorg. Biochem. 1983, 5 , 52-85. (d) Sanders-Loehr, J. In Frontiers in Bioinorgunic Chemistry; Xavier, A. V. . Ed.; VCH Publishers: Weinheim, 1986; pp 574-583. iron atoms that, in the deoxy form of hemerythrin, are in the ferrous state.'q2 After the dioxygen is bound, the iron atoms are oxidized to the ferric state with concomitant reduction of O2 to peroxide, resulting in the formation of ~xyhemerythr in .~-~ An (2) Sanders-Loehr, J.; Loehr, T. M.; Mauk, A. G.; Gray, H. B. J. Am. ( 3 ) Garbett, K.; Darnall, D. W.; Klotz. I. M.; Williams, R. J. P. Arch. (4) Dum, J . B. R.; Shriver. D. F.: Klotz, I. M. f r o r . Natl. Arad. Sci. Chem. Sor. 1980, 102, 6992-6996. Binchem. Biophys. 1969, 135, 419-434. W.S.A. 1973, 70, 2582-2584. 0002-7863/86/ 1508-2437$01.50/0
TL;DR: In this article, the frequency limit of negative differential resistance (NDR) devices employing resonant tunneling in double barrier quantum well structures is analyzed, and it is shown that the standard theoretical approach to Resonant Tunneling together with a unitarity bound leads to a lower bound on NDR which is in turn related to the maximum oscillator frequency.
Abstract: The frequency limit of negative differential resistance (NDR) devices employing resonant tunneling in double barrier quantum well structures is analyzed. We show that the standard theoretical approach to resonant tunneling together with a unitarity bound leads to a lower bound on NDR which is in turn related to the maximum oscillator frequency. The bound on NDR can be achieved in devices with narrow width resonances. However, too narrow a width can cause Wigner–Eisenbud resonance time delay. These considerations indicate that devices of the type studied by T. C. L. G. Sollner, P. E. Tannenwald, D. D. Peck, and W. D. Goodhue [Appl. Phys. Lett. 45, 1319 (1984)] could oscillate up to roughly 1 THz.
TL;DR: In this article, a pseudostate close-coupling method has been used to examine the scattering in the non-resonant and resonant regions of an ion, which is performed using an algebraic variational method.
Abstract: The scattering of electrons by ${\mathrm{He}}^{+}$ ions has been studied below the N=2 threshold of the ion. A pseudostate close-coupling method has been used to examine the scattering in the nonresonant and resonant regions. The calculations are performed using an algebraic variational method. Extensive pseudostate basis sets of differing characters are employed. In the nonresonant region, short-range electron-electron correlations are emphasized. In the vicinity of the resonances, the dominant projectile-target electron correlations are comparatively long range. S-, P-, and D-wave phase shifts of high accuracy are obtained for both the singlet and the triplet spin states. The present phase shifts agree very well with those obtained by Shimamura by a variational procedure for the S wave and with those of McGreevy and Stewart by a many-body perturbation method for the singlet P wave. The present phase shifts are in disagreement with the polarized orbital results of Khan et al. Resonance parameters are calculated for 15 S-wave resonances, 16 P-wave resonances, and 19 D-wave resonances with the outer electron extending up to n\ensuremath{\simeq}8. Estimates of quantum defects and the reduced widths are obtained for various Rydberg series of the doubly excited states. A number of the high-lying resonances are predicted for the first time. The agreement of the present energy values and the auotionization widths with the available experimental values is excellent.
TL;DR: Certain applications of chemical shift imaging, such as in the determination of fatty liver disease, have greater diagnostic utility than conventional magnetic resonance imaging, and edge artifacts caused by chemical shift effects can be eliminated by certain selective methods of data acquisition employed inchemical shift imaging.
Abstract: Chemical shift is the phenomenon that is seen when an isotope possessing a nuclear magnetic dipole moment resonates at a spectrum of resonance frequencies in a given magnetic field. These resonance frequencies, or chemical shifts, depend on the chemical environments of particular nuclei. Mapping the spatial distribution of nuclei associated with a particular chemical shift (e.g., hydrogen nuclei associated with water molecules or with lipid groups) is called chemical shift imaging. Several techniques of proton chemical shift imaging that have been applied in vivo are presented, and their clinical findings are reported and summarized. Acquiring high-resolution spectra for large numbers of volume elements in two or three dimensions may be prohibitive because of time constraints, but other methods of imaging lipid of water distributions (i.e., selective excitation, selective saturation, or variations in conventional magnetic resonance imaging pulse sequences) can provide chemical shift information. These techniques require less time, but they lack spectral information. Since fat deposition seen by chemical shift imaging may not be demonstrated by conventional magnetic resonance imaging, certain applications of chemical shift imaging, such as in the determination of fatty liver disease, have greater diagnostic utility than conventional magnetic resonance imaging. Furthermore, edge artifacts caused by chemical shift effects can be eliminated by certain selective methods of data acquisition employed in chemical shift imaging.
TL;DR: In this paper, the pattern of solar magnetic fields in spherical harmonics for a data set of 25 years and power spectrum analysis of the harmonic coefficients reveals a strikingly resonant modal structure.
Abstract: Decomposition of the pattern of solar magnetic fields in spherical harmonics for a data set of 25 years and power spectrum analysis of the harmonic coefficients reveals a strikingly resonant modal structure. The resonance frequencies contain information on the structure of the magnetic fields in the Sun's interior.
TL;DR: It is shown that the cell surface charge shifts the resonance frequency and influences the absolute value of rotation velocity.
TL;DR: The pattern of multiple-quantum excitation and response, influenced largely by the concerted interactions of groups of coupled nuclei, simplifies the NMR spectrum in some instances and provides significant new information in others.
Abstract: A nuclear magnetic resonance (NMR) event is popularly viewed as the flip of a single spin in a magnetc field, stimulated by the absorption or emission of only one quantum of radio-frequency energy. Nevertheless, resonances between nuclear spin states that differ by more than one unit in the Zeeman quantum number also can be induced in systems of coupled spins by suitably designed sequences of radio-frequency pulses. Pairs of states excited in this way oscillate coherently at the frequencies of the corresponding multiple-quantum transitions and produce a response that may be monitored indirectly in a two-dimensional time-domain experiment. The pattern of multiple-quantum excitation and response, influenced largely by the concerted interactions of groups of coupled nuclei, simplifies the NMR spectrum in some instances and provides significant new information in others. Applications of multiple-quantum NMR extend to problems in many different areas, ranging from studies of the structure and function of proteins and nucleic acids in solution to investigations of the arrangements of atoms in amorphous semiconductors. The specific spectroscopic techniques are varied as well and include methods designed, for example, to simplify spectral analysis for liquids and liquid crystals, eliminate inhomogeneous broadening, study interatomic connectivity in liquid-state molecules, identify clusters of atoms in solids, enhance the spatial resolution in solid-state imaging experiments, and probe correlated molecular motions.
TL;DR: In this paper, the frequency dependence and amplitude of the rotational spectral density function, J(omega), was determined for sucrose solutions in D/sub 2/O NMR spinlattice relaxation times and nuclear Overhauser enhancements.
Abstract: /sup 13/C NMR spin-lattice relaxation times and nuclear Overhauser enhancements were measured as a function of concentration, temperature, and magnetic field strength for sucrose solutions in D/sub 2/O. These data were used to determine the frequency dependence and amplitude of the rotational spectral density function, J(omega). The authors find that J(omega) has the same frequency dependence as the theoretical spectral density function for a rigid molecule, but it has a lower amplitude. At the average ring-carbon atom in sucrose, the low-frequency amplitude of J(omega) is about 89% of the theoretical rigid-molecule value. Presumably, the amplitude is lowered by rotational components of vibrational motions, which rapidly accomplish part of the averaging that otherwise would be performed by the slower molecular rotations of a rigid molecule. The results also reveal small differences in the amplitudes of J(omega) at different sucrose ring positions; these differences can be used to measure the relative amplitudes of local torsional and vibrational motions.
TL;DR: In this paper, the optical line shape of the intense π-π* ‘Soret’ transition of ferrocytochrome c as a function of temperature was studied using a multimode time correlator model.
Abstract: We have studied the optical line shape of the intense π–π* ‘‘Soret’’ transition of ferrocytochrome‐c as a function of temperature. Use of the linear electron–nuclear coupling strengths found from the transform analysis of the resonance Raman excitation profiles allows us to simulate the measured line shape changes using a multimode time correlator model that is exact at all temperatures. Four major sources of line broadening are considered: (1) Multimode broadening due to the observed Raman (Franck–Condon) active modes; (2) broadening due to a low frequency Franck–Condon active bath that is not observed directly in the resonance Raman spectrum; (3) inhomogeneous broadening, σ, modeled as a Gaussian distribution of 0–0 transition frequencies; (4) homogeneous broadening, Γ, due to exponential population decay of the excited electronic state. We find conclusive evidence that mechanism (2) is not important in determining the Soret band line shape and that mechanism (3) is constrained to an upper limit of σmax...
TL;DR: In this paper, the position of π and σ resonances in the C K edge spectra were determined for multilayer and submonolayer coverages of C2H2.