Showing papers on "Resonance published in 1976"
457 citations
TL;DR: In this article, a theory was developed on the free vibration of a crystal of rectangular parallelepiped and of general symmetry by extending Demarest's theory of cube resonance, which is applied to determine elastic constants of crystals from the resonance frequencies of its free vibrations.
Abstract: A theory was developed on the free vibration of a crystal of rectangular parallelepiped and of general symmetry by extending Demarest's theory of cube resonance. All vibrational modes were classified and described in detail for the case of orthorhombic symmetry. The theory is applied to determine elastic constants of crystals from the resonance frequencies of its free vibrations. The method of numerical analysis of resonance frequency data was studied to derive a practical way of elastic constant determination. As an example, the elastic constants of two specimens of single crystal olivine (Mg1.8Fe0.2SiO4) were determined. The applicability of the resonance method is largely extended by the present theory to the precise determination of elastic constants of single crystals.
395 citations
TL;DR: A theoretical dependence of the resonance frequency shift of the main component and frequency splitting of two components active in the infrared spectra on the number of polypeptide chains in the finite sheet has been found.
Abstract: Theoretical treatment of resonance interaction of amide-I vibration has been done in a dipole–dipole approximation on the basis of perturbation theory. A single infinite antiparallel-chain pleated sheet as well as different kinds of its finite fragments have been considered. A good agreement has been obtained between calculated spectral parameters of amide I of the infinite sheet and observed ones in infrared and Raman spectra of synthetic polypeptides and fibrous proteins. A theoretical dependence of the resonance frequency shift of the main component and frequency splitting of two components active in the infrared spectra on the number of polypeptide chains in the finite sheet has been found.
319 citations
TL;DR: In this paper, a complete and detailed treatment of a three-level atom interacting with two near-resonant monochromatic fields is presented, assuming that the only damping mechanism is radiative damping, and that the atoms all have the same resonance frequencies.
Abstract: A complete and detailed treatment of a three-level atom interacting with two near-resonant monochromatic fields is presented. It is assumed that the only damping mechanism is radiative damping, and that the atoms all have the same resonance frequencies, as is the case in an atomic beam. Detailed analytic solutions as well as numerical examples are determined from quantum-electrodynamic equations of motion. In addition, approximation techniques are presented which allow one to get accurate quantitative predictions for strong applied fields from simple rate-equation-like arguments. Absorption and emission spectra are determined, as are the transient and steady-state response of the atom. Two of the more interesting predictions are an emission spectrum containing up to seven components and a prediction of steady-state populations larger than 0.5 in the second excited state.
313 citations
280 citations
TL;DR: In this article, a cross-beam method was used to study vibrational excitation of HF and HCl by electron impact at very low collision energies, and the absolute cross sections reached values of 10-15 cm2 for the threshold peaks in the nu = 1 channel.
Abstract: Differential scattering experiments with the crossed-beam method have been performed to study vibrational excitation of HF and HCl by electron impact at very low collision energies. The excitation functions for nu =1 and nu =2 have been measured from threshold to some eV above. In each case, an unusually strong and sharp threshold peak is observed with a broad resonance region following thereafter. The absolute cross sections reach values of the order of 10-15 cm2 for the threshold peaks in the nu =1 channel. The angular distributions are isotropic in the whole resonance region. The threshold resonances are interpreted as quasi-bound 2 Sigma + states in the dipole field possibly correlated with H*+X-. The broad resonance region is attributed to a very short-lived resonance state which may be the HX- 2 Sigma + state correlated with ground-state fragments H+X-.
216 citations
TL;DR: In this paper, it was shown that the well known resonance properties of the "heavy nucleus plus slow neutron" system make it a sensitive receiver, sharply tuned to the current values of nuclear constants.
Abstract: THE possibility that fundamental nuclear constants may vary slowly while the Universe expands has been discussed by several authors1–5. I try here to show that the well known resonance properties of the ‘heavy nucleus plus slow neutron’ system make it a sensitive ‘receiver’, sharply tuned to the current values of nuclear constants.
198 citations
TL;DR: In this paper, it was shown that the energy of the monopole resonance is proportional to the square root of the compression modulus of finite nuclei K A, which is a regular function of K ∞ and is a possible way of reaching the compressibility of nuclear matter.
189 citations
TL;DR: A detailed account of the techniques used to generate these resonance configurations from the purely nucleonic configurations is given in this paper, where two-and three-nucleon systems in which the resonance configurations appear to play a role are discussed.
Abstract: The present status of the theory of nucleon resonances in nuclei is reviewed. A detailed account is given of the techniques used to generate these resonance configurations from the purely nucleonic configurations. Situations in two- and three-nucleon systems in which the resonance configurations appear to play a role are discussed. Heavier nuclei are also mentioned. The effect of resonances in nuclear and neutron matter is also reviewed.
183 citations
TL;DR: Solid state nuclear magnetic resonance as a method of determining crystal structure has had limited success, but can be mitigated by a family of coherent averaging techniques in double resonance, with considerably improved prospects for locating the rare spins with respect to their nearby neighbors.
Abstract: Solid state nuclear magnetic resonance as a method of determining crystal structure has had limited success. Three distinct reasons for this failure can be identified when the resonance spectrum is of a dilute spin species in the presence of another abundant species. Two of these difficulties, and in part the third, can be mitigated by a family of coherent averaging techniques in double resonance, with considerably improved prospects for locating the rare spins with respect to their nearby neighbors. A particularly advantageous procedure is described and possible applications are discussed.
TL;DR: A theory for predicting the effective sample composition in the illuminated volume as a function of the flow rate, light intensity, and spectral characteristics of the photolabile species is presented.
Abstract: We have devised a method for obtaining the resonance Raman spectrum of a photolabile molecule before it is modified by light. The essence of this technique is that the sample is flowed through the light beam at a sufficiently high velocity so that the fraction of photoisomerized (or photodestroyed) molecules in the illuminated volume is very low. This rapid-flow technique has enabled us to measure the resonance Raman spectrum of unphotolyzed bovine rhodopsin in Ammonyx LO detergent solution and in sonicated retinal disc membranes. The major features of these spectra, which are very similar to one another, are the protonated Schiff base line near 1660 cm-1, the ethylenic line at 1545 cm-1, lines due to skeletal modes at 1216, 1240, and 1270 cm-1, and a line due to C-H bending at 971 cm-1. The resonance Raman spectrum of unphotolyzed isorhodopsin formed by the addition of 9-cis-retinal to opsin was also measured. The spectrum of isorhodopsin is more complex and differs markedly from that of rhodopsin. In isorhodopsin, the ethylenic line is shifted to 1550 cm-1, and there are six lines between 1153 and 1318 cm-1. The rapid-flow technique described here makes it feasible to control the extent of interaction between light and any photolabile molecule. We present a theory for predicting the effective sample composition in the illuminated volume as a function of the flow rate, light intensity, and spectral characteristics of the photolabile species.
Book•
01 Jan 1976TL;DR: In this paper, an ESR spectrometer for recording ESR signals with submicrosecond response time (RC=0.3 μsec) is described, which can be observed to within less than 1 μsec of the radiolysis pulse used to produce the radicals.
Abstract: An ESR spectrometer for recording ESR signals with submicrosecond response time (RC=0.3 μsec) is described. Signals can be observed to within less than 1 μsec of the radiolysis pulse used to produce the radicals. The transient signals are observed directly in absorption for ease of analysis of their time dependence. Two modes of operation are possible: display of a spectrum at a fixed time after the pulse and the time profile at a fixed magnetic field. The latter mode (which was mainly used in this work) makes use of 100 data points in time, taken sequentially and averaged in a minicomputer. The magnetic field is computer controlled and is adjusted for changes in microwave frequency to maintain resonance. Analysis of the time‐dependent signals was by means of the Bloch equations so modified as to take account of changes in radical concentration with time, any initial magnetization upon radical formation, and CIDEP effects produced during radical decay. The ESR signal of the hydrated electron was observed ...
TL;DR: In this article, a measurement of complex elastic constants was made on two single crystal MgO specimens using a resonance method and the results on the real part of the elastic constants are consistent with those reported by CHANG and BARSCH (1969) and SPETZLER (1970) except for a small difference in C12.
Abstract: A measurement of complex elastic constants is made on two single crystal MgO specimens using a resonance method. The results on the real part of the elastic constants are consistent with those reported by CHANG and BARSCH (1969) and SPETZLER (1970) except for a small difference in C12. The elastic constants at a theoretical density of 3.584g/cm3 are C11= 2.978±0.004, C12=0.970±0.005, C44=1.563±0.002, Cs=(C11-C12)/2= 1.004±0.001, and K=(C11+2·C12)/3=1.639±0.006 in Mbar at 293K. The small deviations of the elastic constants in different specimens from the above valucs are well related to the deviation of the actual density from the theoretical one. The internal frictions relating to respective elastic constants are Q-111=0.23±0.61, Q-112=-0.35±1.79, Q-144=1.87±0.16, and Q-1s=0.51±0.14 in units of 10-4 at room temperature and 1MHz. The dominant dis-sipation is not caused by the shear on a plane of easy glide {110} , but the shear on {100}.
TL;DR: In the examination of intact muscles by 31P nuclear magnetic resonance spectroscopy, a number of signals have been detected in the phosphodiester region of the spectrum which could not be correlated with the known common phosphates of muscle tissue.
Abstract: In the examination of intact muscles by 31P nuclear magnetic resonance spectroscopy, a number of signals have been detected in the phosphodiester region (-0.5 to 0.5 ppm) of the spectrum which could not be correlated with the known common phosphates of muscle tissue. These signals arise from perchloric acid extractable compounds with several common chemical properties, one of which is a ready solubility in nearly anhydrous ethanol solutions. A component contributing to the major resonance has been identified as glycerol-3-phosphorylcholine. This characterization is based on both 31P nuclear magnetic resonance and chromatographic data.
TL;DR: In this paper, the dynamics of intramolecular vibrational energy transfer is studied, with particular reference to its effect on the unimolecular dissociation rates of isolated molecules, represented as a set of classical, coupled, nonlinear (anharmonic) oscillators which transfer energy through resonant interactions.
Abstract: The dynamics of intramolecular vibrational energy transfer is studied, with particular reference to its effect on the unimolecular dissociation rates of isolated molecules. The molecule is represented as a set of classical, coupled, nonlinear (anharmonic) oscillators which transfer energy through resonant interactions. We suggest that isolated nonlinear resonances (which predominate at low energies) lead to trapping of the vibrational energy of the system, hence to slow vibrational relaxation, while resonance overlap at higher energies leads to rapid energy exchange and the random lifetime distribution assumed by RRKM theory. Results are presented for some simple model systems, and the approach is compared with other recent theoretical descriptions of vibrational relaxation in isolated molecules.
TL;DR: In this paper, the cyclotron resonance of electrons and of holes in Cu2O has been observed between 1.2 and 20K using frequencies of 34 and 137 GHz, and the authors attribute the electron resonance to the lowest Gamma 1+( Gamma 6+) minimum of the conduction band and the heavier hole to the uppermost Gamma 7+ hole band.
Abstract: The cyclotron resonance of electrons and of holes in Cu2O has been observed between 1.2 and 20K using frequencies of 34 and 137 GHz. Electrons have an isotropic polaron mass of (0.99+or-0.03)m0 where m0 is the mass of the free electron. Holes have isotropic polaron masses of (0.58+or-0.03)m0 and (0.69+or-0.04)m0, the error bars defining the points of half-height on the observed resonance curves. The authors attribute the electron resonance to the lowest Gamma 1+( Gamma 6+) minimum of the conduction band and the heavier hole to the uppermost Gamma 7+ hole band. The lighter hole is attributed tentatively to the Gamma 8+ maximum of the hole band. The exciton spectra of Cu2O are discussed in terms of these masses.
TL;DR: In this article, the rotational transfer rates and the temporal behavior of the population distribution over rotational levels after the population was placed in a single level were investigated and compared with a rate equation model and rate constants for individual relaxation steps were obtained.
Abstract: Rotational relaxation effects in HF were observed with double resonance ir experiments. Two single wavelength lasers were employed: a pulsed laser was used to pump a population to a particular vibrational–rotational level, and a stable cw laser was used as an absorption probe to determine the loss or arrival of population in specific J levels. Results are described for both the rotational transfer rates and the temporal behavior of the population distribution over rotational levels after the population was placed in a single level. Rotational transfer rates were found to be three orders of magnitude faster than V–T relaxation and to vary with ΔJ. The data for rotational relaxation were compared with a rate equation model and rate constants for individual relaxation steps were obtained.
TL;DR: In this paper, differential and integral cross sections for the excitation of the (100, 001) and (010) modes are given in absolute units, and two distinct resonance regions are observed: strong and sharp threshold resonances and a broad resonance region centred around 6-8 eV.
Abstract: For pt.I see ibid., vol.9, no.14, p.2521 (1976). Differential scattering experiments with the crossed-beam method have been performed to study vibrational excitation of H2O by electron impact for collision energies from threshold to 10 eV. Differential and integral cross sections for the excitation of the (100, 001) and 010 modes are given in absolute units. Two distinct resonance regions are observed which are superimposed on a background of direct excitation: strong and sharp threshold resonances and a broad resonance region centred around 6-8 eV. The broad enhancement of the cross sections around 6 eV is attributed to a very short-lived 2A1 state of H2O-. The threshold resonances are interpreted as quasi-bound states in the dipole field of H2O. They are expected to be of general importance in electron-polar-molecule interactions.
TL;DR: In this article, the high-frequency magnetoconductivity of the quasi-two-dimensional electron gas in a surface space-charge layer on Si has been investigated using a far-infrared laser transmission spectrometer.
Abstract: We study the high-frequency magnetoconductivity of the quasi-two-dimensional electron gas in a surface space-charge layer on Si. The experiments are carried out at low temperatures and in high magnetic field, using a far-infrared laser transmission spectrometer. Surface cyclotron resonance of electrons in inversion and accumulation layers on the (100) surface of Si has been investigated. The two dimensionality of the electron system is demonstrated by experiments in magnetic fields tilted with respect to the surface normal. Quantum oscillations are observed in the resonance amplitude, and are explained by a recent theory of Ando and Uemura. The resonance line shape is compared with the theoretical predictions. Scattering times, as extracted from the line shape, are related to those obtained from low-frequency conductivity experiments. The influence of a substrate bias voltage on the resonance is investigated. Subharmonic structure of the cyclotron resonance and its dependence on the surface charge density ${n}_{s}$ are explored in the experiments. From the position of the fundamental resonance the cyclotron effective mass ${m}_{c}^{*}$ is obtained. For ${n}_{s}\ensuremath{\gtrsim}1\ifmmode\times\else\texttimes\fi{}{10}^{12}$ ${\mathrm{cm}}^{\ensuremath{-}2}$ and temperatures in the liquid-helium range we find ${m}_{c}^{*}=(0.197\ifmmode\pm\else\textpm\fi{}0.005){m}_{0}$ independent of ${n}_{s}$. For ${n}_{s}l1\ifmmode\times\else\texttimes\fi{}{10}^{12}$ ${\mathrm{cm}}^{\ensuremath{-}2}$ a marked increase of ${m}_{c}^{*}$ with decreasing ${n}_{s}$ is observed. In some samples, and at ${n}_{s}\ensuremath{\lesssim}0.5\ifmmode\times\else\texttimes\fi{}{10}^{12}$ ${\mathrm{cm}}^{\ensuremath{-}2}$, a sample- and ${n}_{s}$-dependent decrease of the resonance field is found and interpreted as resulting from effects of localization. Results for electrons on (110) and (111) surfaces are also presented. The effect of multiple reflections in the semiconductor substrate on the transmission line shape of the surface cyclotron resonance is discussed.
TL;DR: In this paper, a double resonance multiple pulse nuclear magnetic resonance experiment is proposed and demonstrated which allows the use of heteronuclear dipolar interactions to determine geometrical, orientational, and motional information in polycrystalline solids.
Abstract: A double resonance multiple pulse nuclear magnetic resonance experiment is proposed and demonstrated which allows the use of heteronuclear dipolar interactions to determine geometrical, orientational, and motional information in polycrystalline solids. 13C–1H double resonance experiments are performed in polycrystalline benzene and calcium formate to demonstrate the capabilities of the technique in its present form.
TL;DR: In this article, a method for simultaneous cooling and trapping of atoms and molecules in a low-pressure gas under forces caused by recoil during spontaneous or induced transitions of the particles in the resonance field of a three-dimensional standing light wave is proposed.
TL;DR: In this article, a single coil double resonance probe was proposed to tune NMR probe circuits and matching impedances using a variable length transmission line as one of the tuning elements, which is useful for high voltage circuits where suitable tuning elements may not be placed adjacent to the rf field-producing coil.
Abstract: First we discuss a method of tuning NMR probe circuits and matching impedances which employs a variable length transmission line as one of the tuning elements. This method is useful for high voltage circuits where, due to space considerations, suitable tuning elements may not be placed adjacent to the rf field‐producing coil. Second, we describe the design of a single coil double resonance probe which uses λ/4 transmission lines as filters as well as tuning elements. This double resonance probe is useful when the two frequencies of interest are widely separated.
15 Feb 1976
TL;DR: In this article, the infrared emission of CO trapped in solid Ne and Ar is observed at low temperature and the first vibrational level of 12 C 16 O is excited by a Q -switched frequency doubled CO 2 laser.
Abstract: The infrared emission of CO trapped in solid Ne and Ar is observed at low temperature. The first vibrational level of 12 C 16 O is excited by a Q -switched frequency doubled CO 2 laser. The emission spectrum consists of several lines arising from upper vibrational levels of 12 C 16 O and also of 13 C 16 O and 12 C 18 O which are present in natural abundance. An interpretation is proposed which is based on the assumption that long range dipole—dipole interaction is the main physical process involved in these experiments. Resonance energy transfer produces an energy migration among 12 C 16 O molecules without any change in vibrational populations. Phonon assisted energy transfer takes place between vibrational levels of the various isotopic species present in the solution. In order to satisfy the resonance condition a phonon is emitted or absorbed whose energy compensates for the energy mismatch between the transitions in each interacting molecule due to isotopic effect and or vibrational anharmonicity. The range of this process is greatly extended by energy migration. At the low phonon bath temperature phonon emission is much more probable than phonon absorption. So a strong excitation of upper vibrational levels with in some cases population inversions is observed. Molecular impurities act as efficient quenching centers even at very low concentration. When highly purified samples are used, the fluorescence decay time is found to be 20.6 ms in Ne and 14.5 ms in Ar and does not significantly depend upon concentration and temperature. It is concluded that radiationless relaxation is unimportant.
TL;DR: In this paper, the authors measured the multiphoton ionization spectrum of trans-1,3-butadiene from dye laser wavelengths of 365 to 468 nm using an intensity-corrected system.
Abstract: The multiphoton ionization spectrum of trans‐1,3‐butadiene has been measured from dye laser wavelengths of 365 to 468 nm using an intensity‐corrected system. In the four‐photon ionization region to lower energy than 405 nm, many three‐photon resonances with Rydberg states are seen and a new series with a quantum defect of 0.04 is identified. The symmetries of the observed Rydberg series are discussed. Above 405 nm in energy, a resonance occurs with the ? state seen in one‐photon absorption spectra, only the structure in the multiphoton ionization spectrum is characteristic of an allowed two‐photon resonance. From the vibronic structure of this state, it is argued that it has symmetry 1Bg. In the region covered by this study (42 700 to 54 800 cm−1 in two‐photon energy) no state was found to which a 1Ag symmetry designation could be applied.