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Showing papers on "Energy (signal processing) published in 1974"


Journal ArticleDOI
TL;DR: In this paper, a very sharp peak was observed in the cross section of the Hadron at a center-of-mass energy of 3105 ± 3.3 GeV.
Abstract: We have observed a very sharp peak in the cross section for ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\mathrm{hadrons}, {e}^{+}{e}^{\ensuremath{-}}$, and possibly ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ at a center-of-mass energy of 3105\ifmmode\pm\else\textpm\fi{}0003 GeV The upper limit to the full width at half-maximum is 13 MeV

1,008 citations


Journal ArticleDOI
TL;DR: In this article, the results of PLE measurements are combined with data on reflection and luminescence in the intrinsic region to determine the positions of $A, $B, and $C$-exciton ground-state transition energies and the lowest band gap.
Abstract: In the absence of samples suitable for transmission measurements, photoluminescence excitation spectra (PLE) have been found useful in the evaluation of detailed information about the lowest direct-absorption edge of GaN. In this work the results of PLE measurements are combined with data on reflection and luminescence in the intrinsic region to determine the positions of $A\ensuremath{-}$, $B\ensuremath{-}$, and $C$-exciton ground-state transition energies and the lowest band gap. Neglecting polariton effects, the value of the $A$-exciton ground-state transition energy is determined as being ${E}_{A}^{x}=3.4751\ifmmode\pm\else\textpm\fi{}0.0005$ eV at 1.6 K from combined PLE and emission spectra. The corresponding values for $B$ and $C$ exciton transitions are found to be ${E}_{B}^{x}=3.4815\ifmmode\pm\else\textpm\fi{}0.001$ eV and ${E}_{C}^{x}=3.493\ifmmode\pm\else\textpm\fi{}0.005$ eV from PLE spectra. The lowest band gap is determined to be ${E}_{g}^{A}={3.503}_{\ensuremath{-}0.002}^{+0.005}$ eV at 1.6 K, which fixes the ground-state $A$-exciton binding energy as ${E}_{B}(A)={28}_{\ensuremath{-}3}^{+6}$ meV, in good agreement with the effective-mass value. The temperature dependence of the band gap could also be accurately measured in PLE spectra and can be described by an expression ${E}_{g}^{A}=[3.503+\frac{(5.08\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}{T}^{2})}{(T\ensuremath{-}996)}]$ eV for $Tl295$ K, with an estimated relative uncertainty of \ifmmode\pm\else\textpm\fi{} 0.002 eV.

696 citations


Journal ArticleDOI
TL;DR: An analysis technique for biological shape based on the concept of bending energy provides several new results concerning image processing including a sampling theorem for simply connected closed contours and a fast algorithm for calculation of the bending energy.
Abstract: An analysis technique for biological shape based on the concept of bending energy has been developed. The technique permits the calculation of the amount of energy (work) that would have to be expended to form typical biological shapes out of a linear, thin-shelled medium. In addition the development of this analysis procedure provides several new results concerning image processing including a sampling theorem for simply connected closed contours and a fast algorithm for calculation of the bending energy.

244 citations


Journal ArticleDOI
TL;DR: In this article, a second sharp peak was observed in the cross section of the Hadron at a center-of-mass energy of 3695 GeV at half-maximum.
Abstract: We have observed a second sharp peak in the cross section for ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\mathrm{hadrons}$ at a center-of-mass energy of 3695\ifmmode\pm\else\textpm\fi{}0004 GeV The upper limit of the full width at half-maximum is 27 MeV

216 citations


Patent
16 Sep 1974
TL;DR: In this paper, a receiving coil is inductively coupled to the radiation over a given distance substantially less than a wave length of the high frequency signal to provide a received signal without the necessity of any electrical wires.
Abstract: A normal 117-volt, 60 cycle source is converted into a high frequency signal resulting in radiation of a substantial portion of the energy in the signal. A receiving coil is inductively coupled to the radiation over a given distance substantially less than a wave length of the high frequency signal to provide a received signal without the necessity of any electrical wires. The received signal in turn is converted into a D.C. signal and passed to a rechargeable battery for charging. The inductive coupling can be utilized for recharging portable electrical instruments having rechargeable batteries or for charging larger rechargeable batteries such as used in electrically driven vehicles.

207 citations


Journal ArticleDOI
TL;DR: In this paper, the bond-orbital model is reformulated taking explicit account of the large overlap of two hybrids in the same bond rather than absorbing it in a pseudopotential.
Abstract: The bond-orbital model is reformulated taking explicit account of the large overlap of two hybrids in the same bond rather than absorbing it in a pseudopotential. This gives a correction to the cohesive energy but other changes are absorbed in the ${V}_{1}$, ${V}_{2}$, and ${V}_{3}$ for each material. These parameters are reevaluated taking band calculations as the standard for ${V}_{1}$ (but using the atomic term values to scale from material to material) and taking the energy of the optical-absorption peak as the standard for ${V}_{2}$ and ${V}_{3}$ (but using the dielectric constant to scale from material to material). Using the new parameters we test the model by comparison of predictions with experiment (or accurate calculations) for various valence-band gaps, the pressure dependence of the dielectric constant, the macroscopic transverse charge, the piezoelectric constant, the photoelectric threshold, and the cohesive energy. Discrepancies in the cohesive energy are found to scale with a reasonable form for the interbond correlation energy, giving a semiempirical expression for the cohesive energy in terms of parameters of the bond-orbital model. The covalent energy is found in this study to scale with a kinetic energy (with the inverse square of the bond length) both under pressure and for variation from material to material.

160 citations


Journal ArticleDOI
P. M. Platzman1, H. Fukuyama1
TL;DR: In this paper, the phase diagram of a two-dimensional electron liquid immersed in a uniform background of charge is analyzed, and a qualitative argument based on energy considerations alone yields the shape of the liquid-solid boundary.
Abstract: The phase diagram of a two-dimensional electron liquid immersed in a uniform background of charge is analyzed. We present a qualitative argument based on energy considerations alone which yields the shape of the liquid-solid boundary. To determine absolute values of the density and temperature we utilize a microscopoic theory based on the self-consistent harmonic approximation to the phonon spectrum of a solid. This theory is a one-phase instability theory of the long-wavelength transverse mode in the solid phase alone. It yields values of ${r}_{s}\ensuremath{\approx}5$ in the quantum regime and ${\ensuremath{\Gamma}}_{0}=3$ in the classical case.

119 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that tunneling can be thought of in terms of a slight generalization of the coherence effects which dominate the other kinds of experiments, and a relation is discussed between tunneling and other experiments such as far-infrared absorption and acoustic attenuation in superconductors.
Abstract: To second order in perturbation theory the tunneling current between two superconductors can be expressed as follows: $I(V,T)={I}_{J1}(V,T)sin\ensuremath{\phi}+{I}_{J2}(V,T)cos\ensuremath{\phi}+{I}_{\mathrm{qp}}(V,T),$ where $V$ is a constant voltage across the tunneling barrier, $T$ is the temperature, and $\ensuremath{\phi}=\ensuremath{-}\frac{2eVt}{\ensuremath{\hbar}}+{\ensuremath{\phi}}_{0}$ is the difference in the phases of the wave functions of the superconductors on each side of the barrier. Numerical evaluations of each of the terms are presented as functions of voltage for several temperatures. For the second term we find a different sign from that found in previous numerical work. When the superconductors on each side of the tunneling barrier are different, structure occurs at a voltage corresponding to the difference in the energy gaps. For the first two terms this structure was previously unrecognized. In addition, it is shown that the term in $cos\ensuremath{\phi}$ has no effect upon rf-induced steps in the time-averaged current-voltage curve for a tunneling junction biased by a voltage source. Finally a relation is discussed between tunneling and other experiments such as far-infrared absorption and acoustic attenuation in superconductors. It is shown that tunneling can be thought of in terms of a slight generalization of the coherence effects which dominate the other kinds of experiments.

105 citations


Patent
26 Jul 1974
TL;DR: In this paper, an electromagnetic energy collection device is provided which does not require a solar tracking capability and includes an energy receiver positioned between two side walls which reflect substantially all incident energy received over a predetermined included angle directly onto the energy receiver.
Abstract: An electromagnetic energy collection device is provided which does not require a solar tracking capability. It includes an energy receiver positioned between two side walls which reflect substantially all incident energy received over a predetermined included angle directly onto the energy receiver.

99 citations


Journal ArticleDOI
TL;DR: In this paper, the authors measured the absolute cross section for the excitation in the 391.4-nm band from impact of electrons on ions in various state mixtures.
Abstract: Crossed beams of ${\mathrm{N}}_{2}^{+}$ and electrons were used to measure the absolute cross sections for the excitation, $\mathrm{N}_{2}^{}{}_{}{}^{+}(X^{2}\ensuremath{\Sigma}_{g}^{+}, v=0)+e\ensuremath{\rightarrow}\mathrm{N}_{2}^{}{}_{}{}^{+}(B^{2}\ensuremath{\Sigma}_{u}^{+}, v=0)+e$, over an electron energy range from below threshold (3.17 eV) to 91 eV. Absolute emissions of the 391.4-nm band were measured from impact of electrons on ${\mathrm{N}}_{2}^{+}$ ions in various state mixtures. Corrections were made to the data to account for state mixtures and other effects to obtain the cross section for the above process. The cross section falls from its finite threshold value of 3.0 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}16}$ to 0.30 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}16}$ ${\mathrm{cm}}^{2}$ at 91 eV. The present values are more than an order of magnitude smaller than either the 1968 values of Lee and Carleton or the 1973 value of Daschenko et al. At threshold the Gaunt-factor formula of Seaton predicts a value only 45% of that measured, but at the highest energy, the predictions of the Seaton formula have converged to within 20% of the present values of the cross section. Rate coefficients calculated from the present measurements are consistent with the recent rate-coefficient measurements of McLean et al. Total uncertainty at high confidence is about 18%, taken as the quadrature sum of random uncertainty (15% at 98% confidence level) with systematic uncertainties (about 8% at high confidence). The analysis leading to interpretation of the emission cross section in terms of an excitation cross section between specific states is subject to uncertainties which are not well defined, and are not included in the stated uncertainty.

71 citations


Journal ArticleDOI
TL;DR: In this article, a self-consistent calculation of energy bands in lithium has been performed using the linear-combination-of-atomic-orbitals (LCAO) method.
Abstract: A self-consistent calculation of energy bands in lithium has been performed using the linear-combination-of-atomic-orbitals (LCAO) method. The basis set consisted of nine $s$-type, six $p$-type, and three $d$-type Gaussian orbitals. Exchange was included according to the $X\ensuremath{\alpha}$ method with $\ensuremath{\alpha}=\frac{2}{3}$. Results are presented for the band structure, Fermi-surface properties, cohesive energy, and the Compton profile. The interband contribution to the optical conductivity was calculated including the $\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}$ variation of the momentum matrix elements. The distortions of the Fermi surface from spherical symmetry are less than 4%. The optical and thermal effective-mass ratios are 1.48 and 1.53, respectively. The onset of direct interband transitions is predicted to occur at 3.28 eV. The calculated cohesive energy is 0.124 Ry.

Journal ArticleDOI
TL;DR: In this article, a method for the calculation of the leading term of a previously proposed low-density expansion for the self-energy of nucleons in nuclear matter was described, where the single-particle complex potential energy, the average binding energy per nucleon, the complex symmetry potential, and the symmetry energy was calculated.
Abstract: We describe a method for the calculation of the leading term of a previously proposed low-density expansion for the self-energy of nucleons in nuclear matter. We compute the single-particle complex potential energy, the average binding energy per nucleon, the complex symmetry potential, and the symmetry energy. We use Reid's hard core nucleon-nucleon interaction and take a Fermi momentum ${k}_{F}=1.4$ ${\mathrm{fm}}^{\ensuremath{-}1}$. The calculated single-particle potential energy is compared with the phenomenological values of the optical-model potential in the inner region of a nucleus. The real part of our theoretical value is given by $56\ensuremath{-}0.3E$ (MeV) below $E=150$ MeV, and changes sign at 200 MeV. The imaginary part rises from 2 MeV at low energy to about 20 MeV at $E=200$ MeV. These features are in good agreement with experimental evidence. The average binding energy $B$ per nucleon calculated with a self-consistent potential energy for the particle states above ${k}_{F}$ is equal to -11 MeV. In the standard approach, with no potential energy for intermediate particle states above ${k}_{F}$, one finds -8.65 MeV. We also calculate the symmetry potential. At low energy, its real part is equal to $14 \frac{(N\ensuremath{-}Z)}{A}$ (MeV); it changes sign at 110 MeV. Its imaginary part is equal to $3.5\frac{(N\ensuremath{-}Z)}{A}$ (MeV) at low energy, and rises to $8.5\frac{(N\ensuremath{-}Z)}{A}$ (MeV) at 200 MeV. The symmetry energy is equal to 27.8 MeV.NUCLEAR REACTIONS Calculated complex optical-model potential, symmetry potential, average binding energy and symmetry energy for nucleons in nuclear matter, for a Fermi momentum equal to 1.4 ${\mathrm{fm}}^{\ensuremath{-}1}$, from Reid's hard core nucleon-nucleon interaction, in the frame of Brueckner's theory.

Journal ArticleDOI
TL;DR: In this paper, measurements of the electroproduction reaction were carried out at the Wilson Synchrotron Laboratory and the results for the pion electromagnetic form factor up to 2.15$ GeV were reported.
Abstract: Measurements of the electroproduction reaction ${e}^{\ensuremath{-}}+p\ensuremath{\rightarrow}{e}^{\ensuremath{-}}+{\ensuremath{\pi}}^{+}+n$ carried out at the Wilson Synchrotron Laboratory are reported. For fixed virtual photon-hadron center-of-mass energy, $W=2.67$ GeV, data are presented with the mass of the virtual photon, $\ensuremath{-}{k}^{2}$, centered at 0.6, 1.2, and 2.0 Ge${\mathrm{V}}^{2}$. At the central $\ensuremath{-}{k}^{2}=1.2$ ${(\mathrm{GeV})}^{2}$ point, results are also given for $W=2.15$ GeV. For the $W=2.67$, $\ensuremath{-}{k}^{2}=1.2$ Ge${\mathrm{V}}^{2}$ setting, an angular scan is presented and the longitudinal transverse-interference term is extracted. The data are compared with an electron Born-model calculation of Berends which has as its only free parameter the pion electromagnetic form factor. The theory is used to extract new results for the pion form factor up to $\ensuremath{-}{k}^{2}=2.0$ Ge${\mathrm{V}}^{2}$.

Journal ArticleDOI
TL;DR: The valence-band structure and the semiconducting properties of the compound AgX{Ag}X{Te}{Te}}_{2}$ (X=\mathrm{A}\mathrm {l,\phantom{\rule{0ex}{0ex}}\mathm{G}{a, \phantom''{I}{n}$) compounds have been studied.
Abstract: The valence-band structure and the semiconducting properties of the $\mathrm{Ag}X{\mathrm{Te}}_{2}$ ($X=\mathrm{A}\mathrm{l},\phantom{\rule{0ex}{0ex}}\mathrm{G}\mathrm{a},\phantom{\rule{0ex}{0ex}}\mathrm{I}\mathrm{n}$) compounds have been studied. At 77 \ifmmode^\circ\else\textdegree\fi{}K, AgAl${\mathrm{Te}}_{2}$ and AgIn${\mathrm{Te}}_{2}$ have direct energy gaps located at 2.35 eV and 1.04 eV, respectively. AgGa${\mathrm{Te}}_{2}$ has a direct energy gap at 1.36 eV, which is probably the lowest energy gap. All three compounds can be made usefully $p$ type, but only AgIn${\mathrm{Te}}_{2}$ has been made $n$ type.

Journal ArticleDOI
M. Tinkham1
TL;DR: In this paper, the London-Ginzburg-Landau concept of superconductivity as a macroscopic quantum state is reviewed, and experimental measurements are discussed of resistance below T c, and of enhanced diamagnetism above T c, both caused by thermodynamic fluctuations away from the Ginzburglandau state of lowest free energy.
Abstract: The London-Ginzburg-Landau concept of superconductivity as a macroscopic quantum state is reviewed. Experimental measurements are then discussed of resistance below ${T}_{c}$, and of enhanced diamagnetism above ${T}_{c}$, both caused by thermodynamic fluctuations away from the Ginzburg-Landau state of lowest free energy. Next the limitations on superconductivity at nonzero frequencies are reviewed: normal electron dissipation $\ensuremath{\propto}{\ensuremath{\omega}}^{2}$, and strong absorption above the energy gap frequency. Sum rule arguments relate the superfluid response at low frequencies to the gap; effects of strong electron-phonon coupling are also found. Finally, results of recent work on the resistive state of superconducting filaments above the critical current are summarized.

Journal ArticleDOI
TL;DR: In this article, the authors compared the results of these experiments with other nuclides at approximately the same energy and were used to illustrate phenomena occurring in intermediate-energy $ensuremath{\alpha}$ scattering to which they have given the name "refractive behavior."
Abstract: We report on recent $\ensuremath{\alpha}$-scattering experiments at 141.7 MeV using $^{40}\mathrm{Ca}$ and $^{90}\mathrm{Zr}$ targets. The results are compared with previous experiments on other nuclides at approximately the same energy and are used to illustrate phenomena occurring in intermediate-energy $\ensuremath{\alpha}$ scattering to which we have given the name "refractive behavior." All the elastic scattering differential cross sections exhibit the exponential-like falloff at large angles characteristic of nuclear rainbow scattering. The variation in the rainbow angle with $A$ is found to be approximately linear. In each instance it is shown that, consistent with earlier predictions, it is the data beyond the rainbow angle which make possible the elimination of the discrete ambiguities in the optical potential: For each nucleus studied, only a single family of Woods-Saxon optical potentials is found to fit the data. The real parts of the extracted potentials are characterized by well depths ranging from 108 to 118 MeV and volume integrals $\frac{J}{4A}$ ranging from 297 to 352 MeV ${\mathrm{fm}}^{3}$; hence they are more nearly three times the strength of nucleon-nucleus potentials at 1/4 the incident energy, rather than 4 times, as is frequently assumed. Systematic variations of the optical potentials with $A$ occur primarily in the imaginary part of the potential and are greatest for the lighter nuclei; as $A$ decreases, $W$ and ${a}^{\ensuremath{'}}$ decrease, $r_{0}^{}{}_{}{}^{\ensuremath{'}}$ increases, and the volume integral of the real part of the potential increases.NUCLEAR REACTIONS $^{40}\mathrm{Ca}$, $^{90}\mathrm{Zr}(\ensuremath{\alpha},\ensuremath{\alpha})$, $E=141.7$; enriched targets; measured $\ensuremath{\sigma}(\ensuremath{\theta})$; deduced optical-model parameters, nuclear rainbow angles; results compared with those from $^{58}\mathrm{Ni}$, $^{12}\mathrm{C}$.

Journal ArticleDOI
TL;DR: In this paper, a new approach to pion production is explored in the threshold region, where the authors treat the pion-deuteron elastic scattering system as a three-body system, with absorption (or production) occurring because of the existence of a $\ensuremath{\pi}N$ bound state in the nuclear channel.
Abstract: Some consequences of a new approach to pion production are explored in the threshold region. We treat the $\ensuremath{\pi}\mathrm{NN}$ system as a three-body system, with absorption (or production) occurring because of the existence of a $\ensuremath{\pi}N$ bound state in the ${P}_{11}$ (nucleon) channel. This description of the $\mathrm{NN}\ensuremath{\pi}$ vertex is justified by successfully using the model to calculate the long range part of the $N\ensuremath{-}N$ scattering amplitude. The results of the pion production calculation confirm a sensitivity to the short range behavior of the deuteron wave function and its $D$-state probability reported earlier. We also find a stronger variation of the production amplitude with energy than has previously been reported. This may resolve the apparent incompatibility of some experimental results. Finally, we also discuss the implications of the model for pion-deuteron elastic scattering.NUCLEAR REACTIONS $\mathrm{pp}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}d$, ${E}_{\ensuremath{\pi}}=0\ensuremath{-}30$ MeV; $s$-wave pions, calculated $\ensuremath{\sigma}$ as function of ${E}_{\ensuremath{\pi}}$, also dependence on $N\ensuremath{-}N$ interaction. $d(\ensuremath{\pi}, \ensuremath{\pi})$; calculated scattering length, including absorption. Faddeev calculation, separable interactions.

Journal ArticleDOI
TL;DR: In this paper, the energy region above 1 GeV is subjected to search for characteristic points, their significance is discussed, and a strange and unlikely correlation between them and the masses of lower energy physics is pointed out.

Journal ArticleDOI
TL;DR: In this paper, the Ambegaokar-Halperin theory was generalized to include the pair-quasiparticle interference term and it was concluded that a measurement of the $cos\ensuremath{-}V$ term using only the $I\en-V$ characteristic will be difficult.
Abstract: Measurements are reported of the current-voltage ($I\ensuremath{-}V$) characteristics of externally shunted oxide-barrier tunnel junctions at temperatures $T$ and critical currents ${I}_{c}$ such that the Josephson coupling energy $(\frac{\ensuremath{\hbar}}{2e}){I}_{c}$ is comparable to the thermal energy $kT$. The measurements are in complete quantitative agreement with the theory of Ambegaokar and Halperin in the limit that the dimensionless parameter ${\ensuremath{\beta}}_{c}=(\frac{2e}{\ensuremath{\hbar}})(\frac{{I}_{c}C}{{\ensuremath{\sigma}}^{2}})\ensuremath{\ll}1$, where $C$ is the capacitance and $\ensuremath{\sigma}$ the total conductance of the shunted junction. Measurements for larger values of ${\ensuremath{\beta}}_{c}$ are in qualitative agreement with the theory of Kurkij\"arvi and Ambegaokar. In addition, the Ambegaokar-Halperin theory is generalized to include the $cos\ensuremath{\phi}$ pair-quasiparticle interference term. It is concluded that a measurement of the $cos\ensuremath{\phi}$ term using only the $I\ensuremath{-}V$ characteristic will be difficult.

Journal ArticleDOI
TL;DR: In this article, the authors studied the dynamics of the classical Heisenberg chain at finite and infinite temperatures by computer simulation of an array of 4000 spins and derived the spin-spin and energy-energy wavevector-and time-dependent correlation functions.
Abstract: We have studied the dynamics of the classical Heisenberg chain at finite and infinite temperatures by computer simulation of an array of 4000 spins. The evaluation of the spin-spin and energy-energy wave-vector- and time-dependent correlation functions out to time $10{J}^{\ensuremath{-}1}$ made it possible to determine the spin and energy diffusion constants. At infinite temperature we find ${D}_{S}=(1.33\ifmmode\pm\else\textpm\fi{}0.10)JS{a}^{2}$ and ${D}_{E}=(3\ifmmode\pm\else\textpm\fi{}1)JS{a}^{2}$. Values of ${D}_{S}$ have also been determined, with less precision, for ferromagnetic and antiferromagnetic interactions at temperatures $\frac{{k}_{B}T}{|J|}=1.0 \mathrm{and} 0.5$. Our results are compared with various theoretical estimates. In addition, we calculate the time-dependent spin and energy self-correlation functions.

Journal ArticleDOI
TL;DR: In this article, a configurational-coordinate diagram was proposed for the extrinsic optical absorption associated with defects in GaAs between 4 and 300mmode in the range from 0.6 to 1.5 eV, where the absorption curves of each line appear to be Gaussian at every temperature.
Abstract: The extrinsic optical absorption associated with defects in GaAs has been studied between 4 and 300\ifmmode^\circ\else\textdegree\fi{}K in the range from 0.6 to 1.5 eV. Two bands in particular are investigated: the first located around 0.9 eV is associated with chromium; the second at 1.2 eV, present in all materials, is probably related to some native defects such as gallium vacancies. The variations of the energy and of the shape of these two bands versus temperature demonstrate that they cannot come from transitions between extrinsic levels and the energy bands of the perfect crystal. The absorption curves of each line appear to be Gaussian at every temperature. As a consequence of lattice coupling, the width of these bands increases greatly with temperature according to a law: $W(T)=W(0)$ ${[coth(\frac{h\ensuremath{ u}g}{2kT})]}^{\frac{1}{2}}$. Finally, it is shown that a configurational-coordinate diagram may be applied to these two centers. On this basis, we give the values of the quantum energy of vibration of the centers in their ground states $h\ensuremath{ u}g:13$ meV for the chromium center, and 15 meV for the center at 1.2 eV. For this last one, we propose a configurational-coordinate diagram assuming the parabolic approximation to be valid. These results are discussed and compared with those obtained by photoconductivity or photoluminescence in GaAs, taking into account the important Stokes shift resulting from the lattice coupling we mentioned above. In particular, it is shown that the center absorbing at 1.2 eV is quite different of that emitting at 1.2 eV, i.e., the ${V}_{\mathrm{Ga}}:D$ complex for which Williams has already proposed a configurational-coordinate diagram.

Journal ArticleDOI
TL;DR: In this paper, a high-resolution electron time-of-flight spectrometer was used to measure the vibrational resonance of the electron in the energy range 50-300 meV.
Abstract: Resonances in the $e\ensuremath{-}{\mathrm{O}}_{2}$ total cross section in the energy range 50-300 meV were studied with a high-resolution ($\ensuremath{\Delta}El10$ meV) electron time-of-flight spectrometer. Each vibrational resonance was found to have a well-resolved doublet structure, which has not previously been observed, and which is due to spin-orbit coupling in the $^{2}\ensuremath{\Pi}_{g}$ ground state of ${\mathrm{O}}_{2}^{\ensuremath{-}}$. The spin-orbit coupling constant of ${\mathrm{O}}_{2}^{\ensuremath{-}}$ was measured to be $|A|=20\ifmmode\pm\else\textpm\fi{}2 \mathrm{meV}=161\ifmmode\pm\else\textpm\fi{}16 {\mathrm{cm}}^{\ensuremath{-}1}$, in agreement with theoretical estimates. On an energy scale established from the measured electron flight times, the energy of the center of the ${v}^{\ensuremath{'}}=4$ resonance was measured to be 91 \ifmmode\pm\else\textpm\fi{} 5 meV. This value is in agreement with a recent photodetachment measurement of the electron affinity of ${\mathrm{O}}_{2}$, and with a previously observed accidental coincidence between the $v=3$ level of ${\mathrm{O}}_{2}$ and the ${v}^{\ensuremath{'}}=8$ level of ${\mathrm{O}}_{2}^{\ensuremath{-}}$. The electron time-of-flight spectrometer is described in detail.

Journal ArticleDOI
TL;DR: In this paper, Brillouin-scattering measurements have been performed on potassium dihydrogen phosphate (KDP) in the temperature range $113lTl291$ \ifmmode^\circ\else\textdegree\fi{}K with electric fields between 0 and 3937 V/cm.
Abstract: Brillouin-scattering measurements have been performed on potassium dihydrogen phosphate (KDP) in the temperature range $113lTl291$ \ifmmode^\circ\else\textdegree\fi{}K with electric fields between 0 and 3937 V/cm. Values of the adiabatic $x\ensuremath{-}y$ shear elastic constant ${c}_{66}^{E,S}$ deduced from the experiment are presented in tabular form. The data are compared with the predictions of several free-energy expressions. The Slater-SUS (Silsbee, Uehling, and Schmidt) theory is shown to predict values of the elastic constant in reasonable agreement with the experimental values, but the SUS parameters which provide the best fit to the elastic-constant data are somewhat different from those which give a best fit to spontaneous-polarization data. The data are also compared to the predictions of three phenomenological free-energy expressions which are all variants of the Landau-Devonshire power-series expansion. The simple molecular-field expression is shown to give poor agreement with the ${c}_{66}^{E,S}$ data, and to require parameter values for even a poor fit which then predict unreasonably large values for the spontaneous polarization. Two other phenomenological free energies are considered, one having a tenth-power nonlinear polarization term and predicting a second-order transition, and another, proposed by Benepe and Reese, having fourth-and eighth-power nonlinear polarization terms and predicting a slightly first-order transition. These two phenomenological free energies have previously been utilized in the analysis of various thermodynamic properties of KDP, and it is found that both are able to predict values for the elastic constant ${c}_{66}^{E,S}$ in reasonable agreement with experiment while providing adequate predictions for the spontaneous polarization with the same parameters. The behavior of ${c}_{66}^{E,S}$ within 0.1 \ifmmode^\circ\else\textdegree\fi{}K of the transition, however, favors the Benepe-Reese free energy.

Patent
01 Jul 1974
TL;DR: In this article, a communication system comprising a transmitter for radiating a carrier frequency signal, which may be modulated, to a data station is presented, which includes a rectifier for rectifying the received carrier signal to provide energy to the station elements.
Abstract: A communication system comprising a transmitter for radiating a carrier frequency signal, which may be modulated, to a data station. The station includes a rectifier for rectifying the received carrier signal to provide energy to the station elements. A data source at the station produces a data signal representative of the information to be transmitted. A harmonic generator produces harmonics of the carrier signal and the harmonic signal is modulated with the data or information signal. An antenna radiates the modulated harmonic signal to a receiver which demodulates the received signal to extract the information therefrom. Thus, a completely self-contained and economic system is provided, since the carrier signal per se supplies the energy to operate the data station. Additionally, the communication system may include a carrier signal having an address encoded therein and the station may comprise an address decoder so that only a selected addressed station will transmit the desired data at any one time.

Journal ArticleDOI
TL;DR: In this article, electron tunneling through $n$-type PbTe-oxide-Pb junctions was used to measure some electronic properties of the (100) surface accumulation layer at the Pb-oxide interface.
Abstract: Using electron tunneling through $n$-type PbTe-oxide-Pb junctions, we have measured some electronic properties of the (100) surface accumulation layer at the PbTe-oxide interface. Three energy levels, resulting from quantization of the electronic motion normal to the surface, are observed in a sample having $n=1.2\ifmmode\times\else\texttimes\fi{}{10}^{18}$ /${\mathrm{cm}}^{2}$. The energies of these three levels are ${E}_{0}=42$ meV, ${E}_{1}=19$ meV, and ${E}_{2}=6$ meV below the conduction band edge. From the magnetotunneling data we obtain ${g}^{*}=29\ifmmode\pm\else\textpm\fi{}3$ and ${m}^{*}=(0.069\ifmmode\pm\else\textpm\fi{}0.008){m}_{0}$ for the ground-state subband. In addition, the Landau levels in the ground-state subband do not cross the Landau levels in the excited-state subband. The interaction between the Landau levels removes the degeneracy at the crossover and a splitting, $\ensuremath{\Delta}E\ensuremath{\approx}4$ meV, has been observed.

Journal ArticleDOI
TL;DR: In this paper, the authors derive the rules for computing the centroid energy in a linked-cluster expansion, and give some examples of the relation of the mean removal energy to Brandow's self-consistent orbital energy.
Abstract: A useful way to characterize the hole-energy spectrum excited in a direct particle-removal reaction like ($p,2p$) or ($e,{e}^{\ensuremath{'}}p$) is through the centroid or mean removal energy. We derive the rules for computing this quantity in a linked-cluster expansion, and give some examples. We demonstrate the close relation of the mean removal energy to Brandow's self-consistent orbital energy, and discuss briefly the connection with Green's function theory.[NUCLEAR STRUCTURE Linked-cluster theory of mean or centroid removal energies measured in ($p,2p$) or ($e,{e}^{\ensuremath{'}}p$); applications and relation to other hole energies.]

Journal ArticleDOI
TL;DR: In this article, the field-emission measurements of the total energy distribution from a clean metal surface are shown to provide information about the density of states near the surface, where the authors show that the current per unit energy at energy is given approximately by $j(ensuremath{\omega}):
Abstract: Field-emission measurements of the total-energy distribution from a clean metal surface are shown to provide information about the density of states near the surface. Specifically, we find the field-emitted current per unit energy at energy $\ensuremath{\omega}$ to be given approximately by $j(\ensuremath{\omega})\ensuremath{\simeq}(\frac{2\ensuremath{\hbar}}{m})S{\ensuremath{\lambda}}^{\ensuremath{-}2}(\ensuremath{\omega})\ensuremath{\Sigma}{m}^{}{D}_{0}^{2}({E}_{\ensuremath{\perp}}^{m})\ifmmode\times\else\texttimes\fi{}{|{\ensuremath{\psi}}_{m}({x}_{m})|}^{2}\ensuremath{\delta}(\ensuremath{\omega}\ensuremath{-}{\ensuremath{\epsilon}}_{m})$, where ${D}_{0}^{2}$ is the usual barrier-penetration probability with image potential corrections, ${E}_{\ensuremath{\perp}}^{m}=\ensuremath{\omega}\ensuremath{-}\frac{{\ensuremath{\hbar}}^{2}{k}_{\ensuremath{\parallel}}^{2}}{2m}$, where ${k}_{\ensuremath{\parallel}}$ is the electron momentum parallel to the surface, $|{\ensuremath{\psi}}_{m}({x}_{m})|$ is the amplitude of the metal electron at the classical turning point (${x}_{m}\ensuremath{\sim}1\ensuremath{-}2$ \AA{}A), $\ensuremath{\lambda}(\ensuremath{\omega})$ is a slowly varying function of $\ensuremath{\omega}$, and $S$ is the metal surface area. The ${D}_{0}^{2}$ factor in $j(\ensuremath{\omega})$ strongly weights electron states with small ${k}_{\ensuremath{\parallel}}$ and consequently $j(\ensuremath{\omega})$ measures the density of states at ${x}_{m}$ arising from the component of the bulk band structure normal to the surface. Measurements of $j(\ensuremath{\omega})$ for several single-crystal planes of tungsten will be presented and compared to the relevant photoemission data.

Journal ArticleDOI
TL;DR: In this paper, a model for describing the ligand-field spectra of cubic chromophores in a molecular orbital basis is derived and tested by carrying out least-squares-fits of the spectra for the tetrahedral ions CoX$\{4}^{2-}$ (X = Cl, Br).
Abstract: A model for describing the ligand-field spectra of cubic chromophores in a molecular orbital basis is derived and tested by carrying out least-squares-fits of the spectra of the tetrahedral ions CoX$\_{4}^{2-}$ (X = Cl, Br). Independent assignments of the ligand-field spectra of the latter ions are obtained by analysing the site-group splittings and vibrational fine-structure in the polarized spectra of Cs$\_{3}$CoCl$\_{5}$ and Cs$\_{3}$CoBr$\_{5}$ at 4.2 K. General expressions are calculated for the electron repulsion matrix elements of pairs of electrons occupying orbitals transforming as e, t$\_{1}$ and t$\_{2}$ in O$\_{\text{h}}$ and T$\_{\text{d}}$ point groups, without further assumption about the functional form of the orbitals. Tanabe & Sugano's (1954) matrices for d$^{1}$-d$^{5}$ configurations are rewritten in the more general form. The two-electron reduced matrix elements appearing in these expressions are further approximated in terms of orbital overlap populations (Mulliken 1955), one-and two-centre coulomb integrals and one-centre exchange integrals. An analogous reduction of the matrix elements of the molecular spin-orbit operator within a molecular orbital basis is also described. The energies of the spin-orbit baricentres of the ligand-field transitions are then calculated as functions of three orbital population parameters and the energy separation between the e and t$\_{2}$ molecular orbitals. From the least-squares analysis of the independently assigned experimental spectra, empirical values of the four parameters are extracted, and their relation to the parameters of conventional ligand-field theory is discussed. The experimentally based molecular orbital parameters are further used to calculate spinorbit splittings of the cubic Russell-Saunders ligand-field states, and the relative dipole strengths of transitions to those which are formally spin-forbidden from the ground state.

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TL;DR: In this article, the energy released by removing an electron from the $4f$ level to the conduction band (0.01-0.1 eV) depends significantly on the number of La nearest neighbors.
Abstract: The recoilless-absorption spectra of the 21.6-keV $\ensuremath{\gamma}$ rays of ${\mathrm{Eu}}^{151}$ in ${\mathrm{Eu}}_{x}{\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Rh}}_{2}$ are composed of a few lines which exhibit strongly temperature-dependent isomer shifts. The results are interpreted in terms of fast fluctuations of electrons between a localized $4f$ level and the conduction band. The energy released by removing an electron from the $4f$ level to the conduction band (0.01-0.1 eV) depends significantly on the number of La nearest neighbors. The levels have a width of \ensuremath{\sim} 0.01 eV.

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TL;DR: In this paper, critical fluctuations in kinetic Ising models are interpreted in terms of cluster reactions, and the basic assumption that clusters with $l$ spins grow at a rate is tested by Monte Carlo computations in the single-spin-flip case.
Abstract: Critical fluctuations in kinetic Ising models are interpreted in terms of cluster reactions The basic assumption, that clusters with $l$ spins grow at a rate $\ensuremath{\propto}{l}^{r}$, is tested by Monte Carlo computations in the single-spin-flip case The dynamic susceptibilities associated with order parameter and energy are then calculated also for nonzero magnetic field, and are shown to fulfill dynamic scaling The exponent $(2\ensuremath{-}r)\ensuremath{\beta}\ensuremath{\delta}$ of the relaxation times can be different from the susceptibility exponent $\ensuremath{\gamma}$