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Showing papers on "Doppler broadening published in 1988"


Journal ArticleDOI
TL;DR: In this paper, the optical absorption spectrum of an excess electron solvated in a molecular sample of liquid water at 300 K was calculated with use of solvent configurations generated via path-integral simulation and subsequent solution of the excess-electronic eigenvalue problem.
Abstract: The optical-absorption spectrum of an excess electron solvated in a molecular sample of liquid water at 300 K has been calculated with use of solvent configurations generated via path-integral simulation and subsequent solution of the excess-electronic eigenvalue problem. Electronic transitions from an s-like ground state to three bound-localized, p-like excited states dominate the broad asymmetric spectrum with excitations into an apparent continuum following at higher energy. Asymmetric distortions and radial fluctuations of the solvent cavities contribute comparably to the spectral broadening.

163 citations


Journal ArticleDOI
TL;DR: In this article, complete resonance Raman spectra, including absolute cross sections, have been measured for CS2 in cyclohexane using four excitation wavelengths from 223 to 204 nm, on resonance with the strongly allowed S3←S0 electronic transition.
Abstract: Complete resonance Raman spectra, including absolute cross sections, have been measured for CS2 in cyclohexane using four excitation wavelengths from 223 to 204 nm, on resonance with the strongly allowed S3←S0 electronic transition. Absolute intensities have also been measured in CS2 vapor using 200 nm excitation. These total Raman cross sections, together with the Rayleigh cross sections calculated from the Kramers–Kronig transform of the absorption spectrum, are used to determine the homogeneous linewidth Γ for the electronic transition under the assumption that the solvent induced broadening may be partitioned into a static, inhomogeneous part and a very rapidly modulated, homogeneous component. Γ is found to be ∼13 cm−1 in the vapor and ∼200 cm−1 in cyclohexane solution, indicating that homogeneous broadening is responsible for much of the increase in spectral breadth between vapor and solution phases. Direct modeling of the solution phase absorption spectrum and the intensities of the lower lying Ram...

101 citations


Journal ArticleDOI
TL;DR: This analysis shows that this sub-Doppler structure is broadened by the residual Doppler effect for non-normal incidence, and predicts a conventional Voigt-type dispersion response, based on the complex-refractive-index approach.
Abstract: We calculate the reflection coefficient for a light beam incident on the interface between a dielectric and a resonant atomic vapor to first order in the dipole polarization in the vapor. The angle of incidence and the polarization direction are chosen arbitrarily, and saturation is fully accounted for. The atoms are supposed to get deexcited at collisions with the surface. The resulting transient behavior of atoms leaving the surface is responsible for a nonlocal response. This spatial dispersion near the surface is known to produce a natural-linewidth-limited resonance in the vapor reflection coefficient at normal incidence. Our analysis shows that this sub-Doppler structure is broadened by the residual Doppler effect for non-normal incidence. This structure disappears at the critical angle for total internal reflection, where one predicts a conventional Voigt-type dispersion response, based on the complex-refractive-index approach. We also calculate the saturation broadening of the atomic response for large intensities. Beyond the critical angle, the spectral response suddenly shifts from dispersion to absorption line shapes. In the case of total internal reflection, the spatial dispersion leads to an additional Lorentzian broadening, which results from an effective imaginary Doppler shift at passage through the evanescent wave (transit-time broadening).

98 citations


Journal ArticleDOI
TL;DR: In this paper, an experimental and theoretical study of the gain experienced by a weak probe beam propagating through a sodium vapor in the presence of an intense pump field that is nearly resonant with the 3s → 3p atomic transition is presented.
Abstract: We present the results of an experimental and theoretical study of the gain (or absorption) experienced by a weak probe beam propagating through a sodium vapor in the presence of an intense pump field that is nearly resonant with the 3s → 3p atomic transition. The probe-transmission spectrum includes three distinct features that result from the modification of the atomic-level structure by the ac-Stark effect. Two of these features can lead to amplification of the probe wave. We measured the dependence of the probe spectrum on the detuning of the pump beam from resonance and on the pressure of a helium buffer gas. The experimentally obtained spectra are in good agreement with the predictions of a theoretical model based on the solution of the density-matrix equations of motion for a two-level atom and including the effects of Doppler broadening. The maximum gain measured in these experiments occurs at one of the Rabi sidebands and leads to a 38-fold increase in the intensity of the probe wave. Under some experimental conditions, we also observed two additional resonances, which are due to stimulated Raman scattering involving the sodium ground-state hyperfine levels.

64 citations


Journal ArticleDOI
TL;DR: In this article, the results of nonlinear tearing mode dynamics in reversed field pinch plasmas are described, where the resonant surfaces are in the plasma core and the linear instabilities have poloidal mode number m=1 and toroidal mode numbers 10≲n≲20.
Abstract: The results of investigations of nonlinear tearing‐mode dynamics in reversed field pinch plasmas are described. The linear instabilities have poloidal mode number m=1 and toroidal mode numbers 10≲n≲20, and the resonant surfaces are therefore in the plasma core. The nonlinear dynamics result in dual cascade processes. The first process is a rapid m=1 spectral broadening toward high n, with a simultaneous spreading of magnetic turbulence radially outward toward the field‐reversal surface. Global m=0 perturbations, which are driven to large amplitudes by the m=1 instabilities, in turn trigger the m=1 spectral broadening by back coupling to the higher n. The second process is a cascade toward large m and is mediated by m=2 modes. The m=2 perturbations have the structure of localized, driven current sheets and nonlinearly stabilize the m=1 modes by transferring m=1 energy to small‐scale dissipation. The calculated spectrum has many of the qualitative features observed in experiments.

62 citations


Journal ArticleDOI
TL;DR: In this paper, the ability of available theoretical models in describing broadening mechanisms is tested for the CO2 O2, CO2 CO 2, CO 2 CO 2 and CO 2 N 2 systems, and it is shown that short-range forces can contribute significantly to broadening.
Abstract: The ability of available theoretical models in describing broadening mechanisms is tested for the CO2–O2, CO2–CO2, and CO2–N2 systems. It is shown that the Anderson–Tsao–Curnutte theory is inaccurate since short‐range forces can contribute significantly to broadening. We use the approach of Robert and Bonamy, but the usual expansion of the atom–atom potential to the fourth order around the intermolecular distance appears insufficient at short distances for these particular systems. We propose a better representation of the radial dependence of the atom–atom potential, while keeping the previous analytical expression of the cross section. Satisfactory results are obtained for both the rotational quantum number dependence of room‐temperature CO2–O2, CO2–CO2, and CO2–N2 half‐widths and the evolution of CO2–N2 broadening with temperature. It is shown that the isotropic part of the potential involved in the trajectory calculation must be coherently deduced from the atom–atom interaction potential.

52 citations


Journal ArticleDOI
TL;DR: In this article, Bernath et al. compared simulated CH and CN absorption line profiles for high-temperature (T = 1200 K) thermal broadening and for a combination of lowtemperature thermal plus turbulent broadening at a lambda/Delta-lambda ratio of about 100,000.
Abstract: Recent high-resolution observations of interstellar absorption lines of CH and CN toward Zeta Oph obtained by Crane et al. (1986), and Palazzi et al. (1988), exhibit line widths that suggest thermal line broadening at high temperature, T about 1200 K. Observations of CO line emission at 2.6 mm toward Zeta Oph (Langer et al.,1987) indicate that the molecular gas resides in four distinct velocity components that span less than 3 km/s in Doppler velocity. Simulated CH and CN absorption line profiles are compared for high-temperature (T = 1200 K) thermal broadening and for a combination of low-temperature (T = 50 K) thermal plus turbulent broadening. It is shown that the two broadening models reproduce existing observations comparably well and are virtually indistinguishable at a lambda/Delta-lambda ratio of about 100,000. The observed differences in the CH and CN line widths may reflect slightly different distributions of those molecules along the line of sight. The simulations use very recent, improved laboratory spectroscopic data on CH (Bernath). Some related consequences of such unresolved velocity structure on the ultraviolet absorption lines of CO are examined. Indirect diagnostics of temperature in the Zeta Oph cloud favor low-temperature thermal plus turbulent broadening, and the implied rate of dissipation of turbulence is in harmony with estimates of the global input of mechanical energy into to interstellar medium.

43 citations


Journal ArticleDOI
TL;DR: In this paper, two different source mechanisms that can cause the spectral broadening of VLF radio signals traversing the ionosphere, a phenomenon first observed by Bell et al. are proposed.
Abstract: Two different source mechanisms that can cause the spectral broadening of VLF radio signals traversing the ionosphere, a phenomenon first observed by Bell et al. (1983), are proposed. The first is a nonlinear scattering of the whistler-mode VLF signals by preexisting ionospheric density fluctuations that render a mode conversion to lower hybrid waves. In the absence of ionospheric irregularities, a second mechanism, that involves a parametric instability, can excite the lower hybrid waves, as was proposed by Lee and Kuo (1984). Since both types of spectra were recorded in experiments, it is concluded that the two suggested source mechanisms contribute additively to the observed spectral broadening of injected VLF waves.

40 citations


Journal ArticleDOI
TL;DR: In this paper, the authors determined the line shapes and intensities for coherent anti-Stokes Raman scattering (CARS) at saturation laser intensities by solving the time-dependent density-matrix equations numerically.
Abstract: Line shapes and intensities for coherent anti-Stokes Raman scattering (CARS) at saturation laser intensities are determined for nitrogen vibrational Q-branch lines by solving the time-dependent density-matrix equations numerically. We have previously performed measurements of saturated CARS line shapes in pure nitrogen by using nearly Fourier-transform-limited pump and Stokes lasers. The experimental laser pulse shapes, Stark effects, Doppler broadening, and the nonresonant background are incorporated in the numerical calculations. The numerical results show good agreement with the high-resolution measurements of saturated CARS line shapes. The lines show prominent saturation dips, and agreement between theory and experiment is excellent in terms of the depth and the width of the dips. The numerical results indicate that the Doppler effect tends to broaden and to deepen the dip in highly saturated lines, an effect that cannot be explained by a steady-state theory.

38 citations


Journal ArticleDOI
TL;DR: In this paper, the Doppler-broadened spectral line shape is distorted by the relative velocity between the neutral hydrogen atoms of the injected beam and impurity ions, and the calculation of the spectral intensity profiles using the available excitation rates overcorrects these discrepancies and indicates the need for better excitation coefficients.
Abstract: The use of charge exchange spectroscopy to determine plasma rotation speeds and ion temperature is complicated by the energy dependence of the excitation cross sections. The Doppler‐broadened spectral line shape is distorted by the relative velocity between the neutral hydrogen atoms of the injected beam and impurity ions. The asymmetric nature of the energy dependence of this cross section causes a nonmotional shift of the line center and a nonthermal change in the linewidth. These effects vary with the angles between the beam direction, rotation velocity direction, and direction of the viewing sightline. When viewing two neutral beams at different angles on TFTR, the two measurements of vφ(r) show discrepancies of about 20%–30% with each other. The calculation of the spectral intensity profiles using the available excitation rates overcorrects these discrepancies and indicates the need for better excitation coefficients.

37 citations


Journal ArticleDOI
TL;DR: In this article, a detailed analysis of this band for all four stable isotopic mixtures is given, including deuterides, for the vibrational bands, and the similarity of these constants to those of HeH+ in the ground state confirms that the observed states are Rydberg states.
Abstract: Spectra of helium hydride were observed after neutralization of a mass‐selected HeH+ beam. The molecules were produced in a fast beam, and so a special setup had to be used to avoid Doppler broadening and a careful calibration procedure had to be applied to determine the line positions and linewidths. In an earlier paper, we reported the first observation of a discrete spectrum of helium hydride, which was discovered by means of an emission band near 8000 A. In this paper, a detailed analysis of this band for all four stable isotopic mixtures is given. For the deuterides several vibrational bands were observed, which allowed equilibrium molecular constants to be determined. These constants agree with the results of recent ab initio calculations. The similarity of these constants to those of HeH+ in the ground state confirms that the observed states are Rydberg states. Comparison of the molecular constants for different isotopic mixtures shows deviations from the Born–Oppenheimer approximation. Born–Oppenheimer breakdown parameters were derived. Both the upper and lower states show predissociation to the repulsive ground state of helium hydride. The line intensities give evidence of a dependence of the electronic transition moment on the interatomic distance.

Journal ArticleDOI
TL;DR: In this article, the power deposition profiles during minority ion cyclotron heating are analyzed in large tokamaks by using the global toroidal wave code LION and a heuristic formula is given.
Abstract: The power deposition profiles during minority ion cyclotron heating are analysed in large tokamaks by using the global, toroidal wave code LION. For tokamaks with large aspect ratio and with circular cross-section, the wave is focused on the magnetic axis and can be absorbed there by cyclotron absorption when the cyclotron resonance passes through the magnetic axis. The power deposition profile is then essentially determined by the Doppler broadening of the ion cyclotron resonance. For equilibria either non-circular or with a small aspect ratio the power deposition profile depends also on the strength of the damping. In this case the power deposition profile can be expressed as a sum of two power deposition profiles. One is related to the power absorbed in a single pass, and its shape is similar to that obtained for large aspect ratio and circular cross-section. The other profile is obtained by calculating the power deposition in the limit of weak damping, in which case the wave electric field is almost constant along the cyclotron resonance layer. A heuristic formula for the power deposition is given. The formula includes a number of calibration curves and functions which has been calculated with the LION code for JET relevant equilibria. The formula enables calculation of the power deposition profile in a simple way when the launched wave spectrum and damping coefficients are known.

Journal ArticleDOI
TL;DR: In this article, the authors show how ultra high resolution (n, γ ) spectroscopy can be used to determine lifetimes of nuclear excited levels through the observation of Doppler broadening of deexciting transitions.

Patent
10 Jun 1988
TL;DR: In this article, a fiber-optical sensor used for measuring the Doppler broadening of scattered laser light by the principle of quasi-elastic light scattering (QELS) is presented.
Abstract: In a fiber-optical sensor used for measuring the Doppler broadening of scattered laser light by the principle of quasi-elastic light scattering (QELS), the scattered light originating from particles in movement, the emergence surface (7) for the laser light at the end of a single-mode or multimode light guide (3) used as an immersion probe is inclined at an angle 0<φ≦15°, preferably 1°≦φ≦6°, the angle of inclination being de-fined by the optical axis (8) of the light guide (3) and the normal (9) of the emergence surface (7).

Journal ArticleDOI
TL;DR: In this article, a pair of visible/near-UV spectrometers with eight viewing chords apiece have been installed on the DIII-D tokamak, each system views a neutral heating beam and can acquire up to 250 complete spectra from each chord with 5-20 ms time resolution.
Abstract: A pair of visible/near‐UV spectrometers with eight viewing chords apiece have been installed on the DIII‐D tokamak. Each system views a neutral heating beam and can acquire up to 250 complete spectra from each chord with 5–20‐ms time resolution. Each viewing chord covers 60 A with 0.27‐A spectral resolution, and the chords span about (2)/(3) of the plasma’s full width. By viewing Doppler‐broadened spectral lines from charge exchange recombination (CER) reactions between beam neutrals and plasma ions, ion temperatures up to 4 keV have been measured, and the bulk Doppler shift of these same lines has yielded plasma rotation velocities up to 200 km/s. The constancy of temperature on a magnetic flux surface and the rigid rotor model of a flux surface have been confirmed. These instruments have also been used to measure the neutral beam deposition profile, and preliminary experimental results agree with theoretical calculations of the beam deposition profile.

Journal ArticleDOI
TL;DR: In this article, the threshold current and its temperature (T) dependence in the range 200-400 K for AlGaAs quantum well lasers with 25-A wide GaAs wells using a model which includes lifetime broadening of the transitions and broadening the density of states function by fluctuations in the well width.
Abstract: We have calculated the threshold current and its temperature (T) dependence in the range 200–400 K for AlGaAs quantum well lasers with 25‐A‐wide GaAs wells using a model which includes lifetime broadening of the transitions and broadening of the density of states function by fluctuations in the well width. The threshold current varies approximately linearly with T and the principal effect of broadening is to increase the threshold current causing a reduction in the fractional change of current with temperature. The apparent value of the parameter T0 is increased to ≊400 K, compared with ≊320 K without broadening. The calculations are compared with experimental data.

Journal ArticleDOI
TL;DR: In this article, the authors measured the p(15N, αγ)12C nuclear reaction on a number of hydrogen-bearing gases to investigate the bond-dependent Doppler broadening resulting from the motion of the target hydrogen atoms.
Abstract: Excitation curves for the p(15N, αγ)12C nuclear reaction have been measured on a number of hydrogen-bearing gases to investigate the bond-dependent Doppler broadening resulting from the motion of the target hydrogen atoms. Contributions to the resonance width due to the intrinsic width of the resonance, gas-induced beam energy loss and energy straggle, accelerator beam energy spread, and Doppler broadening are considered. Calculations of Doppler broadening based on molecular spectroscopy data are presented.

Journal ArticleDOI
TL;DR: In this article, the magnetic field quenching of positronium (Ps) was studied in water and in benzene using in conjunction with lifetime spectroscopy and the Doppler broadening of the annihilation radiation lineshape techniques.

Journal ArticleDOI
TL;DR: Positron annihilation lifetimes and Doppler broadening lineshapes have been measured as a function of oxygen stoichiometry for YBa 2 Cu 3 O x (6.9> x >6.2), and it is concluded that the positron traps in this material are oxygen vacancies as mentioned in this paper.
Abstract: Positron annihilation lifetimes and Doppler broadening lineshapes have been measured as a function of oxygen stoichiometry for YBa 2 Cu 3 O x (6.9> x >6.2). It is found that the positron trapping rate is proportional to the oxygen vacancy concentration, and it is therefore concluded that the positron traps in this material are oxygen vacancies. Positrons are not expected to trap in oxygen vacancies unless the charge of the vacancy has been compensated. It is suggested that the charge on neighboring Cu ions is reduced in order to achieve this local charge compensation. The specific trapping rate is 4 orders of magnitude below that for vacancies in a metal. We tentatively propose that this is caused by a low positron mobility, due to the attraction of the positron to the negatively charged oxygen ions in the lattice. In addition, Doppler broadening lineshape studies of the superconducting transition in YBa 2 Cu 3 O 6.9 have been made. Below T c a large positive temperature dependence of the lineshape parameter is observed, while at T c a discontinuous increase in the lineshape parameter takes place. It is noted that the behaviour below T c may be consistent with a BCS-like theory if an energy band with a small dispersion crosses the Fermi level. The discontinuous increase is not clearly understood, but may be due to a major change in the electronic structure taking place concurrently with the onset of superconductivity.

Journal ArticleDOI
TL;DR: In this article, it was shown that the double-peaked emission line profiles in cataclysmic variables can be attributed to Doppler broadening caused by the Keplerian motion in geometrically thin accretion disks around white dwarfs.
Abstract: The frequent occurrence of double-peaked emission-line profiles in cataclysmic variables is generally interpreted as due to Doppler broadening caused by the Keplerian motion in geometrically thin accretion disks around white dwarfs. However, single-peaked profiles are frequently observed in many eclipsing systems that are viewed edge-on. Furthermore, broad wings are also present in some low-inclination systems that are observed nearly face-on. Simplified calculations for idealized disk models are presented that demonstrate that these features can be attributed to the Stark effect. Using these models, it is shown that the emission lines are generated over regions with temperatures 6000-9000 K and densities 10 to the 14th-17th/cu cm. From these parameters, the mass transfer rate and effective viscosity in the disk during the quiescent state can be deduced. Finally, it is shown that the evolution of emission-line profiles through eclipse can reveal basic parameters of the disk structure such as the temperature and surface density distribution. 30 references.

Journal ArticleDOI
TL;DR: In this article, a new method for measuring energy transfer between colliding molecules has been developed based upon the temperature dependence of the isotopic and hyperfine line widths of the Hg multiplet in the neighborhood of 254 nm.
Abstract: A new method for measuring energy transfer between colliding molecules has been developed. It is based upon the temperature dependence of the isotopic and hyperfine line widths of the Hg multiplet in the neighborhood of 254 nm. The light source was a Hg resonance lamp whose line profiles could be precisely controlled by varying the Hg pressure. Multiphoton absorption at 944 cm−1 was used to excite SF6 vibrationally during a 250 ns CO2 laser pulse. The subsequent rate of equipartition of this excess vibrational energy with the translational and rotational degrees of freedom was determined by measuring the initial slope of the increase in the absorption of 254 nm radiation by a trace of Hg vapor. It was found that pressures above 2 Torr were required to involve all of the SF6 molecules in the absorption of the laser radiation. The V→T, R energy transferred per SF*6 –SF6 collision was found to be proportional to the 3/2 power of the excitation energy between 1500 and 5000 cm−1 and gradually changed to a firs...

Journal ArticleDOI
TL;DR: In this paper, high-order diffraction of CW CO 2 laser radiation was observed in SF 6 in the Doppler broadening limit, and the nonlinear susceptibilities, up to χ (9), were separately monitored in DOppler free resonance lineshapes, using a nearcollinear phase matched multi-wave mixing configuration.

Journal ArticleDOI
TL;DR: In this article, the Doppler broadening of annihilation photons was found to be strongly influenced by x-ray irradiation, and the effect was extended homogeneously over the entire oxide layer.
Abstract: Variable‐energy positron‐beam studies have been carried out on Si with a 1.61 μm overlayer of SiO2 irradiated by x ray and γ ray up to the dose of 5×105 R. The Doppler broadening of annihilation photons was found to be strongly influenced by x‐ray irradiation, and the effect was extended homogeneously over the entire oxide layer. A trapping model which neglects positron diffusion effects was applied to the dependence of the line shape parameter S on incident positron energy.

Journal ArticleDOI
TL;DR: Line strengths and broadening coefficients for formaldehyde (H(2)CO) near 3.5 microm were measured at room temperature using a tunable IR diode laser because of the extremely narrow linewidth of the laser.
Abstract: Line strengths and broadening coefficients for formaldehyde (H2CO) near 3.5 μm were measured at room temperature using a tunable IR diode laser. Because of the extremely narrow linewidth of the laser (≈10−3 cm−1), the transitions were recorded at a resolution limited only by collision and Doppler broadening. The spectral parameters were determined from Voigt line shape fits to R and Q branch rotational–vibrational transitions of the ν5 band between 2867 and 2881 cm−1. Line strength measurements were made on both pure and dilute samples H2CO. Pressure broadening of H2CO lines by N2 was measured in mixtures containing of 0.8–1.2% H2CO.

Journal ArticleDOI
TL;DR: Positron annihilation measurements in the high Tc superconductor YBa2Cu3O6+χ have been performed and the S parameter decreases with temperature in two steps.

Journal ArticleDOI
TL;DR: This in vitro study identified several hemodynamic and technical factors that affect the CW Doppler spectrum; however, in the clinical setting, their influence on quantitative measurements of the extent of spectral broadening likely can be minimized by a skilled technologist who uses a standardized technique.
Abstract: Spectral analysis of continuous wave (CW) Doppler signals is used for the diagnosis of carotid arterial disease. Previous clinical and in vitro studies have documented that the peak Doppler frequency is increased in recordings made directly over a stenosis and that spectral broadening is observed beyond a stenosis in the region of disturbed flow. However, certain hemodynamic and technical factors can effect the Doppler spectrum and in particular cause spectral broadening although they are not related to the severity of the arterial stenosis. In this in vitro study, Doppler spectra were quantified by (1) measurements of the peak, mean and mode frequencies, and (2) measurements that quantify changes in the shape of the spectra and thus can potentially detect the presence of spectral broadening. The latter measurements included the spectral broadening index (SBI), coefficient of variation (CV), coefficient of skewedness (CS), and coefficient of kurtosis (CK). Using straight tubes without a bifurcation in a steady flow model, we found that the peak frequency and the extent of spectral broadening were dependent upon the severity of the stenosis, the relation of the recording site to the stenosis or bulb, and the flow rate. Comparison of the severity of Doppler spectral broadening from bulb and stenosis recordings allowed us to conclude that any observed changes in spectral broadening measurements are probably due to a significant stenosis and not to the presence of a normal bulb. If the tube is not completely insonated by the CW Doppler beam, an error of between 4 and 35% can be read in the spectral broadening measurements. The peak frequency, mean frequency, and SBI are not altered significantly by the automatic gain control or dynamic range and noise level settings usually chosen by the spectrum analyzer. Because of the variability of individual Doppler spectra, one should be cautious about deriving quantitative data from one individual spectrum. The results of quantitative analysis of the amplitude spectrum are different from the power spectrum. In conclusion, this in vitro study identified several hemodynamic and technical factors that affect the CW Doppler spectrum; however, in the clinical setting, their influence on quantitative measurements of the extent of spectral broadening likely can be minimized by a skilled technologist who uses a standardized technique.

Journal ArticleDOI
TL;DR: In this paper, active beam scattering method was applied to ion temperature measurements in JT-60 plasmas and the ion temperature found was in reasonable agreement with that obtained from Doppler broadening of the Ti XXI and Ti XXII resonance lines in the temperature range of 1.5 to 10 keV.
Abstract: The active beam scattering method was applied to ion temperature measurements in JT-60 plasmas. The ion temperature found was in reasonable agreement with that obtained from Doppler broadening of the Ti XXI and Ti XXII resonance lines in the temperature range of 1.5 to 10 keV. With the help of the scattering system, the central ion temperature of JT-60 plasmas during 40 keV and 70-75 keV NBI heating was measured. Higher ion temperature was obtained during 70 to 75 keV than during 40 keV NBI heating. These data and a possible explanation are presented. A numerical simulation of this diagnostic indicates that the ion temperature as deduced from the diagnostic is almost equal to the bulk temperature when the ratio of high energy ion component to the total ion stored energy is less than 0.3.

Journal ArticleDOI
TL;DR: The positron annihilation technique has been used for studying the high Tc-superconductor YBa2Cu3O7-x as discussed by the authors, and the positron lifetimes of the normal state and of the superconducting state have been measured.
Abstract: The positron annihilation technique has been used for studying the high-Tc-superconductor YBa2Cu3O7-x. The Doppler broadening lineshape parameter as a function of temperature between 75 and 300 K, and the positron lifetimes of the normal state and of the superconducting state have been measured. A sharp negative anomaly in the S-parameter was observed near the superconducting transition temperature. In addition, it was found that the S-parameter and mean lifetime decrease below the transition temperature Tc. These phenomena vanish for the samples annealed in vacuum at 800 degrees C. It is suggested that high-Tc superconductivity in the new oxide is probably accompanied by an adjustment in the positions of the oxygen vacancies and the occurrence of 'valence pairs', i.e. an enhancement of the covalent character of the electrons after the superconducting transition.

Journal ArticleDOI
TL;DR: In this article, the profile of the burnt zero-phonon hole, as well as the time dependence of the hole depth, has been measured at 2 K for rhodamine 640 in a polyvinyl alcohol film by means of a highly sensitive spatial-modulation technique.

Journal ArticleDOI
TL;DR: The effect of level broadening on the steady part of the magnetic moment and specific heat is calculated by deriving an analytic expression for the free energy of a two-dimensional electron gas in a uniform magnetic field with an arbitrary Landau-level broadening and at a finite temperature.
Abstract: We calculate the effect of level broadening on the steady part of the magnetic moment and specific heat by deriving an analytic expression for the free energy of a two-dimensional electron gas in a uniform magnetic field, with an arbitrary Landau-level broadening and at a finite temperature. Measurements of these effects may provide a new way for gaining more information about the magnetic-field and temperature dependences of the Landau-level width. This in turn may lead to information about the density of states. In the particular case of Gaussian broadening, the broadening correction to the steady magnetic moment is as large as the steady magnetic moment itself.