Showing papers on "Doppler broadening published in 1977"
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01 Apr 1977
TL;DR: In this paper, the theory of Resonant Interaction of a Laser Field and Gas was introduced and Narrow Saturation Resonances on Doppler-Broadened Transition was discussed.
Abstract: 1. Introduction.- 2. Elements of the Theory of Resonant Interaction of a Laser Field and Gas.- 3. Narrow Saturation Resonances on Doppler-Broadened Transition.- 4. Narrow Resonances of Two-Photon Transitions Without Doppler Broadening.- 5. Nonlinear Resonances on Coupled Doppler-Broadened Transitions.- 6. Narrow Nonlinear Resonances in Spectroscopy.- 7. Nonlinear Atomic Laser Spectroscopy.- 8. Nonlinear Molecular Laser Spectroscopy.- 9. Nonlinear Narrow Resonances in Quantum Electronics.- 10. Narrow Nonlinear Resonances in Experimental Physics.- 11. Conclusion.- Author Index.
396 citations
TL;DR: In this paper, a review describes atomic transitions where two or more photons are simultaneously absorbed by an atom or a molecule (without any intermediate resonant level) and the possibilities of these transitions for numerous high-resolution spectroscopic studies.
Abstract: The review describes atomic transitions where two or more photons are simultaneously absorbed by an atom or a molecule (without any intermediate resonant level). The authors show theoretically and experimentally the possibilities of these transitions for numerous high-resolution spectroscopic studies. The Doppler broadening is suppressed in two-photon transitions if the atoms are irradiated by two laser waves travelling in opposite directions, because the Doppler shift in one wave cancels that in the other. A generalization is made for multiphotonic transitions. A typical experimental set-up with a CW dye laser is described in detail, but the possibilities of other light sources are also discussed.
154 citations
TL;DR: It is shown that scatterers moving in the near field of the sound beam generated by a single transducers ultrasound Doppler system produce a spectrum whose breadth is primarily determined by the range of angles over which backscattered ultrasound is received by the transducer.
Abstract: The bandwidth of the output spectrum of blood flow meters may prove of value in estimating flow parameters such as the degree of turbulence. It is therefore important to determine the various factors which affect this bandwidth. It is shown that scatterers moving in the near field of the sound beam generated by a single transducer ultrasound Doppler system produce a spectrum whose breadth is primarily determined by the range of angles over which backscattered ultrasound is received by the transducer. An empirical method of calculating the bandwidth of the output spectrum is described, and the results are compared with direct Doppler measurements. Since the spectrum broadening depends on the angle between the target path and the ultrasound beam, it is suggested that the phenomenon may be usable to provide an independent measure of this angle.
61 citations
TL;DR: In this article, the dynamic and spectral behavior of injection lasers, the methods of high bit rate modulation and the improvement of the high bit-rate modulation capability by coupling two lasers are discussed.
Abstract: GaAs double heterostructure semiconductor injection lasers which now exhibit more than 25000 h cw room temperature lifetime are of great interest for future use as directly modulated transmitters for high bit-rate fiber optical communications. The effects limiting this application are modulation distortions, spectral width and additional spectral broadening in the case of modulation and spontaneous fluctuations of the output power. The dynamic and spectral behavior of injection lasers, the methods of high bit-rate modulation and the improvement of the high bit-rate modulation capability by coupling two lasers are discussed.
38 citations
TL;DR: In this article, a Doppler broadening of various ion lines is used to measure ion temperatures in the ATC tokamak by means of DoP broadening.
Abstract: Measurements of ion temperatures in the ATC tokamak by means of Doppler broadening of various ion lines are described, and typical results presented for the various auxiliary heating experiments: compression, neutral beam, lower hybrid and ion cyclotron frequency heating. Radial resolution of the temperature measurements is achieved by utilizing spectrum lines of ions of different ionization potentials: O VII λ 1623 A, C V λ 2271 A and C IV λ 1548 A, which are emitted from regions of different electron temperature. Measurement at a given radial location is performed as a function of time by repeated scanning of the line contour in times 1.5–3.0 ms. The results indicate variations of heating efficiency with location and with power input level.
32 citations
TL;DR: In this article, the authors investigated the broadening and shift of the sodium 3S-4D and threeS-5S two-photon transitions without Doppler broadening by collisions with the noble gases.
Abstract: Investigates experimentally the broadening and the shift of the sodium 3S-4D and 3S-5S two-photon transitions without Doppler broadening by collisions with the noble gases. The broadening cross section is larger for the 3S-5S transition than for the 3S-4D transition. The experimental values for the 3S-5S transition are compared with semiclassical calculations using the van der Waals potential and the potentials calculated by Pascale and Vandeplanque (1974).
29 citations
TL;DR: In this article, the angle dependence of the Lorentz and polarization factors is corrected before the deconvolution procedure if the spectral broadening dominates in the instrumental line profile, but after the deconvolution procedure if instrumental factors dominate the line profile.
Abstract: In accurate line profile analysis, corrections have to be made for the angle dependence of the Lorentz and polarization factors. These corrections should be performed before the deconvolution procedure if the spectral broadening dominates in the instrumental line profile, but after the deconvolution procedure if instrumental factors dominate the instrumental line profile. The different formulae to be applied for the Lorentz-polarization factor are indicated. The correction for the angle dependence of the structure factor should always be performed after the deconvolution procedure.
27 citations
TL;DR: In this paper, a broad iron line feature is observed in the normal high state spectrum of Her X-1 and the line equivalent width is given along with its fullwidth-half-maximum energy.
Abstract: The X-ray spectrum of Hercules X-1 was observed in the energy range 2-24 keV from August 29 to September 3, 1975. A broad iron line feature is observed in the normal high state spectrum. The line equivalent width is given along with its full-width-half-maximum energy. Iron line fluorescence from an opaque, cool shell of material at the Alfven surface provides the necessary luminosity in this feature. The line energy width can be due to Doppler broadening if the shell is forced to corotate with the pulsar at a radius 800 million cm. Implications of this model regarding physical conditions near Her X-1 are discussed.
23 citations
TL;DR: In this paper, the correlation function of light scattered from dilute solutions of large molecular weight polystyrene has been measured using a photon-counting digital autocorrelator.
20 citations
01 Jan 1977
TL;DR: In this paper, the turbulent structure of small jet diffusion flames was investigated using a variety of measuring techniques, each being capable of time resolution, including laser Doppler anemometry, quantitative Schlieren, cross-beam correlation techniques and thermocouple probes.
Abstract: This paper describes an investigation into the turbulent structure of small jet diffusion flames, using a variety of measuring techniques, each being capable of time resolution. These include laser Doppler anemometry, quantitative Schlieren, cross-beam correlation techniques and thermocouple probes. Spectra are reported. The Schlieren spectra display both high and low frequency structures. In the flames the high frequency peaks, which are associated with vortex shedding, are found to be significantly different from those observed in the equivalent cold jets. Both the velocity and Schlieren spectra indicate that heat release has considerable influence upon the dissipation of the higher wave number turbulence fluctuation. The Schlieren spectra are dominated by a low frequency phenomenon, which appears to be of a quasi-laminar nature. This structure is found to be a well defined oscillation in the laminar flames; although undergoing a spectral broadening, it persists in the higher velocity turbulent flames investigated. Comparison of these spectra with far field noise spectra shows significant differences, although again indicating a dominance of low frequency structure.
20 citations
TL;DR: In this paper, a theoretical consideration is made of the thermal broadening and shift of the impurity energy levels in crystals doped with TR3+ ions using the Hamiltonian of electron-phonon interaction containing linear terms in the lattice variables.
Abstract: A theoretical consideration is made of the thermal broadening and shift of the impurity energy levels in crystals doped with TR3+ ions using the Hamiltonian of electron-phonon interaction containing linear terms in the lattice variables. In the method developed for the calculation of these effects the real phonon density distribution is used for the host crystal. The information about this distribution is obtained from the spectrum of vibrational satellites of zero-phonon lines. The calculations are carried out for the thermal broadening and the shift of some lines in the 3/2 4I11/2 luminescence band of the Nd3+ ion in an YAIO3 host crystal.
TL;DR: In this paper, the spatial mean ocean wind speeds were obtained using Doppler spectra resolved to 0.08 Hz from high-resolution HF skywave-radar backscatter measurements of the ocean surface.
Abstract: Remote measurements of the spatial mean ocean wind speeds were obtained using Doppler spectra resolved to 0.08 Hz from high-resolution HF skywave-radar backscatter measurements of the ocean surface. A standard deviation of 2.4 m/s resulted from the correlation of observed winds over the ocean and the broadening of the Doppler spectra in the vicinity of the higher first-order Bragg line. This broadening, for Doppler spectra unperturbed by the ionospheric propagation, is proportional to the increase in power caused by higher order hydrodynamic and electromagnetic effects in the vicinity of the Bragg line and inversely proportional to the square root of the radio frequency. A lower bound on the measure of wind speed was established at 5 m/s by the low resolution spectral processing and low second-order power. An upper limit is suggested by the steep slope in the region of the sea backscatter spectrum outside the square root of two times the first-order Bragg line Doppler.
TL;DR: The measured shape of the collision-broadened resonance lines of the light element lithium is found to deviate significantly from the expected Voigt shape when broadened by heavy gases as mentioned in this paper.
Abstract: The measured shape of the collision-broadened resonance lines of the light element lithium are found to deviate significantly from the expected Voigt shape when broadened by heavy gases. The observed shape is in excellent agreement with that recently computed by Ward, Cooper and Smith (1974), who have taken full account of the distortion of the profile expected from the correlations between the Doppler and collision-broadening process.
TL;DR: In this paper, a singlemode dye-laser scattering in the near wings of the D1 and D2 resonance lines is used for determining sodium densities in nonhomogeneous optically thick plasmas, where the laser frequency is detuned far enough from (the intermediate) resonance to make the plasma optically thin for the laser beam(s) and for the directly scattered light.
Abstract: Two possible techniques for determining sodium densities in nonhomogeneous optically thick plasmas are investigated. The first one is single‐mode dye‐laser scattering in the near wings of the sodium D1 and D2 resonance lines. The second technique is near‐resonant two‐photon absorption with two counterpropagating single‐mode dye‐laser beams and detection of the fluorescence. In both cases, the laser frequency(ies) is (are) detuned far enough from (the intermediate) resonance to make the plasma optically thin for the laser beam(s) and for the directly scattered light, hence for the one‐step two‐quantum transitions. In the scattering experiment, the polarization properties of the scattered light are used for discrimination against the stepwise absorption‐reemission (the collision‐induced fluorescence). In the two‐photon absorption experiment, the residual Doppler broadening is small enough to make a clear distinction between the direct two‐quantum and the collision‐induced stepwise one‐quantum transitions. I...
TL;DR: In this article, the authors generalized the treatment of resonance-line radiation from a spherical, laser-heated plasma by including the effects of radiative and collisional line broadening in representing the line-emission and absorption profiles by a Voigt function.
Abstract: We have generalized our treatment of resonance-line radiation from a spherical, laser-heated plasma by including the effects of radiative and collisional line broadening in representing the line-emission and absorption profiles by a Voigt function. We find that the emitted profiles are broadened by factors of five or more, depending on the magnitude of the damping constant. It is also shown that the Al(XIII) to Al(XII) line ratios are seriously affected by the different escape probabilities associated with Doppler and Voigt profiles. We also find that plasma cooling via resonance-line radiation is accelerated relative to that calculated with a pure Doppler profile, and that use of the Voigt profile decreases the density of excited states relative to the Doppler values. These phenomena are analyzed in terms of the differing profile shapes and widths.
TL;DR: In this article, the velocities of helium ions and neutrals are derived from Doppler shifted spectral lines He II 4686 Å and He I 5876 Å respectively.
Abstract: Abstract The velocities of helium ions and neutrals are derived from Doppler shifted spectral lines He II 4686 Å and He I 5876 Å respectively. The ion velocity proves to be in accordance with the speed of rotating spokes which are usually observed in the build-up phase of rotating plasmas. It is demonstrated that the spoke velocity represents the plasma mass motion. Braking of plasma motion and acceleration of the neutrals to a value near Alfvén's critical velocity occurs within 10 μs.
TL;DR: In this paper, the authors considered the Doppler-broadened absorption by two-level molecules of a gas from a weak traveling electromagnetic plane wave in the presence of an oppositely traveling strong plane wave at the same frequency.
Abstract: We consider in this paper the Doppler-broadened absorption by two-level molecules of a gas from a weak traveling electromagnetic plane wave in the presence of an oppositely traveling strong plane wave at the same frequency. Here the absorption spectrum exhibits a dip that broadens and deepens as the gas is increasingly saturated by the strong wave. This saturation effect has been employed in the recent experiments on the fine structure of atomic hydrogen performed by H\"ansch, Shahin, and Schawlow (HSS). The form, linewidth, and strength of saturation dips in the fine-structure lines are studied for experimental parameters appropriate to the hydrogen experiment. In addition, saturation line-shape curves are calculated for experimental situations in which the strengths of the stronger field give rise to stronger or weaker saturation of the gas medium and varying degrees of Doppler broadening exist. The calculation of shape of the saturation dip and absorption curves for a Doppler-broadened gas of two-level atoms is made exactly; in effect, the strong field is treated as arbitrarily strong by avoiding a perturbation-theory treatment in favor of the exact solutions for a driven two-level system. The general behavior found is in accord with intuition and experimental observations by HSS. There is an optimum saturation power which gives a prominent dip and beyond which the dip suffers "power broadening."
TL;DR: In this paper, the spectrum of scattered radiation from atoms in a perturber gas was studied and expressions for the profile of the Raman scattering and of the fluorescence were derived.
Abstract: We study the spectrum of scattered radiation from atoms in a perturber gas. The incident radiation is in near-resonance with a transition to a single intermediate state, and the final state may differ from the initial state. Effects of the degeneracy of the states are not considered. We derive expressions for the profile of the Raman scattering and of the fluorescence. The additional effects of Doppler broadening are studied in several simple cases.
TL;DR: In this paper, the expansion velocities of laser-produced plasmas were determined from the shapes of spectral lines of highly ionized iron emitted in the extreme ultraviolet, and the relative time-averaged ion abundances of Fe XVIII, Fe XIX, Fe XX, and Fe XXI were estimated for three different spectra.
Abstract: The expansion of laser‐produced plasma is determined from the shapes of spectral lines of highly ionized iron emitted in the extreme ultraviolet. The plasmas were produced by focusing the pulse from a Nd : glass laser onto solid planar targets, and spectra were recorded with a high‐resolution grazing incidence spectrograph. From the Doppler broadening of lines of Fe XX and Fe XXI, expansion velocities of ∼830 km s−1 were determined. The relative time‐averaged ion abundances of Fe XVIII, Fe XIX, Fe XX, and Fe XXI are estimated for three different spectra. The abundances do not differ by more than a factor of 4 for any of the spectra.
TL;DR: In this paper, the ion temperature in the Tokamak LT-3 has been deduced from measurements of the thermal Doppler broadening of oxygen impurity line emission from the hydrogen plasma.
Abstract: The ion temperature in the Tokamak LT-3 has been deduced from measurements of the thermal Doppler broadening of oxygen impurity line emission from the hydrogen plasma. The profiles of lines in the UV region of the spectrum were analysed with a polychromator which measures simultaneously 7 contiguous spectral bands separated by 0.25 AA in the wavelength. With this instrument, ion temperatures as low as 10 eV could be measured reliably. In stable discharges, which occur in LT-3 only for a sufficiently high q-value at the plasma column boundary, the central ion temperature rise to a maximum of about 30 eV after 4 ms from the initiation of the discharge. The ion energy confinement time at the centre of the discharge reaches a maximum value of about 400 mu s.
TL;DR: A method for eliminating the Doppler effect by the counterpropagating-beam two-photon technique is described in this article, with a focus on gas-phase molecular electronic-state spectroscopy.
Abstract: A method is described for eliminating the Doppler effect by the counterpropagating-beam two-photon technique. Emphasis is placed on gas-phase molecular electronic-state spectroscopy. Past accomplishments with this method are summarized and applications of the method are discussed.
TL;DR: In this article, the temperature dependence of positron annihilation in copper between 93 and 665K was investigated by simultaneous measurements of the positron lifetime and Doppler broadening of the annihilation spectrum.
Abstract: The temperature dependence of positron annihilation in copper between 93 and 665K has been investigated by simultaneous measurements of positron lifetime and Doppler broadening of the annihilation spectrum. The lifetime and spectrum shape were found to vary linearly with temperature, thus giving no indication of the existence of positron self-trapping in copper.
TL;DR: In this paper, the positron mean life and the Doppler broadening of the annihilation line were measured in tin from −196°C to 220°C with a small increase with temperature.
01 Jan 1977
TL;DR: Positron annihilation is a sensitive technique for probing defects in metals and it has recently been shown to be a valuable tool for the study of radiation damage as mentioned in this paper, and the role of positron techniques in characterizing complex defect structures resulting from high-temperature neutron irradiation is reviewed and the possible utility of POSron annihilation as a nondestructive monitor of property changes is pointed out.
Abstract: Positron annihilation is a sensitive technique for probing defects in metals and it has recently been shown to be a valuable tool for the study of radiation damage. After an introduction to the three basic experimental methods (angular correlation, Doppler broadening, and lifetime measurements), the interaction of positrons with lattice defects is reviewed. Results for the annealing of damage after low temperature irradiation are used to show that positron annihilation has provided new information on annealing kinetics. The role of positron techniques in characterizing complex defect structures resulting from high-temperature neutron irradiation is reviewed and the possible utility of positron annihilation as a nondestructive monitor of property changes is pointed out.
TL;DR: In this paper, an analytical solution for the excitation of a 3-level atom by two laser fields of different propagating in opposite directions is presented for the rotating wave approximation, where the maximum population of the upper level is achieved when the laser powers are chosen to give the same power broadening for both transitions.
01 Jan 1977
TL;DR: In this paper, it has been shown that the radiative recoil-induced doublets in the three main hyperfine components of methane at 3.39 pm can be resolved using an external absorption cell with a 30 cm aperture.
Abstract: Provided one has been able to develop/acquire frequency and intensity stabilized sources of coherent radiation, there remain two main problems in the pursuit of narrow lines: transit time broadening and Doppler broadening. The first-order Doppler effect may be essentially eliminated by various techniques: saturated absorption, two-photon spectroscopy, highly collimated beams, ... Transit time (interaction time) broadening is more difficult to eliminate. Still, it has recently proved possible to resolve the radiative recoil-induced doublets in the three main hyperfine components of methane at 3.39 pm. This high resolution (2 parts in 1011), derived from an external absorption cell with a 30 cm aperture, nevertheless remained 2 orders of magnitude removed from the natural lifetime line width. Larger cells and associated optics being cumbersome, one is induced to find alternative schemes to reduce transit time broadening and so approach natural line width resolution.
TL;DR: In this article, the spatial mean ocean wind speeds were obtained using Doppler spectra resolved to 0.08 Hz from high-resolution HF skywave-radar backscatter measurements of the ocean surface.
Abstract: Remote measurements of the spatial mean ocean wind speeds were obtained using Doppler spectra resolved to 0.08 Hz from high-resolution HF skywave-radar backscatter measurements of the ocean surface. A standard deviation of 2.4 m/s resulted from the correlation of observed winds over the ocean and the broadening of the Doppler spectra in the vicinity of the higher first-order Bragg line. This broadening, for Doppler spectra unperturbed by the ionospheric propagation, is proportional to the increase in power caused by higher order hydrodynamic and electromagnetic effects in the vicinity of the Bragg line and inversely proportional to the square root of the radio frequency. A lower bound on the measure of wind speed was established at 5 m/s by the low resolution spectral processing and low second-order power. An upper limit is suggested by the steep slope in the region of the sea backscatter spectrum outside the square root of two times the first-order Bragg line Doppler.
TL;DR: In this paper, the theory of the Forrester effect was reexamined in both classical and quantum terms, and it was shown that temporal coherence can arise from the interference of fields produced either by single atoms or by pairs of atoms.
Abstract: The theory of the Forrester effect is reexamined in both classical and quantum terms. We show that temporal coherence (light beating) can arise from the interference of fields produced either by single atoms or by pairs of atoms. The singles terms, which dominate for a collisionless source with low intensity, give a light-beating signal-to-noise ratio of order unity, independent of the intensity and wavelength. This signal is also unaffected by Doppler broadening. The doubles terms, originally analyzed by Forrester, give a signal-to-noise ratio proportional to the intensity and to the square of the wavelength, and subject to Doppler broadening. Our results suggest the possibility of a new type of rf and microwave spectroscopy for excited atoms.
TL;DR: In this paper, the authors interpreted the Doppler broadening due to fast neutral particles produced by the charge transfer with hot ions in the plasma of the neutral particle density of ∼10 14 cm -3 comparable with the plasma density.
Abstract: Spectral line profiles of He I 4922 A line (2 1 P-4 1 D, 1 F) and 4471 A line (2 3 P-4 3 D, 3 F) with their forbidden components from a small linear theta pinch plasma have been measured and the plasma satellites have been observed on the wing of the line profiles. The observed profiles have broadened wings, and they are interpreted as the Doppler broadening due to fast neutral particles produced by the charge transfer with hot ions in the plasma of the neutral particle density of ∼10 14 cm -3 comparable with the plasma density. The low and high frequency fluctuating fields with the average strength of several kV/cm are deduced from the plasma satellites in the observed profiles.
TL;DR: In this paper, the authors measured the Doppler broadening in H β due to the Coulomb repulsion energy in the break-up of fast hydrogenic molecular ions passing through thin carbon foils.