Showing papers on "Doppler broadening published in 1968"
TL;DR: Helium I line profiles including forbidden component, discussing electron and ion Stark broadening and thermal Doppler broadening were discussed in this article, where the authors also discussed the electron broadening.
Abstract: Helium I line profiles including forbidden component, discussing electron and ion Stark broadening and thermal Doppler broadening
85 citations
TL;DR: In this article, the Doppler shifts in the frequency of laser light scattered by small particles in the water were measured using an optical hetrodyne technique to measure the shift in frequencies.
Abstract: The local mean values and fluctuations of the velocity of water in turbulent flow through a tube have been determined from the Doppler shifts in the frequency of laser light scattered by small particles in the water. An optical hetrodyne technique was used to measure the shift in frequencies. The limited lifetime of the Doppler shifted signals, due to the finite time of passage of the scattering particles through the laser beam, causes broadening of the frequency spectra representing the fluctuations in turbulent velocity. This broadening, which is analogous to the Doppler radar ambiguity, was investigated with laminar flow and was allowed for in interpreting the spectra observed with turbulent flow. The optics were chosen so that the coherence limits were at all times greater than the beam diameter and did not further shorten the lifetimes of the Doppler signals. The root mean squares of the fluctuations in velocity, calculated from the observed spectra, are in agreement with corresponding data obtained by hot wire anemometry.
72 citations
TL;DR: Spectral lines combined Doppler and collision effect studied by statistical correlation function for time varying amplitude of classical oscillators as mentioned in this paper, and the correlation function was used to measure the collision effect.
Abstract: Spectral lines combined Doppler and collision effect studied by statistical correlation function for time varying amplitude of classical oscillators
68 citations
TL;DR: The use of low pressures and a high-resolution spectrometer for the measurement of the absolute line strengths of gases in the near infrared is tested on the first overtone band of carbon monoxide.
Abstract: The use of low pressures and a high‐resolution spectrometer for the measurement of the absolute line strengths of gases in the near infrared is tested on the first overtone band of carbon monoxide. Measurements are made at pressures from 100 to 500 μ Hg, where the line profile has nearly a pure Doppler contour, and at pressures 2 to 7 cm Hg, where the effects of Doppler and collision broadening are both important. It is found that both wing and base corrections must be made in higher‐pressure measurements, and these corrections are given for lines with combined Doppler and collision‐broadened profiles. It is found that the use of the Doppler profile offers significant advantages for the accurate determination of line strengths, and a discussion of these advantages are included. It is shown that within the accuracy of the measurements, the true line profile at pressures from 100 to 500 μ Hg cannot be distinguished from the assumed Doppler profile. The band strength of the first overtone band of CO is calculated from the measured line strengths, and the best value obtained at a temperature of 273°K is 2.06 ± 0.07 cm− 2·atm− 1.
58 citations
TL;DR: In this article, a high-intensity beam of 2 keV neutrons having a full width at half maximum of 800 eV has been produced by placing a scandium filter in the Materials Testing Reactor.
28 citations
TL;DR: In this paper, the formation of spectral lines by non-coherent scattering with a frequencyindependent source function is predicted theoretically for a plane-parallel medium of finite optical thickness, and the problem is reduced, as in earlier investigations of monochromatic scattering, to one of determining two standard functions X and Y or, in the case of a semi-infinite medium, a single function H. Analytic approximations of these functions are discussed and representative numerical calculations are included.
Abstract: The formation of spectral lines by noncoherent scattering with a frequency-independent source function is predicted theoretically for a plane-parallel medium of finite optical thickness. The problem is reduced, as in earlier investigations of monochromatic scattering, to one of determining two standard functions X and Y or, in the case of a semi-infinite medium, a single function H. Analytic approximations of these functions are discussed and representative numerical calculations are included. Particular attention is devoted to Doppler broadening. Comparisons of both analytic and tabular results are made with purely numerical studies of particular cases.
27 citations
TL;DR: In this article, the nonlinear properties of a gas laser amplifier subject to an axial magnetic field, operating with two optical-frequency signals of arbitrary polarization, were analyzed using classical fields and the density-matrix formalism.
Abstract: Using classical fields and the density-matrix formalism, we analyze the nonlinear characteristics of a gas laser amplifier subject to an axial magnetic field, operating with two optical-frequency signals of arbitrary polarization. Perturbational solutions, valid for relatively weak intensities, are obtained which describe the saturation interaction of the signals and the generation of combination tones. An arbitrary amount of Doppler broadening is considered throughout. The simple $J=1\ensuremath{\rightarrow}J=0$ model is found convenient to describe the physical processes taking place. In general, however, the interactions are found to depend on the $J$ values of the levels. We find that only saturation and no combination-tone generation occurs for two opposite circularly polarized signals, while both effects are, in general, present for two linearly or elliptically polarized fields. The limiting case of zero magnetic field is examined separately. It is also found that in many cases the medium is made effectively anisotropic by the nonlinear interactions. Applications to measurements of atomic parameters such as $J$ values, $g$ values, and lifetimes are discussed.
24 citations
TL;DR: In this article, a simple and accurate method of computing Voigt functions is presented, and the method is suggested as a possible means of computing related functions, which can be used as a solution to the problem of computing the Voigts.
Abstract: A simple and accurate method of computing Voigt functions is presented. The method is suggested as a possible means of computing related functions.
21 citations
TL;DR: In this paper, the contribution of multiple transfer of excitation and of two-body scattering are calculated separately, and the velocity dependence of the width parameter is investigated in some detail; their results differ considerably from the existing results because they have included higher-order contributions.
Abstract: The line-shape function is expressed in terms of three boundary functions related to the two-particle Green's function. The transverse as well as the longitudinal interaction among atoms is considered, using the photon propagator approach. The broadening of one of the radiative states through the resonance interaction with the ground state is considered in detail. The contributions of multiple transfer of excitation and of two-body scattering are calculated separately. Several validity conditions are also obtained which clarify the approximations in the existing results. The velocity dependence of the width parameter is investigated in some detail; our results differ considerably from the existing results because we have included higher-order contributions. The extreme low-density region [where (collision width) \ensuremath{\sim} (natural width)] is also considered; the linewidth is found to be nonlinear in the number density. The additional contribution of the coupling between the radiative states is also calculated in a special case.
20 citations
TL;DR: In this article, the authors explain the nonlinear dielectric response of anisotropic molecules in the incident optical beam with respect to the frequency ω 1 and ω 2.
Abstract: Spectral broadening by the nonlinear dielectric response of anisotropic molecules has been observed and explained by Bloembergen and Lallemand.(1) Any two frequencies, say ω1 and ω2, present in the incident optical beam exert a torque on the molecules at a frequency (ω1-ω2). The resultant oscillation of the average molecular orientation causes a modulation of the dielectric constant at ω1-ω2.
17 citations
TL;DR: In this article, a simple ray analysis is used to derive expressions for the angular spread and spectral broadening of coherent radio signals on traversing the turbulent interplanetary medium, when the anisotropy and radial gradient of the turbulence and the large-scale motions of the medium (solar wind) are important.
Abstract: A simple ray analysis is used to derive expressions for the angular spread and spectral broadening of coherent radio signals on traversing the turbulent interplanetary medium, when the anisotropy and radial gradient of the turbulence and the large-scale motions of the medium (solar wind) are important. The resulting expressions are used to interpret observations, reported in the literature, of the angular broadening of natural radio sources and of the spectral broadening of Mariner 4 during superior conjunction. In the region 10–100 solar radii our results are consistent with a coronal electron concentration behaving as r−2 and a statistical correlation length which during solar minimum does not vary with r but which tends to increase linearly with r near solar maximum, indicating that the interplanetary plasma tends to develop a radial filamentary structure during solar maximum; we find no necessity to invoke nonradial outflow to explain the observations. In the region 3–6 solar radii the data imply a²/b ∼ r³, where a is the correlation length in the radial direction and b is the correlation length in the transverse direction. We point out that this behavior can result if both the transverse correlation length and the anisotropy ratio, a/b, increase linearly with r in that region.
TL;DR: In this article, the spectral distribution of the output from a CW laser oscillator employing an inhomogeneously broadened transition with a finite cross-relaxatian rate is discussed.
Abstract: The spectral distribution of the output from a CW laser oscillator employing an inhomogeneously broadened transition with a finite cross-relaxatian rate is discussed. A theory is presented that describes the spectral broadening and the inversion distribution variations introduced by the finite cross-relaxation rate. It is found that the criterion that must be satisfied by the ratio of the cross-relaxation rate to the stimulated emission rate, in order that the spectrum reduce to its homogeneously broadened limit, is much more stringent than the amplifier "no hole-burning" condition. The average spectral envelope is described analytically. However, it is found that the self-consistent solution for the spectral distribution exhibits important structure within these average bounds. Computer solutions of the model equations are given for the Nd: glass and the 3.51-μ xenon lasers. These solutions are compared with experimentally observed spectral distributions and it is found that the dominant structure patterns are correctly described. For example, the solution for Nd:glass is composed of a series of sharp intense bands separated by weaker broad bands. This banding is observed in the time resolved spectra of the laser output. The width of these sharp bands is determined by higher order effects and may be the limiting width in producing the 3 ps pulses occurring during mode-locked operation. The xenon laser spectrum is composed of a very sharp central peak and several broader lobes.
TL;DR: In this article, theta-pinch device of low stored energy, constructed to provide a convenient spectroscopic source, has produced an interesting and useful plasma, and the discharge tube has an i.d. of 15 cm and the coil is 32 cm long.
Abstract: A theta‐pinch device of low stored energy, constructed to provide a convenient spectroscopic source, has produced an interesting and useful plasma. The discharge tube has an i.d. of 15 cm and the coil is 32 cm long. The main bank energy is 9 kJ at 40 kV, and the current rings with a 7.5 μsec period. Plasma conditions have been investigated for a filling gas pressure of 12 mTorr H2 or D2 and an antiparallel bias field of 500 G using light scattering, time‐ and space‐resolved emission spectroscopy, streak photography, and neutron emission. These reveal that following the initial compression, the plasma forms a stable cylinder about 4.5 cm in diameter which persists for about 1.5 μsec. The maximum electron temperature, determined by light scattering, is about 260 eV. Absolute continuum emission and light‐scattering measurements show the average electron density to be between 3 and 4×1015 cm−3. The temperature of carbon impurity ions is determined to be 1.3 keV from Doppler broadening, and neutron emission wi...
TL;DR: In this article, fast rise pulses from a GaAs electrooptic switch are used to measure the small signal time response to a step of radiation, of a 20 dB, homogeneously broadened CO2, He, N2 laser amplifier.
Abstract: Fast rise pulses from a GaAs electrooptic switch are used to measure the small signal time response to a step of radiation, of a 20 dB, homogeneously broadened CO2, He, N2 laser amplifier. By comparing the observed shape of the time response (rise time ≈ 15 nsec) with theory, the value of T2, the homogeneous relaxation time, and hence the linewidth is obtained as a function of gas pressure. The doppler broadening (59 MHz), pressure broadening (4.67 MHz/Torr) and gas temperature (372°K) are obtained.
TL;DR: The output power of a He-Ne-laser (λ = 633 nm) has been measured as a function of the strength of an axial magnetic field as discussed by the authors.
Abstract: The output power of a He-Ne-laser (λ=633 nm) has been measured as a function of the strength of an axial magnetic field. This function has intensity dips in the regions where the Zeeman splitting is equal to combination frequencies of different modes. These dips have practically the shape of the natural line. The effect enables to measureg-factors, because the Zeeman splitting can be recorded with a resolution, limited only by the natural line width without Doppler broadening.
TL;DR: In this paper, a simplified description of the complex broadening phenomena summarizes all low-density observations, in good approximation, and agrees in its essential qualitative features with the generalized impact theory as recently corrected by Griem for the asymptotic regime, although these recent calculations favor stronger electron impact contributions.
Abstract: The ratio of halfwidth to critical value for the transition between quasi-static and impact domain of electron contributions to linear Stark broadening (according to Unsold) is expected to vary approximately with n4, where n is the upper principal quantum number of the line considered Low-density plasmas generated by a radio frequency arrangement permit the observation of many non-overlapping Balmer lines and thus a drastic variation of the ratio; for identical plasma parameters, access deep into the quasi-static as well as the impact regime of electron broadening is realized to a degree not achieved previously As recently suggested, the observed broadening can be approximated in terms of an effective quasi-static perturber density, which is a universal function of the displacement from the line center expressed in units of the above mentioned critical transition value Normalization of the resultant profiles is maintained Doppler and apparatus broadening contributions are quantitatively taken into account in the analysis of the observations The limitations of the approach are discussed The greatly simplified description of the complex broadening phenomena summarizes all low-density observations, in good approximation, and agrees in its essential qualitative features with the generalized impact theory as recently corrected by Griem for the asymptotic regime, although these recent calculations favor stronger electron impact contributions
TL;DR: In this paper, the integrated absorption for a single line of a uniformly mixed absorber is described and the error introduced by the neglect of Doppler effects, and also the error due to the use of the Curtis-Godson approximation with doppler effect included, are shown.
Abstract: Numerical calculations of the integrated absorption for a single line of a uniformly mixed absorber are described. The error introduced by the neglect of Doppler effects, and also the error due to the use of the Curtis-Godson approximation with Doppler effects included, are shown. The inclusion of Doppler effects is found to improve the Curtis-Godson approximation.
TL;DR: Doppler shift measurements with double wedge technique applied to mass motion of air plasma escaping ends of theta pinch were performed in this paper, where the double wedge was applied to the mass motion.
Abstract: Doppler shift measurements with double wedge technique applied to mass motion of air plasma escaping ends of theta pinch
TL;DR: The mean lifetime of the first excited state of 13C has been determined by the nuclear resonant scattering of bremsstrahlung to be 1.5 ± 0.2 fs.
TL;DR: The theory of the broadening of radiated or backscattered monochromatic waves is investigated in this article, where a simple idealized model is discussed, to show that the classical theory of correlating the frequency spectrum with the line-of-sight velocity distribution is inadequate.
Abstract: The theory of the Doppler broadening of radiated or backscattered monochromatic waves is investigated. A simple idealized model is discussed, to show that the classical theory of correlating the frequency spectrum with the line-of-sight velocity-distribution is inadequate. It is demonstrated that relativistic consideration; yield first-order effects which exist even for low velocities. Consequently, if the spectral and velocity-distribution profiles are compared, the spectral curve shows de-emphasis and preemphasis for lower and higher frequencies, respectively. Experimental evidence supports the theory.
TL;DR: In this paper, it was shown that a sinusoidal phase modulation is responsible for the spectral broadening observed in trapped filaments of laser (and Raman) light, which has been suggested recently by Cheung et al.
Abstract: Evidence is presented indicating that, in some cases at least, a sinusoidal phase modulation is responsible for the spectral broadening observed in trapped filaments of laser (and Raman) light. This kind of modulation has been suggested recently by Cheung et al.
TL;DR: A nonrelativistic formula for calculating the Doppler (kinematic) broadening of the energies of groups of atomic or nuclear particles emitted in two-body collisions is derived in this article.
Patent•
05 Jan 1968
TL;DR: In this article, the authors studied the spectral lines emitted from a plasma in a low pressure helium arc which has an electron temperature of about 105°K and an electron density of about 1014 cm-3.
Abstract: Profiles of Spectral lines emitted from a plasma in a low pressure helium arc which has an electron temperature of about 105°K and an electron density of about 1014 cm-3 have been studied. The results show that the measured profile of HeII 4686 A can be well explained by Doppler broadening if the fine structure is taken into account. The apparent half-widths of HeII 4686 A and HeII 3203 A are shown in a figure as a function of the Doppler half-width of a fine structure component. The profile of HeII 3203 A is mainly formed by Doppler broadening but Stark effect contributes to it by a few percents.
31 Oct 1968
TL;DR: In this article, the authors describe the measurement of inelastic neutron scattering in metallic hydrides, UC and UO{sub 2}, the calculation of their scattering laws, and discusses scattering law applications.
Abstract: This paper describes the measurement of inelastic neutron scattering in metallic hydrides, UC and UO{sub 2}, the calculation of their scattering laws, and discusses scattering law applications. Measurements based on the energy loss method are made at the Rensselaer Linear Accelerator Laboratory. Measurements on ZrH{sub x} (with varying hydrogen concentration), NbH and ThH{sub 2} have been made at room temperature. The ZrH{sub 2} and NbH measurements were repeated at liquid nitrogen temperature. For ZrHx , the variation of optical level width caused by changing sample temperature, momentum transfer and concentration of hydrogen atoms has been studied. NbH data exhibit a doublet at 0.12 and 0.164 eV. This is believed to arise from splitting of the 1-0 transition in the optical band into transverse and longitudinal modes. For metal hydrides the Einstein model is found to be a poor representation of the frequency spectrum. Differential scattering cross-sections have been obtained for UC, using an 8S7o-transmission powder sample, 0.134-eV incident energy and six scattering angles (14 Degree-Sign to 150 Degree-Sign ). A peak at 0.045 eV excitation is observed. UO{sub 2} data were obtained on a depleted powder sample having approximately 95% transmission, for incident energies of 0.341 eV, and scattering angles of 25 Degree-Sign to 150 Degree-Sign . Evidence of inelastic scattering from excitations beyond 0.1 eV, the limit of previous measurements, is observed. Theoretical scattering laws have been calculated for ZrH{sub 2}, UC and UO{sub 2} . The UC scattering data were compared with theoretical results based on a Debye acoustic mode at 0.014 eV and a Gaussian distribution at 0.045 eV . Agreement between theory and experiment is good. For ZrH{sub 2} and UO{sub 2} the frequency spectra reported in the literature were employed. A treatment of proposed multiple scattering corrections is described. The paper also discusses applications of scattering laws. The importance of the experimental and theoretical study of Placzek moments is stressed.We especially emphasize the role of these moments, including the effective temperature, in the study of Doppler broadening of resonances of fissile, fertile and structural materials. This broadening may play a significant role in temperature coefficients of fast reactors. (author)
TL;DR: In this article, the profiles of ionic helium line, 3203 A, from a low-density and high-electron-temperature plasma which was formed in a low pressure arc discharge chamber immersed in a magnetic field are investigated.
Abstract: The profiles of ionic helium line, 3203 A, from a low-density and high-electron-temperature plasma which is formed in a low pressure arc discharge chamber immersed in a magnetic field are investigated. The electron density of the plasma is about 8×10 13 /cm 3 and the electron temperature is about 2×10 5 °K. The red wing of the profile is found to be formed by the Stark broadening of ions and electrons. The electron densities are determined by the intensity of the red wing by using the theory of the Stark broadening of Griem and compared with the results of microwave interferometer and Langmuir probe measurements.
TL;DR: The mutual-indication method for the determination of the neutron resonance parameters σ r and Γ is applied to thin foils, including detailed treatment of Doppler broadening as discussed by the authors.
01 Jan 1968
TL;DR: However, Omholt and others concluded that protons cannot be responsible for producing auroral arcs (Chamberlain, 1961, Chapter 7), and as mentioned in this paper showed that auroras with an arc or band structure are not produced by protons, but by electrons.
Abstract: Vegard (1939) and Gartlein (1950) were among the first to identify the Balmer lines, Hα, Hβ, and Hγ in auroral spectra. The discoveries of the Doppler broadening of the Hα line by Gartlein (1950) and of the Doppler shift of the Hα line by Meinel (1951) marked important epochs in the development of auroral physics; their findings had been taken to be direct evidence to show that solar corpuscles produced auroras after entering the geomagnetic field. For this reason, a considerable effort was made to study the excitation of auroral luminosity by incoming protons. However, Omholt (1959) and others concluded that protons cannot be responsible for producing auroral arcs (Chamberlain, 1961, Chapter 7). Indeed, rocket observations have demonstrated that auroras with an arc or band structure are not produced by protons, but by electrons (cf. McIlwain, 1960; Evans, 1968; Pfister, 1967). Only very recently, however, Romick and Belon (1967a, b), Murcray (1967) and Mozer and Bruston (1967) have presented evidence which suggests that the λ 5577 line may be produced by other processes than a simple excitation of oxygen atoms by secondary electrons.