Showing papers on "Doppler broadening published in 1974"
230 citations
TL;DR: In this paper, the transition of Na atoms is induced by absorption of two photons, one each from two circularly polarized beams traveling in opposite directions through the vapor, derived from a tunable, narrow-band pulsed dye laser.
Abstract: The $3S\ensuremath{-}5S$ transition of Na atoms is induced by absorption of two photons, one each from two circularly polarized beams traveling in opposite directions through the vapor. The beams are derived from a tunable, narrow-band pulsed dye laser. Doppler broadening is absent and the hyperfine structure is resolved. The hyperfine interaction constant ${A}_{5S}$ in the $5S$ state of the ${\mathrm{Na}}^{23}$ atom is determined to be 101\ifmmode\pm\else\textpm\fi{}15 MHz.
217 citations
TL;DR: In this article, the combined effects of radiator-perturber collisions and radiator translational motion in the context of foreign gas broadening of optical transitions in neutral radiators are investigated.
Abstract: An investigation is conducted of the combined effects of radiator-perturber collisions and radiator translational motion in the context of foreign gas broadening of optical transitions in neutral radiators. Questions concerning the speed-dependent collision frequency are considered and aspects of general theory are explored, taking into account the correlation function, the ensemble average, and the kinetic equation formalism. An elementary solution is discussed along with a one-perturber approximation, inverse power law model calculations, and a comparison with the Voigt profile.
183 citations
TL;DR: In this paper, a theory of broadening of He I lines with forbidden components is developed, which takes into account the effects of dynamic ion broadening and is valid at low densities where the forbidden line is reasonably well isolated.
Abstract: A theory of the broadening of He I lines with forbidden components is developed. The theory takes into account the effects of dynamic ion broadening and is valid at low densities where the forbidden line is reasonably well isolated. Good agreement with experiment and with calculations by Lee (1972) was obtained when the theory was applied at a wavelength of 4471 A. Tables of these data are given and are extended into the line wings beyond the extent of previous tabulations. Reasons for agreement with Lee data are discussed in detail. The density level above which the static ion theory is adequate is defined. A simple numerical profile of allowed lines is also obtained, taking into account dynamic ion effects.
150 citations
TL;DR: In this paper, the optically forbidden 3s-4d transition in sodium vapor was observed using two-photon excitation with a cw dye laser and monitoring the 4d population via fluorescence cascades.
146 citations
TL;DR: In this article, the authors extended the region of validity of the previously developed low-field approximation to a wide range of energies and applied fields, and showed that the period of the oscillations is relatively unaffected by band nonparabolicities, broadening or field-distribution effects, showing that the value of the interband mass at the critical point determined from them is highly accurate.
Abstract: The complex dielectric function of a semiconductor or insulator in a uniform electric field is expressed asymptotically as the sum of a zero-field, a third-derivative, and an oscillatory (or exponential) term by appropriately deforming a contour of integration in the complex plane. The latter term describes separately the field-induced change in the dielectric function arising from Franz-Keldysh oscillations (or exponential edges). The present expansion extends the region of validity of the previously developed low-field approximation to a wide range of energies and applied fields. The stationary-phase formalism by which this term is evaluated allows the asymptotic behavior of the Franz-Keldysh oscillations to be calculated by a series of algebraic steps, a simple procedure that permits the influence of various perturbations on the Franz-Keldysh oscillations to be studied generally. We find by application of the theory that the period of the oscillations is relatively unaffected by band nonparabolicities, broadening, or field-distribution effects, showing that the value of the interband mass at the critical point determined from them is highly accurate. By contrast, the envelope of the oscillations is shown to depend strongly upon these interactions. Since Franz-Keldysh oscillations appear to be relatively unaffected by exciton effects and can be measured for several different critical points of the same crystal, measurement of their field dependence can provide a stringent means for evaluating current theories of internal-field distributions and represent and attractive alternative to exponential-absorption-edge studies for systematic investigations of these effects.
136 citations
TL;DR: In this paper, the absolute wavelengths of resolved fine-structure components of the Balmer line in hydrogen and deuterium, excited in a dc gas discharge, were measured by saturation spectroscopy with a pulsed dye laser.
Abstract: We have determined a new Rydberg value, ${R}_{\ensuremath{\infty}}=109737.3143(10)$ ${\mathrm{cm}}^{\ensuremath{-}1}$, with an order of magnitude improvement in precision, by measuring the absolute wavelengths of resolved fine-structure components of the Balmer $\ensuremath{\alpha}$ line in hydrogen and deuterium, excited in a dc gas discharge. Doppler broadening was eliminated by saturation spectroscopy with a pulsed dye laser. An iodine-stabilized He-Ne laser was the wavelength standard. Possible sources of systematic errors have been carefully investigated.
111 citations
TL;DR: In this paper, the velocity distribution function for helium in translational nonequilibrium in hypersonic free jet expansions has been investigated with an electron beam fluorescence technique with a unique computer controlled Fabry-Perot interferometer and data acquisition system.
Abstract: The velocity distribution function for helium in translational nonequilibrium in hypersonic free jet expansions has been investigated with an electron beam fluorescence technique. A unique computer controlled Fabry‐Perot interferometer and data acquisition system has been used to observe the 5015.67 A radiation from the 31 P‐21 S transition in helium. From the spectral structure, the Doppler broadening and shift of the line due to the velocity distribution function can be determined. With this technique parallel and perpendicular gas kinetic temperatures, mean flow velocity, and relative density measurements were made along the centerline of the free jet, from near equilibrium conditions through the midpoint of transition (T‖/T⊥ = 2.0). A comparison with kinetic theory predictions of the temperatures and velocity distribution functions indicate that the adoption of the ellipsoidal model, although sufficient for fitting the measured distribution function, is inadequate for determining the parallel temperat...
66 citations
TL;DR: In this article, the error in the measured wind velocity and the height definition are evaluated by taking account of the antenna characteristics, pulse and receiving gate durations, spectral broadening of the received echo, and atmospheric refraction effects.
Abstract: The operating conditions of a Doppler sodar are discussed. The error in the measured wind velocity and the height definition are evaluated by taking account of the antenna characteristics, pulse and receiving gate durations, spectral broadening of the received echo, and atmospheric refraction effects. It is shown that the measurement errors can be minimized by an adequate adjustment of the sodar operating parameters.
52 citations
TL;DR: In this article, the authors investigated the pressure broadening of the depolarized Rayleigh line at room temperature for the gases normal H 2, para H 2, HD, normal D 2, N 2, CO, CO 2 and OCS.
45 citations
TL;DR: In this paper, the X-ray emission spectrum of an ion having an inner-shell vacancy moving through a solid is discussed using Weisskopf's theory of collision broadening.
Abstract: For pt. I, see abstr. A13527 of 1974. The X-ray emission spectrum of an ion having an inner-shell vacancy moving through a solid is discussed using Weisskopf's theory of collision broadening (1933). In particular the approximations involved in a previous treatment which used the 'static' approximation are clarified. The analysis of the problem is illustrated by a direct evaluation of the emission spectrum of a model system by means of a numerical Fourier transform. The calculation demonstrates that the simpler static approximation is adequate except near the classical cut-off frequency where the dynamic variation of the molecular orbitals causes a broadening beyond this cut-off frequency. An estimate of this broadening is given.
Journal Article•
TL;DR: In this paper, a curve of growth analysis was used to relate the measured equivalent width to the line oscillator strength, and the appropriate band oscillator was calculated from this using Honl-London factors.
Abstract: Photoelectric absorption measurements have been performed on molecular hydrogen under conditions where the line profile is dominated by Doppler broadening. A curve of growth analysis was used to relate the measured equivalent width to the line oscillator strength, and the appropriate band oscillator strength was calculated from this using Honl-London factors. Oscillator strengths for eleven Lyman and six Werner bands obtained in this way show close agreement with those deduced from inelastic electron scattering data. Recent theoretical calculations are in good agreement for the Lyman bands and show only a small systematic discrepancy for the Werner bands.
TL;DR: In this paper, the mean lifetimes of the first excited states of 24 Mg and 38 Ar were measured using Doppler broadened lineshapes and scaled experimental stopping powers.
TL;DR: In this article, a generalization of the variable Eddington factor method is presented that makes possible the solution of line formation problems in extended spherical atmospheres whose constitutive properties depend on radius in an arbitrary way.
Abstract: A generalization of the variable Eddington factor method is presented that makes possible the solution of line formation problems in extended spherical atmospheres whose constitutive properties depend on radius in an arbitrary way. Extensive numerical results for Doppler broadening in models with power law opacities (n = 0, 2, 3) are presented and interpreted. Very substantial deviations are found from the solutions of analogous plane-parallel models. The single-flight escape probability is derived for a general opacity law, and is shown to exceed that for an analogous plane-parallel slab by no more than a factor of approximately two for Doppler broadening, or three-halves for Lorentz broadening. However, it is shown that each time a photon is scattered, it has a probability greater than onehalf of ending its flight at a radius larger than that at which it was emitted. This effect is peculiar to spherical geometries and may be important in aiding the escape of photons from optically thick systems. Finally the effects of dilution are considered and some properties of the infinite radius, finite optical depth models are inferred. An appendix contains the solution of the line transfer problem for a homogeneous sphere by the kernel- approximation method. (auth)
TL;DR: In this paper, a direct observation of the 3S-5S two-photon absorption in sodium vapor using a cw dye-laser was reported, and it was shown that the hyperfine structure of the 5S state is 150 ± 10 MHz.
IBM1
TL;DR: In this article, a new feature of optical free induction decay (FID) was observed in a coherently prepared sample of a cw laser beam, and was followed by FID upon sudden application of a dc Stark field that switches the molecular sample out of resonance.
Abstract: A new feature of optical free induction decay (FID) is observed in a coherently prepared sample of $^{13}\mathrm{CH}$$_{3}\mathrm{F}$ by the method of Stark switching. The preparative phase is due to the resonant steady-state excitation by a cw laser beam, and is followed by FID upon sudden application of a dc Stark field that switches the molecular sample out of resonance. The emission is not observed as a simple decay but instead appears as a train of sharp pulses regularly spaced in time as a result of a repetitive interference. This situation arises because an entire set of infrared transitions within the Stark split manifold are initially prepared, in contrast to our previous study of a nondegenerate transition. The emission, which beats with the laser, produces a heterodyne beat spectrum, consisting of a set of regularly spaced frequencies, that is the Fourier transform of the slowly decaying pulse progression observed. We thus demonstrate what is the optical analog of the well-known NMR method of high-resolution pulse Fourier spectroscopy. The detailed behavior of the pulse train agrees well with an FID theory that assumes the transitions to be uncoupled. The subtle behavior of FID near the time origin is explored also by approximate analytic expressions that reveal either a near zero amplitude or sizable amplitude depending on the degree of saturation in the preparative stage. The experimental technique discussed offers an attractive way for obtaining high-resolution optical spectra without Doppler broadening, and for generating an optical pulse train whose time scale can be compressed by simply increasing the Stark field.
TL;DR: In this paper, the Paschen-Back effect on the 3S-4D two-photon transition without Doppler broadening in sodium vapor was studied and the fine structure of the 4D state was deduced to be 1028.5 ± 3 MHz.
TL;DR: In this article, double photon absorption spectroscopy without Doppler broadening was used to measure the hyperfine separation interval in the excited 6S state and the fine structure interval of the excited 5D state of sodium vapor.
TL;DR: In this article, the effect arises from segmental diffusive motion, rather than rotations of pendant side groups, and the temperature dependence of this motion gives activation energies which are smaller than the activation energies obtained from experiments of longer time-scale such as nuclear spin-lattice relaxation measurements and viscometry.
Abstract: Neutron scattering experiments on polymethylphenylsiloxane, polypropylene oxide, polyiso butylene and polyethylene oxide show broadening in the quasi-elastic region similar to that previously reported from polydimethylsiloxane. Measurements on partially deuterated samples confirm that the effect arises from segmental diffusive motion, rather than rotations of pendant side groups. The temperature dependence of this motion gives activation energies which are smaller than the activation energies for self-diffusion obtained from experiments of longer time-scale such as nuclear spin-lattice relaxation measurements and viscometry.
TL;DR: In this paper, the Doppler shift can provide velocity resolution in excited-state molecular-collision experiments which is comparable to that obtainable in molecular-beam machines, and the state of the quasimolecule formed in the collision can be selected.
Abstract: We show that the Doppler shift can provide velocity resolution in excited-state molecular-collision experiments which is comparable to that obtainable in molecular-beam machines. In addition, the state of the quasimolecule formed in the collision can be selected.
TL;DR: In this article, the spectral line shape of hyper-Raman light scattering in liquids is calculated by the method of irreducible spherical tensors and the theory of rotational Brownian motion.
Abstract: The spectral line shape of hyper-Raman light scattering in liquids is calculated by the method of irreducible spherical tensors and the theory of rotational Brownian motion. The line broadening due to rotational molecular motion in the liquid is expressed by way of relaxation times τ and is found to depend on nonlinear molecular parameters ∣B∣2, which are quadratic functions of the derivatives with respect to appropriate normal coordinates of the hyperpolarizability tensor elements b. Tables of ∣B∣2 are adduced for all vibration symmetries of spherical-top and symmetric-top molecules. The tensor elements of scattered light intensity are calculated for linearly and circularly polarized incident light. Investigation of hyper-Raman spectral line broadening is seen as a source of new data on the dynamics of molecules in the liquid state and on their nonlinear optical properties.
TL;DR: In this paper, the authors studied the effect of mean transverse wind on the frequency spectrum of an acoustic plane-wave pulse backscattered into a finite-angle receiver by the action of a transverse mean wind.
Abstract: The analysis studies the broadening of the frequency spectrum of an acoustic plane‐wave pulse backscattered into a finite‐angle receiver by the action of a transverse mean wind which moves turbulent velocity and temperature fluctuations through the beam. The results include the frequency spectrum I(k) of the acoustic pressure as a function of wavenumber and the spectral equivalent width b, as a function of mean transverse wind speed and receiver aperture. For broad beams, both temperature and velocity fluctuations contribute to the apparent 180°‐backscatter intensity, and the contributing eddy scales vary from λ/2 to λ/√2. Again for broad beams and for typical experimental parameters for atmospheric echosondes, the broadening effects of mean transverse wind in the scattering volume outweigh the broadening effects of turbulence trransported by a mean transverse wind during propagation to the scattering volume. However, as the receiver beam angle decreases, the spectral broadening drops to zero, regardless of mean wind. Figures are included to show the effects of wind broadening for the case of intermediate receiver beam angles.The analysis studies the broadening of the frequency spectrum of an acoustic plane‐wave pulse backscattered into a finite‐angle receiver by the action of a transverse mean wind which moves turbulent velocity and temperature fluctuations through the beam. The results include the frequency spectrum I(k) of the acoustic pressure as a function of wavenumber and the spectral equivalent width b, as a function of mean transverse wind speed and receiver aperture. For broad beams, both temperature and velocity fluctuations contribute to the apparent 180°‐backscatter intensity, and the contributing eddy scales vary from λ/2 to λ/√2. Again for broad beams and for typical experimental parameters for atmospheric echosondes, the broadening effects of mean transverse wind in the scattering volume outweigh the broadening effects of turbulence trransported by a mean transverse wind during propagation to the scattering volume. However, as the receiver beam angle decreases, the spectral broadening drops to zero, regardless ...
TL;DR: The phonon frequency spectra developed for U and O in UO 2 by Thorson and Jarvis (1969) were used to deduce the effective temperatures for these two nuclides, and some comments were made on the effect of crystalline binding on the temperature broadening of resonances in uranium as mentioned in this paper.
TL;DR: In this paper, the structure of the quasielastic incoherent neutron scattering from polydimethyl siloxane has been determined at low momentum transfer under conditions of high resolution.
TL;DR: In this paper, the effects of photon frequency redistribution in semi-infinite and slab, differentially moving atmospheres are examined for the case of pure Doppler broadening as described by the angle-averaged redistribution function.
Abstract: The effects of photon frequency redistribution in semi-infinite and slab, differentially-moving atmospheres are examined for the case of pure Doppler broadening as described by the angle-averaged redistribution function. Results are obtained for the frequency dependent non-LTE line source functions and their corresponding emergent line intensities. These emergent line intensities are compared with those obtained assuming complete redistribution and are found to be exceedingly different in the line core.
TL;DR: In this article, the authors used high-frequency deflection technique to measure radiative lifetimes for the 4p and 5p upper states in Na I, along with relative populations of a number of ns and nd states.
Abstract: Use of the high-frequency deflection technique to measure radiative lifetimes for the 4p and 5p upper states in Na I, along with relative populations of a number of ns and nd states. These data have been used to obtain f-values for the corresponding resonance transitions in Na I, which proved to be in reasonable agreement with previous oscillator strengths. From the theoretical curve of growth for pure Doppler broadening, revised line ratios for D1/3303 are given and are compared with observations of Na I in zeta Oph.
TL;DR: In this paper, the Doppler effect reduces the radiative interaction between identical atoms so that only those for which k
Abstract: The Doppler effect reduces the radiative interaction between identical atoms so that only those for which k. Delta v
TL;DR: In this paper, a new approach was proposed to obtain narrow and tunable spectral lines of positronium annihilation radiation (H ω λ = 0511 MeV ) based on the conversion of ortho-positronium atoms with a certain velocity of motion to the para-positionion under the effect of laser radiation and magnetic field.