Showing papers on "Doppler broadening published in 1981"
TL;DR: In this article, a measurement of the splitting of the discrete lines in the 5-min oscillations of the solar surface produced experimental evidence for the rapid internal rotation of the Sun, and the number of components into which the lines are split also allows unambiguous identification of 11 examples of each of the l = 0, l = 1 and l = 2 modes in the frequency range 2.40-3.85 mHz.
Abstract: The observation of line-of-sight velocities of the solar surface by means of Doppler shift measurements of the Fraunhofer absorption lines, using optical resonance scattering, has proved a useful technique in solar physics enabling the discovery of long period solar oscillation1, the discrete, regular structure in the 5-min oscillation2 and, as we report here the splitting of this structure by rotational effects. A measurement of the splitting of the discrete lines in the 5-min oscillations of the solar surface produced experimental evidence for the rapid internal rotation of the Sun. These data demonstrate that the Sun does not rotate uniformly but that the ‘core’ of the Sun rotates 2–9 times as rapidly as the observed surface rotation. The number of components into which the lines are split also allows unambiguous identification of 11 examples of each of the l = 0, l = 1 and l = 2 modes in the frequency range 2.40–3.85 mHz.
116 citations
58 citations
TL;DR: In the turbulent heating experiment of the high-field tokamak TRIAM-1, the bulk ion heating shown by the neutral energy analyzer measurement is confirmed by the Doppler broadening measurement of visible lines.
Abstract: In the turbulent heating experiment of the high-field tokamak TRIAM-1, the bulk ion heating shown by the neutral energy analyzer measurement is confirmed by the Doppler broadening measurement of visible lines. The increasing rate and decay time of the Doppler ion temperature are almost the same as those derived from the neutral energy analyzer measurement. From both methods of ion temperature measurements, it is shown that the ion temperature has a parabolic profile within 50 µs after the application of the heating pulse.
56 citations
TL;DR: In this paper, the Doppler broadening technique was used to determine the monovacancy formation enthalpy (H1vF) of Ni using the DoP broadening method and a comparison was made with previous self-diffusion results.
Abstract: The monovacancy formation enthalpy, H1vF, was determined for Ni using the Doppler broadening technique. The 58Co positron source was ion implanted in Ni of 99.995 wt.% purity. A 103Ru gamma -ray line (497 keV) was recorded simultaneously with the positron annihilation 511 keV line, and was used in stabilising the data. Measurements were performed on three similar Ni samples, which were annealed in an ultra-high vacuum chamber (10-8-10-9 Torr) at approximately 30 degrees C below their melting point for at least two hours prior to the in situ measurements. For one of the samples, a comparison was made of H1vF values deduced prior to and after in situ melting. A value of H1vF=1.8+or-0.1 eV was determined from the present data. In addition, a value for the monovacancy migration enthalpy, H1vM=1.1+or-0.1 eV, has been deduced from a comparison of the present H1vF measurement with previous self-diffusion results.
54 citations
TL;DR: Resolution sufficient to resolve second-order Doppler broadening has been obtained for the Ca (1)S(0)-(3)P(1) transition (657 nm) by using an atomic beam and optical Ramsey fringe techniques.
Abstract: Resolution sufficient to resolve second-order Doppler broadening (3.9 kHz) has been obtained for the Ca 1S0–3P1 transition (657 nm) by using an atomic beam and optical Ramsey fringe techniques. Laser-beam separations up to 21 cm yield Ca linewidths (HWHM) as narrow as 1 kHz. As resolution is increased to approach, then exceed, the second-order linewidth, large asymmetries, shifts, and shape changes occur in the Ramsey fringe profile.
52 citations
TL;DR: In this paper, a theory of the incoherent scattering cross section from high frequency intramolecular vibrational modes (ωλ) in a molecular crystal is given, where the scattering from a ωλ mode is proportional to a Debye-Waller factor arising only from the internal molecular modes, multiplied by Ss(K, ω−ωλ), where Ss is the self-correlation function of the molecular lattice.
Abstract: A theory is given of the incoherent scattering cross section from high frequency intramolecular vibrational modes (ωλ) in a molecular crystal. It is assumed that ωλ≫ωD, where ωD is the maxium frequency of the low frequency lattice phonon continuum. It is shown that the scattering from a ωλ mode is proportional to a Debye–Waller factor arising only only from the internal molecular modes, multiplied by Ss(K,ω−ωλ), where Ss(K, ω) is the self‐correlation function of the molecular lattice. In the case when the Debye–Waller factor due to the lattice phonons is negligibly small, we show that Ss(K, ω−ωλ) is a Gaussian in ω−ωλ with Doppler broadening due to translational and rotational motion. Our theory is a development of the short‐time approximation and explains the unexpectedly strong intensity of the C–H stretching and bending modes recently observed by Jobic, Ghosh, and Renouprez in hexamethylenetetramine (HMT). The present paper gives the theoretical basis for the quantitative interpretation of the high energy intramolecular vibrational spectrum measured by inelastic neutron scattering.
45 citations
TL;DR: In this paper, a phase-stabilised Michelson interferometer is used as sensitive spectrometer, generating a continuous electrical signal that follows proportionally and with a mu s time constant the wavelength changes of the Doppler shifted scattered light.
Abstract: A phase-stabilised Michelson interferometer is used as sensitive spectrometer, generating a continuous electrical signal that follows proportionally and with a mu s time constant the wavelength changes of the Doppler shifted scattered light. Thus a real-time velocity signal is available. The different aspects arising from various applications are discussed, for example high sensitivity for small velocities, high time resolution, cases of low level and discontinuous scattered light. Typical examples are given showing the performance of the system in recording both surface movements and flow velocities.
36 citations
TL;DR: In this paper, the first observation of saturation broadening in a high-resolution coherent Raman spectrum of the v 2 Q-branch of acetylene was reported, which is significantly greater than the calculated ac Stark broadening of less than 100 MHz.
33 citations
TL;DR: In this paper, the Doppler profiles of line shapes observed by laser induced fluorescence are used to recover level-specific differential cross sections in crossed molecular beam experiments from the Dopper profile.
Abstract: We discuss two methods, one of them new, for recovering level‐specific differential cross sections in crossed molecular beams experiments from the Doppler profiles of line shapes observed by laser induced fluorescence. The angular resolutions of the two methods are compared and shown to be complementary. An experiment using both methods can have moderately good angular resolution at all scattering angles. In the first method, which has previously been demonstrated experimentally, the Dopper profile is taken with the laser beam parallel to the relative velocity of the collision system. Good angular resolution is obtained between π/4 and 3π/4. In the second method, which is proposed here, the Doppler profile is taken with the laser beam perpendicular to this relative velocity, and the best angular resolution is obtained in the regions 0 to π/4 and 3π/4 to π. This method requires an integral transform to recover the cross section from the Doppler profile. A practical implementation of this transform is presented along with a numerical example showing its relative insensitivity to noise in the profile.
28 citations
01 Aug 1981
TL;DR: In this article, a crossed beam CARS technique of high spatial resolution including non-resonant background cancellation is employed to determine local temperatures and hydrogen concentrations in an ethylene-air Bunsen flame.
Abstract: Local temperatures and hydrogen concentrations in an ethylene-air Bunsen flame have been determined from CARS measurements of the Q(0) to Q(4) [υ = 1 υ = 0] Raman transitions in hydrogen. A crossed beam, BOXCARS, technique of high spatial resolution including non-resonant background cancellation is employed. The linewidth correction is taken into account for the limit of Doppler broadening. The results agree well with thermodynamic equilibrium calculations.
28 citations
TL;DR: In this article, the rotational analysis of the congested spectra of the BaI radical was carried out by optical-optical double resonance method by exciting fluorescence, and the results showed that the AIP method was more accurate than the conventional single resonance method.
Abstract: The rotational analysis of the congested spectra of the BaI radical is carried out by optical–optical double resonance method by exciting fluorescence. (AIP)
TL;DR: In this paper, age-hardenable Al-Zn-Mg alloys have been studied by positron lifetime, Doppler broadening and angular correlation measurements.
Abstract: Age-hardenable Al-Zn-Mg alloys have been studied by positron lifetime, Doppler broadening and angular correlation measurements. Zinc-rich Guinier-Preston zones in the Al-Zn alloy are observed to trap positrons. In the quenched alloys containing magnesium, positrons are localized at stable vacancy-type defects, which are evidently bound to Mg atoms. Some indications of positron trapping by incoherent precipitate-matrix interfaces are also shown.
TL;DR: In this paper, a detailed analysis of Stark broadening parameters as functions of the impact electron angular momentum quantum number and of the temperature was carried out, and the influence of the polarisation potential and the completeness of the set of energy levels on the Stark broadeners was investigated.
Abstract: The authors present quantum mechanical calculations of Stark broadening parameters for the Li I 2s2S-2p2P line. Semiclassical calculations have also been performed and both have been compared with other available results. A detailed analysis of Stark broadening parameters as functions of the impact electron angular momentum quantum number and of the temperature is carried out. The influence of the polarisation potential and of the completeness of the set of energy levels on the Stark broadening parameters is investigated. The low temperature behaviour of the half width is discussed too.
TL;DR: In this paper, different influences of various types of broadening (pressure, Doppler, Stark and resonance) after the convolution of each profile, on the spectral interferences resulting from overlap of line wings are also discussed.
TL;DR: In this paper, the authors measured the linewidth of the ν 2 + ν 4 R + (29) A 1 4 + E 9 + F 1 14 absorption at 1073.279 cm −1 in the pressure range of 0.5 to 50 Torr CF 4.
TL;DR: In this article, various polarisation selection rules guiding phase conjugate emission via degenerate four-wave mixing are discussed, and it is shown that depolarising collisions may induce phase conjUGation in cases when this non-linear process is otherwise forbidden.
Abstract: Various polarisation selection rules guiding phase conjugate emission via degenerate four-wave mixing are discussed. It is shown that, in resonant gas media, depolarising collisions may induce phase conjugation in cases when this non-linear process is otherwise forbidden. However, Doppler broadening often limits the efficiency of non-collinear collision-induced four-wave mixing, and introduces a very rapid decrease of the reflectivity with increasing angular separations between pump and probe beams.
TL;DR: In this paper, the impact broadening of the potassium 4p2P1/2-7s2S 1/2 (5782 AA) lines by helium and argon foreign gases has been studied interferometrically in the emission spectrum of a low-current electrical discharge.
Abstract: The impact broadening of the potassium 4p2P1/2-7s2S1/2 (5782 AA) and 4p2P3/2-7s2S1/2 (5802 AA) lines by helium and argon foreign gases has been studied interferometrically in the emission spectrum of a low-current electrical discharge. Unlike the resonance lines and other transitions from low-lying states, the broadening and shift rates here are so large that very significant effects are observable with conventional spectroscopy at gas pressures as low as 10 Torr. The observed effects are interpreted with impact broadening calculations based on the pseudopotential interactions computed by Pascale and Vandeplanque (1974), and on the Fermi-type potential proposed by Roueff (1970). The pseudopotentials underestimate considerably the observed broadening and shift, while the Fermi potential gives an improved, although not entirely satisfactory, agreement. Potentials deduced for the 7s2S1/2 state by fitting power-law interactions to the observed broadening and shift rates have a long-range attraction for argon and a long-range repulsion for helium. These fitted interaction potentials are about an order of magnitude stronger than the pseudopotential calculations for the internuclear separations of approximately 20 AA that contribute most significantly to the broadening and shift.
TL;DR: In this paper, the authors show that quantum-well size changes δLz = δLB can be observed, via luminescence or laser spectral shifts, on all-binary, active region (AlAs•GaAs) QWHs or superlattices (SLs) with coupling barrier sizes LB <50 A.
Abstract: In AlxGa1−x As‐GaAs quantum‐well heterostructures (QWH’s) or superlattices (SL’s) with coupling barrier sizes LB <50 A, alloy clustering, owing simply to fluctuations in the random Al‐Ga arrangement, causes effective changes in quantum‐well size and, as a consequence, a decrease in energy and broadening of the confined‐particle states. Data are presented showing that actual quantum‐well size changes δLz = δLB can be observed, via luminescence or laser spectral shifts, on all‐binary, active‐region (AlAs‐GaAs) QWH’s or SL’s. The small spectral broadening and downward shift indicate a size change δLz = δLB as small as a monolayer for high‐energy, all‐binary QWH and SL structures grown by metal‐organic chemical vapor deposition. Narrow‐spectrum cw 300‐K laser operation has been realized at λ∼7500 A, and should be possible to λ≲6785 A.
TL;DR: In this article, a simple method for an accurate subtraction of the underlying nonlinear background from positron annihilation spectra is described, which employs a step function, complemented by a modified version of the error function, without assuming any functional form of the 511 keV peak.
TL;DR: In this paper, the Doppler broadening of the 511-keV photons resulting from positron annihilation in a single cadmium crystal over the temperature range 4-590 K was measured.
Abstract: Measurements have been made on the Doppler broadening of the 511-keV photons resulting from positron annihilation in a single cadmium crystal over the temperature range 4-590 K. They show that the temperature dependence in the prevacancy region (150-350 K) is markedly different in the cases of emission in the [0001] and $[10\overline{1}0]$ directions.
TL;DR: For small input intensities, asymptotic approximations for the dependence of sum frequency mixing on the pump laser linewidth, Doppler broadening, pressure broadening and pump laser detuning were derived in this paper.
TL;DR: In this article, the pressure broadening of the different K components of the J=3-4 rotational line of CH3CN was measured using a very small cell with an acoustic detector and a comparison with theoretically estimated linewidths was discussed.
Abstract: The pressure broadening of the different K components of the J=3–4 rotational line of CH3CN have been measured. A novel experimental apparatus employing a very small cell with an acoustic detector is described and a comparison with theoretically estimated linewidths is discussed.
TL;DR: In this paper, an investigation was made of selective specular reflection from 133Cs vapor in the range of atomic concentrations between 4×1013 and 2×1015 cm−3 where collisional broadening of the D2 line is less than the Doppler broadening.
Abstract: An investigation was made of selective specular reflection from 133Cs vapor in the range of atomic concentrations between 4×1013 and 2×1015 cm−3 where collisional broadening of the D2 line is less than the Doppler broadening. The radiation source was an injection laser. Intra-Doppler resonances corresponding to the hyperfine structure of the excited state were recorded in the selective reflection profile. Shifts of the reflection resonances relative to the luminescence resonances of the atomic beam did not exceed 50 MHz. The possiblity of using selective reflection for linear spectroscopy of atomic lines without Doppler broadening is discussed.
TL;DR: In this article, an experimental system was used for obtaining Ramsey fringes with an atomic beam for the Ca 657 nm line, and for the system which was being set up to obtain fringe with a large absorption cell for various molecules in the 10 µm region.
Abstract: A description is given of the experimental system which was used for obtaining Ramsey fringes with an atomic beam for the Ca 657 nm line, and for the system which is being set up to obtain fringes with a large absorption cell for various molecules in the 10 µm region. Details of the cat's eye and segmented retroreflector optical systems are discussed. Results obtained with Ca include fringe widths as small as 1 kHz HWHM, resolution of the recoil splitting, and resolution of second-order Doppler broadening and shift. The experiment at 10 µm is in progress and has already yielded a 1.25 kHz linewidth (HWHM) for the single zone signal with the SF6 molecule.
01 Jan 1981
TL;DR: The discovery of emission and absorption of γ rays free of thermal Doppler broadening and the effects of recoil by R.L. MOSSBAUER [3] brought to experimental physics a tool that has been used to detect fractional changes of electromagnetic energy smaller than can be detected by any other technique as mentioned in this paper.
Abstract: The discovery of emission and absorption of γ rays free of thermal Doppler broadening and the effects of recoil by R.L. MOSSBAUER [3.1] brought to experimental physics a tool that has been used to detect fractional changes of electromagnetic energy smaller than can be detected by any other technique. One of the earliest and most striking applications was the confirmation of the effect of gravity on photon energy as predicted by A. Einstein. The general background and some details of the most thorough of such studies will be described herein.
TL;DR: In this paper, two lineshape parameters S and W were defined for the central and the tail portions of the spectrum, respectively, and it was shown that the fractional change of the W parameter is about one order of magnitude larger than that of the S parameter.
Abstract: Doppler broadened spectra of positron annihilation in an aluminium crystal were measured for 59 different temperatures from 298 to 897K. The instrumental response function was unfolded from observed annihilation spectra and intrinsic distributions were obtained. Two lineshape parameters S and W were defined for the central and the tail portions of the spectrum, respectively. It was shown that the fractional change of the W parameter is about one order of magnitude larger than that of the S parameter. The temperature dependence of S and W parameters in the prevacancy region does not correspond to that of the lattice volume. In addition, the S parameter shows strong temperature dependence in the high temperature region, in contrast to the W parameter which saturates in this region. Using the trapping model the vacancy formation enthalpy was obtained from the result. The value strongly depends on the fitting function for the lineshape parameters.
TL;DR: Positron lifetime and Doppler broadening measurements have been carried out on GeS1.375 and GeS 1.5 glasses as mentioned in this paper, and the positron annihilation parameters were found non-sensitive to fast neutron irradiation doses as high as 1019 n/cm2.
Abstract: Positron lifetime and Doppler broadening measurements have been carried out on GeS1.375 and GeS1.5 glasses. A pronounced decrease of the mean lifetime was observed at crystallization of GeS1.375 glass into the GeS structure. Also the Doppler-broadened curves are strongly sensitive to this solid-solid phase transition. Unlike the situation for many metals, the positron annihilation parameters were found non-sensitive to fast neutron irradiation doses as high as 1019 n/cm2. No difference between positron annihilation parameters measured on GeS1.375 and GeS1.5 glasses was found. The state of the positron in the GeS glasses is discussed on the basis of these results. The idea is put forward, that the GeS-GeS2 system provides possibilities of sample parameter variations that might prove useful in the understanding of the positron state in non-metallic solids.
TL;DR: In this article, a toroidal mirror was used as focusing element to achieve a high spatial resolution on the XUV emission of laser-produced plasmas in the X-UV region, which can be interpreted as a motional Doppler shift.
Abstract: The emission of laser-produced plasmas in the XUV region has been observed with a novel technique that uses a toroidal mirror as focusing element, achieving a high spatial resolution on the plasma. The profiles of the resonance lines Be IV Lyman α and Be III 1s2-1s 2p appear symmetrically split in two components far from the target (> mm). This effect, observed also for other resonance lines, can easily be interpreted as a motional Doppler shift. This indicates a minimum of ion density in the centre of the plasma expanding in a near conelike shape around the normal to the target.