Shock-tube measurements of Van der Waals broadened silicon lines.
Widths measurements of van der Waals broadened Si I spectral lines by shock tube and scanning Fabry-Perot interferometer, using argon as perturbing gas
Day, R. A.↗
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Results for “LINE WIDTHS”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Nitrogen, oxygen and air broadened widths and relative intensities of N2O lines near 2450/cm
Spectra of the v sub 1 + 2v sub 2 and the weak underlying v sub 1 + 3v sub 2 - v sub 2 band of N2O near 2450/cm were analyzed by the nonlinear, least squares, whole band technique. The oxygen, nitrogen, and air broadened line widths and the relative line intensities were determined. The air broadened widths, for/m/3, are in agreement with those in the 1980 AFGL line listing and the relative band intensities also agree, within about 20% with the values in this listing.
Hawkins, R. L.↗
Nitrogen-, oxygen-, and air-broadened widths and relative intensities of N2O lines near 2450 per cm
Spectra of the v sub 1 + 2v sub 2 and the weak underlying v sub 1 + 3v sub 2 - v sub 2 band of N2O near 2450/cm were analyzed by the nonlinear, least squares, whole band technique. The oxygen, nitrogen, and air broadened line widths and the relative line intensities were determined. The air broadened widths, for /m/3, are in agreement with those in the 1980 AFGL line listing and the relative band intensities also agree, within about 20 percent with the values in this listing. Previously announced in STAR as N82-30201
Hawkins, R. L.↗
Unresolved velocity structure in diffuse interstellar clouds
Recent high-resolution observations of interstellar absorption lines of CH and CN toward Zeta Oph obtained by Crane et al. (1986), and Palazzi et al. (1988), exhibit line widths that suggest thermal line broadening at high temperature, T about 1200 K. Observations of CO line emission at 2.6 mm toward Zeta Oph (Langer et al.,1987) indicate that the molecular gas resides in four distinct velocity components that span less than 3 km/s in Doppler velocity. Simulated CH and CN absorption line profiles are compared for high-temperature (T = 1200 K) thermal broadening and for a combination of low-temperature (T = 50 K) thermal plus turbulent broadening. It is shown that the two broadening models reproduce existing observations comparably well and are virtually indistinguishable at a lambda/Delta-lambda ratio of about 100,000. The observed differences in the CH and CN line widths may reflect slightly different distributions of those molecules along the line of sight. The simulations use very recent, improved laboratory spectroscopic data on CH (Bernath). Some related consequences of such unresolved velocity structure on the ultraviolet absorption lines of CO are examined. Indirect diagnostics of temperature in the Zeta Oph cloud favor low-temperature thermal plus turbulent broadening, and the implied rate of dissipation of turbulence is in harmony with estimates of the global input of mechanical energy into to interstellar medium.
Black, John H.↗
Solar Flare Heating with Turbulent Suppression of Thermal Conduction
During solar flares plasma is typically heated to very high temperatures, and the resulting redistribution of energy via thermal conduction is a primary mechanism transporting energy throughout the flaring solar atmosphere. The thermal flux is usually modeled using Spitzer’s theory, which is based on local Coulomb collisions between the electrons carrying the thermal flux and those in the background. However, often during flares, temperature gradients become sufficiently steep that the collisional mean free path exceeds the temperature gradient scale size, so that thermal conduction becomes inherently non-local. Further, turbulent angular scattering, which is detectable in nonthermal widths of atomic emission lines, can also act to increase the collision frequency and so suppress the heat flux. Recent work by Emslie & Bian (2018) extended Spitzer’s theory of thermal conduction to account for both non-locality and turbulent suppression. We have implemented their theoretical expression for the heat flux (which is a convolution of the Spitzer flux with a kernel function) into the RADYN flare-modeling code and performed a parameter study to understand how the resulting changes in thermal conduction affect flare dynamics and hence the radiation produced. We find that models with reduced heat fluxes predict slower bulk flows, less intense line emission, and longer cooling times. By comparing features of atomic emission lines predicted by the models with Doppler velocities and nonthermal line widths deduced from a particular flare observation, we find that models with suppression factors between 0.3 to 0.5 relative to the Spitzer value best reproduce observed Doppmission lines forming over a wide range of temperatures. Interestingly, the model that best matches observed nonthermal line widths has a kappa-type velocity distribution function.
Joel C. Allred↗
Solar Flare Heating with Turbulent Suppression of Thermal Conduction
During solar flares plasma is typically heated to very high temperatures, and the resulting redistribution of energy via thermal conduction is a primary mechanism transporting energy throughout the flaring solar atmosphere. The thermal flux is usually modeled using Spitzer’s theory, which is based on local Coulomb collisions between the electrons carrying the thermal flux and those in the background. However, often during flares, temperature gradients become sufficiently steep that the collisional mean free path exceeds the temperature gradient scale size, so that thermal conduction becomes inherently non-local. Further, turbulent angular scattering, which is detectable in nonthermal widths of atomic emission lines, can also act to increase the collision frequency and so suppress the heat flux. Recent work by Emslie & Bian (2018) extended Spitzer’s theory of thermal conduction to account for both non-locality and turbulent suppression. We have implemented their theoretical expression for the heat flux (which is a convolution of the Spitzer flux with a kernel function) into the RADYN flare-modeling code and performed a parameter study to understand how the resulting changes in thermal conduction affect flare dynamics and hence the radiation produced. We find that models with reduced heat fluxes predict slower bulk flows, less intense line emission, and longer cooling times. By comparing features of atomic emission lines predicted by the models with Doppler velocities and nonthermal line widths deduced from a particular flare observation, we find that models with suppression factors between 0.3 to 0.5 relative to the Spitzer value best reproduce observed Doppler velocities across emission lines forming over a wide range of temperatures. Interestingly, the model that best matches observed nonthermal line widths has a kappa-type velocity distribution function
Solar flares↗
A search for a turbulent-free region in the solar transition zone
A search for a turbulence-free transition-zone region was conducted. The data used were spectra recorded by a slit spectrograph on Skylab. It was found that the nonthermal turbulent motions are smallest in certain active regions and quiescent prominences. The spectra of one such region, a quiescent prominence, are discussed. The nonthermal turbulence in the region is between about 2 and 7 km/s. Therefore, the widths of lines emitted by transition-zone ions are determined primarily by the ion temperature. To within the experimental error, temperatures derived from the line widths are equal to the temperatures of maximum emitting efficiency obtained using the ionization equilibrium calculations of Jordan (1969).
Feldman, U.↗
Radiative widths and splitting of cyclotron lines in superstrong magnetic fields
The radiative line widths of the Landau levels in a superstrong magnetic field are calculated and simple analytic expressions and fits are given for these which are valid over a wide range of the principal quantum number and the magnetic field strength. If QED corrections are not taken into account, all levels but the first are doubly degenerate, corresponding to the two possible spin projections. However, the interaction with the QED vacuum removes this degeneracy, leading to an energy splitting of each level which exceeds the radiative linewidth for low Landau levels if the magnetic field is not too large (B is less than approximately 10 exp 13 G). Estimations are presented of the splitting in various limits as a function of field strength and Landau number. The possibility of observing this splitting in accreting X-ray pulsars and in gamma-ray bursters is discussed.
Pavlov, G. G.↗
A kinematic and proper-motion survey of the Cygnus Loop
H-alpha radial velocities, line widths, and line intensities based on 71 Fabry-Perot interferometer scans of 61 fields in the Cygnus Loop supernova remnant SNR are reported. Also, measurements of proper motions at 39 locations within the Cygnus Loop are summarized. These results show that the remnant is expanding asymmetrically into the ambient interstellar medium, with rest-frame velocities as high as 380 km/s in the near half and 150 km/s in the far half. This can plausibly be interpreted as the result of the progenitor's evolution near a density discontinuity, the consequent formation of a cavity and partial shell, and the SN's interaction with that shell. The remnant's optically observed filamentary structure results from line-of-sight effects as shock waves advance into the irregular inner surface of the shell. In this context, the derived expansion velocities and proper motions give a formal distance to the Cygnus Loop of roughly 600 pc, with 1-sigma limits of 300 and 1200 pc.
Shull, Peter, Jr.↗
Infrared spectroscopy of cometary parent molecules
The wealth of information on cometary physics provided by high-resolution spectroscopy of the IR water transitions is discussed. Specifically, the absolute line intensities and spatial brightness profiles are used to determine water production rates and lifetimes; the relative line intensities and spatial brightness profiles are used to determine water production rates and lifetimes; the relative line intensities probe the kinetic temperature profile in the coma; the line widths and line positions shed light on the coma outflow dynamics; and the temporal variability in the lines provides information on the structure of the nucleus. These observations also make it possible to determine the water ortho-to-para ratio, which may elucidate the origin and/or evolution of cometary nuclei. Recent advances in IR instrumentation promise to extend sensitivities for parent molecule searches to relative abundances well below 1 percent, especially if cooled, earth-orbiting facilities are available.
Weaver, H. A.↗
Erratum: The 2.27 day period of WR-134 (HD 191765)
The original temporal analysis of a 12 night spectral timeseries of Wolf-Rayet (WR)-134 has been found to be flawed and a re-analysis shows that the line profile variations are indeed periodic. When combined with a 4 night timeseries taken 45 days earlier, a period near 2.27 d is found in periodograms of the He II lambda 5412 line centroid, rms line width, and line skew variations. When the emission line residuals are ordered as a function of phase, a sinuous feature appears to 'snake' about the line center with an amplitude of +/-500 km/s. This is approximately equal to 20 larger than the line centroid amplitude; the calculation of which is heavily weighted by static portions of the line profile. In addition to the 'snake,' emission residuals appear that move away from line center on unbound trajectories and are thought to result from the interaction of a periodic driver with the unstable flow of the radiation driven wind.
Mccandliss, Stephan R.↗
Experimental and theoretical studies on collision-broadened lines in the nu-4 fundamental of methane.
High-resolution experimental and theoretical studies performed earlier by us on the collision-broadened rotational lines in the nu-3 and 2nu-3 bands of methane have been repeated on the lines in the nu-4 fundamental of the molecule. Line-width measurements and computations, as well as line-shape measurements, indicate that the significant differences which exist between the rotational term values of the nu-3 and nu-4 vibrational levels have no observable effect on the collision-broadening mechanism. Using the predictions of line-widths, based on the Anderson-Tsao-Curnutte theory in the extended version of Tejwani for octopolar molecules, the theoretical dependence of line-widths on temperature has been calculated for CH4-CH4, CH4-H2 and CH4-He collisions.
Varanasi, P.↗
A C(18)O survey of dense cores in the Taurus molecular cloud: Signatures of evolution and protostellar collapse
We have mapped 11 dense cores in the Taurus molecular cloud in the C(18)O J = 2 goes to 1 line at a linear resolution of 0.02 pc. The core masses derived from C(18)O range from 0.06 to 5 solar mass. Five of them have embedded infrared sources, and six do not. Dense cores without infrared sources show multiple emission peaks. In contrast, dense cores with infrared sources have a single peak and smaller sizes. The cores with infrared sources have line widths that are 2-3 times the value expected from correlations found in previous surveys. This enhancement may be accounted for by models of gravitational collapse. The data are consistent with the idea that dense cores evolve first toward smaller sizes and smaller line width along the line width-size relation, and then toward larger line width and constant or smaller sizes as an infrared source becomes observable. A good collapse candidate, L1527, is identified based on the shapes of C(18)O and H2CO lines.
Zhou, Shudong↗
A study of the strengths and widths of lines in the 9.4 and 10.4 mu CO sub 2 bands.
Strengths and widths of lines in 9.4 and 10.4 mu carbon dioxide bands by measuring transmittance vs pressure, using curve of growth method
Mccubbin, T. K., Jr.↗
Characterization of lunar ferromagnetic phases by the effective linewidth method
The effective line-width technique, first developed to study the physics of microwave relaxation in ferrites, has been successfully applied to lunar matter. Effective line-width measurements have been made on two selected samples containing disperse spherical metallic iron particles below 40 microns in diam. The data were obtained for fields from 7 to 12 kOe and a temperature range 125 - 300 K. The effective line width was field-independent and temperature-independent at 650 - 750 Oe. The high-field tails of the ferromagnetic resonance absorption were highly Lorentzian. From the relatively large and temperature-independent high-field effective line widths, it appears that (1) the metallic iron phases in lunar soil are rather impure; (2) the impurities are passive, in that there is no evidence for a temperature peak process; and (3) these samples contain no appreciable magnetite.
Patton, C. E.↗
Study of Structure and Small-Scale Fragmentation in TMC-1
Large-scale C(sup 18)O maps show that the Taurus molecular cloud 1 (TMC-1) has numerous cores located along a ridge which extends about 12 minutes by at least 35 minutes. The cores traced by C(sup 18)O are about a few arcminutes (0.1-0.2 pc) in extent, typically contain about 0.5-3 solar mass, and are probably gravitationally bound. We present a detailed study of the small-scale fragmentary structure of one of these cores, called core D, within TMC-1 using very high spectral and spatial resolution maps of CCS and CS. The CCS lines are excellent tracers for investigating the density, temperature, and velocity structure in dense cores. The high spectral resolution, 0.008 km /s, data consist mainly of single-dish, Nyquist-sampled maps of CCS at 22 GHz with 45 sec spatial resolution taken with NASA's 70 m DSN antenna at Goldstone. The high spatial resolution spectral line maps were made with the Very Large Array (9 sec resolution) at 22 GHz and with the OVRO millimeter array in CCS and CS at 93 GHz and 98 GHz, respectively, with 6 sec resolution. These maps are supplemented with single-dish observations of CCS and CC(sup 34)S spectra at 33 GHz using a NASA 34 m DSN antenna, CCS 93 GHz, C(sup 34)S (2-1), and C(sup 18)O (1-0) single-dish observations made with the AT&T Bell Laboratories 7 m antenna. Our high spectral and spatial CCS and CS maps show that core D is highly fragmented. The single-dish CCS observations map out several clumps which range in size from approx. 45 sec to 90 sec (0.03-0.06 pc). These clumps have very narrow intrinsic line widths, 0.11-0.25 km/s, slightly larger than the thermal line width for CCS at 10 K, and masses about 0.03-0.2 solar mass. Interferometer observations of some of these clumps show that they have considerable additional internal structure, consisting of several condensations ranging in size from approx. 10 sec- 30 sec (0.007-0.021 pc), also with narrow line widths. The mass of these smallest fragments is of order 0.01 solar mass. These small-scale structures traced by CCS appear to be gravitationally unbound by a large factor. Most of these objects have masses that fall below those of the putative proto-brown dwarfs (approx. less than 0.1 solar mass). The presence of many small gravitationally unbound clumps suggests that fragmentation mechanisms other than a purely Jeans gravitational instability may be important for the dynamics of these cold dense cores.
Langer, W. D.↗
Line shape parameters of PH3 transitions: Theoretical studies of self-broadened widths and line mixing effects
Line mixing effects have been calculated in various parallel and perpendicular bands of self-broadened PH3 lines and compared with recent experimental data. The theoretical approach is an extension to symmetric tops with high inversion barrier of the formalism previously developed for NH3 [Q. Ma and C. Boulet, J. Chem. Phys. 144, 224303 (2016)]. The model takes into account the non-diagonality of the scattering operator within the line space as well as, in a correct way, the double degeneracy of the j, k levels when k ≠ 0. Transitions between such levels should be considered as doublets whose components may be coupled by the line mixing process. It has been shown that, at low pressure, the inversion of the experimental data will strongly depend on the splitting between the two components of a doublet. When it is significant, one can measure independently both the width of one component and the intra-doublet coupling matrix element. Otherwise, one can only measure the sum of these two elements. Comparisons with measurements show that the present formalism leads to accurate predictions of the experimental line shapes.
Remote sensing↗
Results of Detailed Modeling of the Narrow-Line Region of Seyfert Galaxies
We present model line profiles of [O II] lambda3727, [Ne III] lambda3869, [O I] lambda5007, [Fe VII] lambda6087, [Fe X] lambda6374, [O I] lambda6300, H(alpha) lambda6563, and [S 2] lambda6731. The profiles presented here illustrate explicitly the pronounced effects that collisional de-excitation, and that spatial variations in both the ionization parameter and cloud column density, have on Narrow-Line Region (NLR) model profiles. The above effects were included only qualitatively in a previous analytical treatment by Moore and Cohen. By making a direct correspondence between these model profiles and the analytical model profiles of Moore and Cohen, and by comparing with the observed profiles presented in a companion paper and also with those presented elsewhere in the literature, we strengthen some of the conclusions of Moore and Cohen. Most notably, we argue for constant ionization parameter, uniformly accelerated outflow of clouds that are individually stratified in ionization, and the interpretation of emission-line width correlations with ionization potential as a column density effect. For comparison with previous observational studies, such as our own in a companion paper, we also calculate profile parameters for some of the models, and we present and discuss the resulting line width correlations with critical density (n(sub cr)) and Ionization Potential (IP). Because the models we favor are those that produce extended profile wings as observed in high spectral resolution studies, the line width correlations of our favoured models are of particular interest. Line width correlations with n(sub cr) and/or IP result only if the width parameter is more sensitive to extended profile wings than is the Full Width at Half-Maximum (FWHM). Correlations between FWHM and n(sub cr) and/or IP result only after convolving the model profiles with a broad instrumental profile that simulates the lower spectral resolution used in early observational studies. The model in agreement with the greatest number of observational considerations has electron density decreasing outward from n(sub e) approx. equals 10(exp 6)/cu cm to n(sub e) approx. equals 10(exp 2)/cu cm and, due to collisional de-excitation effects in the lowest velocity clouds, it generates broad flat-topped profile peaks in the lines of lowest critical density (e.g., [O II] lambda3727 and [S II] lambda(lambda)6716, 6731). Because the observed profile peaks of both low and high critical density lines are often very similar, our favored model requires a contribution to NLR emission-line spectra from low-velocity, low-density, and low-ionization gas not included in the model NLR.
Moore, David↗