Sodium Lines Research Articles

Conical bubble sonoluminescence for water produced by a conical bubble straight tube

A conical bubble straight tube apparatus has been set up to study sonoluminescence for water. The single optical flash produced by the straight tube consists of several bundles of light pulses spreading within 3000 µs. The achieved spectrum consists in a broad continuum background that is well matched by 5500 K blackbody radiation, on which two clear bands of spectrum are superimposed. The higher value of bubble volume probably accounts for the good fit to the blackbody emission. In addition, the resonance line and satellite band of sodium have been detected in water saturated with sodium chloride. Results show that the sodium chloride causes great disturbance to the blackbody radiation for conical bubble luminescence.

Theoretical calculation of population on excited level of emitting atomic species in water plasma

In this work, theoretical study of laser induced plasma spectral emission has been developed. A model based on equilibrium equations has been proposed for the computation of the plasma composition; species densities evolution and excited levels population in the plasma induced on MgCl2-NaCl aqueous solution, are presented alongside temperature range 6000-20 000K. Maximums of excited levels population have been found at distinct temperatures for magnesium and sodium lines. This study has clarified the temperature dependence of the plasma spectral emission.

Observation and modelling of main sequence star chromospheres

Aims. We report on high resolution observations of chromospheric lines for M and K dwarfs. Methods. We observed up to 13 spectral lines per star: the Hα ,H β ,H � ,P a � ,P a 8, CaII H, CaII IR triplet, CaI 6572A, NaI D1/D2 and HeI D3 lines. We observed two dMe stars, one dM(e) star, 5 dM stars and 3 dK stars. Results. We observed a self-reversal in the emission core of the CaII H line for the brightest stars only, indicating a rather optically thick region of formation. We present original spectra of the NaI doublet and the CaII IR triplet for active dMe stars and less active dM stars. Core emission is detected in the Sodium lines and the CaII IR triplet lines for the most active M dwarf AU Mic. We investigate the difference spectra between active dMe stars and dM stars and show that these provide interesting new constraints for the NLTE-radiation transfer modelling of the chromospheres. In our sample, emission Hα profiles have a rather homogeneous FWHM of about 1.5 A. This, according to our previous modelling, can be interpreted as the signature of a rather constant temperature break in the chromosphere. We found that one of our targets (MCC 332) is a binary with a faint but active Hα emission component. – –

Thermal-Hydraulic Challenges in Fast Reactor Design

Thermal-hydraulic challenges in the design of the following four Generation IV fast reactor concepts are presented: sodium [sodium-cooled fast reactor (SFR)], lead [lead-cooled fast reactor (LFR)], gas [gas-cooled fast reactor (GFR)], and liquid salt [liquid salt-cooled fast reactor (LSFR)]. The supercritical carbon dioxide Brayton cycle in indirect mode is the candidate power cycle for all coolants except gas, which is direct cycle. Thermal-hydraulic considerations must be closely integrated with neutronic analysis to properly control reactivity feedbacks, particularly that of the coolant density coefficient. The thermal-hydraulic performance of all reactors is compared to the sodium concept, which has superior performance because of the inherent properties of sodium. The chemical incompatibility of sodium with water and air remains a concern, should a steam generator tube or other sodium line leak. Challenges in steady-state operation, transient performance, shutdown heat removal, and loss-of-coolant-accident design accommodation in gas reactors are reviewed.

Detection of a southern peak in Mercury's sodium exosphere with the TNG in 2005

A long term plan of observations of the sodium exosphere of Mercury began in 2002 by using the high resolution echelle spectrograph SARG and a devoted sodium filter at the 3.5 m Galileo National Telescope (TNG) located in La Palma, Canary Islands. This program is meant to investigate the variations of the sodium exosphere appearance under different conditions of observations, namely Mercury's position along its orbit, phase angle and different solar conditions, as reported by previous observations in August 2002 and August 2003 [Barbieri, C., Verani, S., Cremonese, G., Sprague, A., Mendillo, M., Cosentino, R., Hunten, D., 2004. Planet. Space Sci. 52, 1169–1175; Leblanc, F., Barbieri, C., Cremonese, G., Verani, S., Cosentino, R., Mendillo, M., Sprague, A., Hunten, D., 2006. Icarus 185 (2), 395–402]. Here we present the analysis of data taken in June 29th and 30th and in July 1st 2005, when Mercury's true anomaly angle (TAA) was in the range 124–130°. The spectra show particularly intense sodium lines with a distinctive peak in emission localized in the southern hemisphere at mid-latitudes. This seems to be a persistent feature related to consecutive favorable IMF conditions inducing localized enhancements of surface sodium density. The comparison with previous data taken by Potter et al. [Potter, A.E., Killen, R.M., Morgan, T.H., 2002. Meteorit. Planet. Sci. 37 (9), 1165–1172] evidences a surprising consistency of the anti-sunward component, which appears to remain constant regardless of the changing illumination and space weather conditions at Mercury.

Spectral lines of OH radicals and Na atoms in sonoluminescence

With the equations of fluid mechanics, the proper boundary conditions, and the gas properties, we simulate the processes of single-bubble sonoluminescence. The calculation demonstrates the process of the evolution of the radiation energy spectrum with time for bright sonoluminescing bubbles, which clearly shows how the prominence of the OH line near 310 nm gradually merges into the continuous spectral background as the radiation power increases and finally disappears in the spectrum. For the dim bubble, the spectral line of OH radicals or the sodium line near 589 nm is prominent on the spectrum.

TiO and VO broad band absorption features in the optical spectrum of the atmosphere of the hot-Jupiter HD 209458b

Context. The presence of titanium oxide (TiO) and vanadium oxide (VO) gas phase species is searched for in the atmosphere of the hot Jupiter HD 209458b. Aims. We compared a model for the planet’s transmitted spectrum to multi-wavelength eclipse-depth measurements (from 3 000 to 10 000 A), obtained by Sing et al. (2008a) using archived HST-STIS time series spectra. We make use of these observations to search for spectral signatures from extra absorbers in the planet a tmosphere between 6 000 and 8 000 A. Methods. Along with sodium depletion and Rayleigh scattering recently published for this exoplanet atmosphere, an extra absorb er of uncertain origin, redward of the sodium lines, resides in the atmosphere of the planet. Furthermore, this planet has a stratosphere experiencing a thermal inversion caused by the capture of optical stellar flux by absorbers that resides at altitude. Rec ent models have predicted that the presence of TiO and VO in the atmosphere of HD 209458b may be responsible for this temperature inversion. Although no specific TiO and VO spectral band head signatures have been identified unambiguously in the observed spectrum , we suggest here that the opacities of those molecules are possi ble candidates to explain the remaining continuous broad band absorption observed between 6 200 and 8 000 A. To match reasonably well the data, the abundances of TiO and VO molecules are evaluated from ten to one thousand times below solar. This upper limit result is in agreement with expected variations with altitude due to depletion effects such as condensation. Results.

Determining Atmospheric Conditions at the Terminator of the Hot Jupiter HD 209458b

We present a theoretical model fit to the HST STIS optical transit transmission spectrum of HD 209458b. In our fit, we use the sodium absorption line profile along with the Rayleigh scattering by H2 to help determine the average temperature-pressure profile at the planetary terminator and infer the abundances of atomic and molecular species. The observed sodium line profile spans an altitude range of ~3500 km, corresponding to pressures between ~0.001 and 50 mbar in our atmospheric models. We find that the sodium line profile requires either condensation into sodium sulfide or ionization, necessary to deplete atomic sodium only at high altitudes below pressures of ~3 mbar. The depletion of sodium is supported by an observed sudden abundance change, from 2 times solar abundance in the lower atmosphere to 0.2 solar or lower in the upper atmosphere. Our findings also indicate the presence of a hot atmosphere near stratospheric altitudes corresponding to pressures of 33 mbar, consistent with that of the observed dayside temperature inversion. In addition, we find that a separate higher altitude temperature rise is necessary within both the condensation and ionization models, corresponding to pressures below ~0.01 mbar. This hot higher altitude temperature indicates that absorption by atomic sodium can potentially probe the bottom of the thermosphere and is possibly sensitive to the temperature rise linked to atmospheric escape.

Observation of Mercury's sodium exosphere during the transit on November 9, 2006

A rare, but normal, astronomical event occurred on November 9th 2006 (JST) as Mercury passed in front of the Sun from the perspective of the Earth. The abundance of the sodium vapor above the planet limb was observed by detecting an excess absorption in the solar sodium line D 1 during this event. The observation was performed with a 10-m spectrograph of Czerny–Turnar system at Domeless Solar Tower Telescope at the Hida Observatory in Japan. The excess absorption was red-shifted by 10 pm relative to the solar line, and was measured at the dawnside (eastside) and duskside (westside) of Mercury. Between the dawn and dusksides, an asymmetry of total sodium abundance was clearly identified. At the dawnside, the total sodium column density was 6.1×10 10 Na atoms/cm 2, while it was 4.1×10 10 Na atoms/cm 2 at the duskside. The investigation of dawn–dusk asymmetry of the sodium exosphere of Mercury is a clue to understand the release mechanism of sodium from the surface rock. Our result suggests that a thermal desorption is a main source process for sodium vapor in the vicinity of Mercury.

Atomic Transition Probabilities of Sodium and Magnesium. A Critical Compilation

This compilation is the first in a series of updates to a critical compilation published in 1969 [W. L. Wiese, M. W. Smith, and B. M. Miles, Atomic Transition Probabilities, Vol. II: Sodium through Calcium, NSRDS-NBS Vol. 2 (U.S. GPO, Washington, D.C., 1969)]. Atomic transition probabilities have been critically evaluated and compiled for about 11 400 spectral lines of sodium and magnesium (nuclear charge Z=11–12, respectively). The cited values and their estimated uncertainties are based on our consideration of all available theoretical and experimental literature sources. All ionization stages (except for hydrogenic) are covered, and the data are presented in separate tables for each atom and ion. Separate listings are given for “allowed” (electric dipole) transitions, on the one hand, and for “forbidden” (magnetic dipole plus electric and magnetic quadrupole) transitions, on the other. In each spectrum, lines are grouped into multiplets which are arranged in order of ascending lower and upper-level energies, respectively. For each line, the emission transition probability Aki, the line strength S, and (for allowed lines) the absorption oscillator strength fik are given, together with the spectroscopic designation, the wavelength, the statistical weights, and the energy levels of the lower and upper states. The estimated relative uncertainties of the line strength are also indicated, as are the source citations. We introduce a statistical method that we use to estimate these uncertainties for most of the cited transition rates. We only include those lines whose transition rates are deemed sufficiently accurate to qualify as reference values. Short introductions precede the tables for each ion. The general introduction contains a discussion of the principal criteria for our judgments and our method of data selection and evaluation.

Determination of liquefied petroleum flame temperatures using emission spectroscopy

Emission spectroscopy was used in the temperature determination of LPG (liquefied petroleum gas) premixed flames. Natural emission of CH* radicals was investigated in flames under three different burning conditions: fuel/oxydizer stoichiometric ratio, fuel excess (rich flame), and oxidizer excess (lean flame). An average value of 2845 ± 70 K was obtained for CH* rotational temperature in the set up used in the experiments. This value did not show significant change with the type of flame analyzed and it is compatible with the calculated adiabatic flame temperatures of the investigated systems. This temperature value also agrees with that determined by an indirect measurement, using the sodium line reversal method, which is independent from the radical natural emission and well established in literature. Vibrational temperatures of ca. 4600 K were calculated, indicating that the CH* lifetime is insufficient for the establishment of an equilibrium state between the rotational and vibrational modes.

Sonoluminescence of Na Atom from NaCl Solutions Doped with Ethanol

Sonoluminescence spectra from argon-saturated NaCl solution were measured in the concentration range of 0.5-4 M at the frequency of 138 kHz. The line broadening of sodium atom emission was observed at various acoustic powers in the range from 1.8 to 16.2 W. The sodium D line showed a maximum intensity at a NaCl concentration of 2 M, which corresponded to the maximum production of OH radicals estimated by KI dosimetry. The effects of the addition of a small amount of ethanol on the line width and intensity were closely investigated at various acoustic powers. The sodium line width increases with ethanol concentration and also with power, whereas the line intensity is strongly quenched with increasing ethanol concentration. The results conclusively show that the sodium emission occurs in the gas phase within bubbles. The line broadening is due to interactions with high-pressure argon, and the maximum relative density of gas at bubble collapse was estimated to be 59.5 from the comparison with spectroscopic data. Further line broadening and quenching upon the addition of ethanol arise from collisions with gaseous products obtained from the decomposition of ethanol. The mechanism of sodium excitation is inferred to be as follows. Sodium ions enter bubbles as droplets, and salts are formed because of the high temperature within bubbles. Sodium atoms are generated by the dissociation of salts and then undergo electronic excitation by OH and H radicals.

Parametric dependence of the line emissions in sonoluminescence

Based on a series of spectral measurements of sonoluminescence, this paper investigates parametric dependence of the line emissions in single bubble sonoluminescence (SBSL) and multi-bubble sonoluminescence (MBSL). The experiments show that the intensities of the OH radical line, the sodium line and the noble gas lines in SBSL are relevant to the driving pressure of the acoustic field and the concentration of the noble gases dissolved in host liquids. The intensity of line emissions in total spectrum increases with the decreasing driving pressure and the increasing concentration of noble gases. Parametric dependence of line emissions in MBSL consists with that in SBSL. Line emissions in sonoluminescence should correspond to lower temperature inside the bubbles. SBSL and MBSL share the same spectral structure, and the difference between them found by previous experiments should result from the different temperatures inside bubbles.

The Ionization State of Sodium in Galactic Winds

Roughly 80% of Ultraluminous Infrared Galaxies (ULIRGs) show blue shifted absorption in the resonance lines of neutral sodium, indicating that cool winds are common in such objects, as shown by Rupke et al and by Martin. The neutral sodium (NaI) columns indicated by these absorption lines are ~ 10^{13}-3x10^{14}/cm^2, while the bolometric luminosity varies by a factor of only four. We show that the gas in ULIRG outflows is likely to be in photoionization equilibrium. The very small ULIRG sample of Goldader et al. demonstrates that the ratio of ultraviolet flux to far infrared flux varies by a factor $\sim100$ from object to object. While the Goldader sample does not overlap with those of Rupke et al. and Martin, we show that such a large variation in ultraviolet flux will produce a similar variation in the column of neutral sodium for a fixed mass flux and density. However, if the cold gas is in pressure equilibrium with a hot outflow with a mass loss rate similar to the star formation rate, the range of ionization state is significantly smaller. Measurements of the UV flux for objects in the Martin and Rupke et al. catalogs will definitively determine if photoionization effects are responsible for the wide variation seen in the sodium columns. If they are, a determination of the gas density and mass loss rate in the cool winds will follow, with attendant improvements in our understanding of wind driving mechanisms and of the effects of galaxies on their surroundings.

Resonance potassium and sodium lines in the spectra of ultracool dwarfs

We discuss the methodological problems and results of computations of the spectral energy distributions (SEDs) of L dwarfs. Over a wide wavelength interval (λλ4000–10 000 A), the spectra of these stars are determined to a considerable extent by absorption in resonance lines of potassium (7666.961, 7701.031 A) and sodium (5891.518, 5897.489 A). We compute the extended wings of these lines using the theory of quasi-stationary broadening. We compute the cores and nearby wings (up to Δλ = 40 A from the line center) of the KI and NaI lines in a collisional approximation (van der Waals theory). In our modeling of the SED of the ultracool dwarf 2MASS J15232263+3014562 (L8), we find that the observations agree best with the COND atmospheric models of Allard et al. with T eff = 2200 K and log g = 6.0.

First-Principles Simulations on the Nature of the Melting Line of Sodium

We report a first-principles molecular dynamics study of the reentering behavior that has been recently observed experimentally in the melting line of bcc sodium [Gregoryanz et al., Phys. Rev. Lett. 94, 185502 (2005)10.1103/PhysRevLett.94.185502]. Our results show the liquid phase to be more compressible than the solid phase, and to remain so at high pressures, eventually becoming denser than the solid phase and hence causing the change of slope in the melting line from positive to negative. The maximum of the melting line thus occurs without any accompanying first-order liquid-liquid phase transition.

NLTE determination of the sodium abundance in a homogeneous sample of extremely metal-poor stars

Abundance ratios in extremely metal-poor (EMP) stars are a good indication of the chemical composition of the gas in the earliest phases of the Galaxy evolution. It had been found from an LTE analysis that at low metallicity, and in contrast with most of the other elements, the scatter of [Na/Fe] versus [Fe/H] was surprisingly large and that, in giants, [Na/Fe] decreased with metallicity. Since it is well known that the formation of sodium lines is very sensitive to non-LTE effects, to firmly establish the behaviour of the sodium abundance in the early Galaxy, we have used high quality observations of a sample of EMP stars obtained with UVES at the VLT, and we have taken into account the non-LTE line formation of sodium. The profiles of the two resonant sodium D lines (only these sodium lines are detectable in the spectra of EMP stars) have been computed in a sample of 54 EMP giants and turn-off stars (33 of them with [Fe/H]< -3.0) with a modified version of the code MULTI, and compared to the observed spectra. With these new determinations in the range -4 <[Fe/H]< -2.5, both [Na/Fe] and [Na/Mg] are almost constant with a low scatter. In the turn-off stars and unmixed giants (located in the low RGB): [Na/Fe] = -0.21 +/- 0.13 or [Na/Mg] = -0.45 +/- 0.16. These values are in good agreement with the recent determinations of [Na/Fe] and [Na/Mg] in nearby metal-poor stars. Moreover we confirm that all the sodium-rich stars are stars (i.e., giants located after the bump, which have undergone an extra mixing). None of the turn-off stars is sodium-rich. As a consequence it is probable that the sodium enhancement observed in some mixed giants is the result of a deep mixing.

Planar temperature imaging using thermally assisted laser induced fluorescence of OH in a methane–air flame

The present study seeks to demonstrate the use of vibrational thermally assisted laser induced fluorescence of the hydroxyl radical to obtain planar temperature measurements. This technique utilizes a simple two-level vibrational model to describe the relationship between the population ratio of excited states and temperature. The quenching to vibrational transfer ratio between the excited states was used as a calibration parameter to fit the thermally assisted fluorescence measurements to known temperature data. The measurements presented here are from a premixed methane–air flame. A rectangular shaped burner allowed for calibration and comparison of the thermally assisted temperature results with sodium line reversal data available in literature. Excellent agreement between the two approaches was achieved for three different equivalence ratios. A single calibration was sufficient for the range of conditions tested in the present work. Two detection schemes were also tested, the first using the (0–0) and (1–0) vibrational bands and the second substituting the (0–1) fluorescence in place of the (0–0) band. The weakness of the fluorescence signal from the (0–1) band was very restrictive to temperature imaging with the current setup. Overall, the applicability of the thermally assisted technique to temperature imaging was positively demonstrated from this work.

Theoretical study of sodium and potassium resonance lines pressure broadened by helium atoms

We perform fully quantum mechanical calculations in the binary approximation of the emission and absorption profiles of the sodium $3s\text{\ensuremath{-}}3p$ and potassium $4s\text{\ensuremath{-}}4p$ resonance lines under the influence of a helium perturbing gas. We use carefully constructed potential energy surfaces and transition dipole moments to compute the emission and absorption coefficients at temperatures from $158\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}3000\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. Contributions from quasibound states are included. The resulting red and blue wing profiles agree well with previous theoretical calculations and with experimental measurements.

Suppression of Rayleigh scattering noise in sodium laser guide stars by hyperfine depolarization of fluorescence

We propose what we believe is a novel method for enabling the complete suppression of noise due to Rayleigh scattering in sodium laser guide star systems by means of selective discrimination between Rayleigh and fluorescence signals based on polarization properties. We show that, contrary to the nearly 100% polarized Rayleigh scattering, fluorescence from the D(2) sodium line is strongly depolarized under excitation by a modeless laser. This offers the possibility of completely cancelling the effects of the Rayleigh scattering background while preserving the fluorescence signal to about 40% of its maximal value, leading to an improvement of the signal-to-noise ratio by several orders of magnitude. Both theoretical and experimental data confirm this new proposal.