Spectrophysics

Thorne, Anne P.

doi:10.1007/978-94-009-1193-2

Cited by 288 publications

(271 citation statements)

References 0 publications

Supporting

Mentioning

258

Contrasting

Unclassified

Order By: Relevance

“…where g u and g l are the statistical weights for the upper and lower level respectively, λ is the wavelength in Å, A ul is in s −1 , and log(g l f ) has been abbreviated to log(g f ) for the general usage in this paper, see Thorne et al (1999), Huber & Sandeman (1986).…”

Section: Oscillator Strengthsmentioning

confidence: 99%

Experimental Ca I oscillator strengths for the 4p–5s triplet

Aldenius¹,

Lundberg

Blackwell-Whitehead³

2009

A&A

View full text Add to dashboard Cite

Context. Transition lines of neutral calcium are observed in the spectra of stellar and substellar objects. In particular, the abundance of α-elements in metal-poor stars can place important constraints on the galactic chemical evolution. Such stellar abundance analyses rely heavily on accurate values for the oscillator strength of the observable transitions. Theoretical oscillator strengths are available for most neutral calcium lines visible in stellar spectra, but there are a limited number of experimental values in the literature.Aims. We present new and improved experimental oscillator strengths for the optical Ca i 4p-5s triplet (6102.7, 6122.2, 6162.2 Å). In addition, we present experimental radiative lifetimes for seven energy levels in the triplet system of Ca i.Methods. The oscillator strengths were determined by combining radiative lifetimes with branching fractions. The radiative lifetimes were measured using laser-induced fluorescence, and the branching fractions were determined using intensity calibrated spectra measured with Fourier transform spectrometry. In addition, the spectra were used to determine accurate (dλ = 0.001 Å, dσ = 0.002 cm −1 ) laboratory wavelengths for the 4p-5s transitions.Results. Oscillator strengths for the Ca i 4p-5s lines were determined with an absolute uncertainty of 9%, an uncertainty of ±0.04 dex in the log(g f ) values. The branching fractions were determined with a higher accuracy, resulting in relative uncertainties of 2-3%.

show abstract

Section: Oscillator Strengthsmentioning

confidence: 99%

Experimental Ca I oscillator strengths for the 4p–5s triplet

Aldenius¹,

Lundberg

Blackwell-Whitehead³

2009

A&A

View full text Add to dashboard Cite

show abstract

“…The most general method uses the area under the fractional absorption to compute the equivalent width, which is conserved regardless of instrumental linewidth. The equivalent width is then used with the curve of growth method 6 to obtain accurate density results even for strongly absorbed narrow lines, which appear to have small fractional absorptions because of the large difference between the spectral ͑0.005 nm͒ and instrumental ͑0.01 nm͒ linewidths. The absorbance method is also independent of instrumental resolution, but underestimates the density for strongly absorbing spectral lines.…”

Section: Density Calculations For Optical Absorption Measurementsmentioning

confidence: 99%

Absolute densities of long lived species in an ionized physical vapor deposition copper–argon plasma

Andrew

Abraham

Booske

et al. 2000

Journal of Applied Physics

View full text Add to dashboard Cite

Optical absorption spectroscopy has been used to measure absolute, average gas phase densities of neutral copper, ground and metastable states, and neutral argon, metastable and resonance states, in an ionized physical vapor deposition plasma. Spectroscopic measurements were carried with a xenon arc lamp as a high intensity, continuum light source, and an optical multichannel detector. Copper radiative transitions in the wavelength range of 324.8-510.6 nm and argon radiative transitions in the 706.7-811.5 nm range were employed. The curve of growth method has been used to calculate the absolute line average densities from fractional absorption data. For a copper-argon plasma of neutral pressure 30 and 10 mTorr copper metastable state densities were found to lie in the range of 10 10 -10 12 cm Ϫ3 . Comparison of these densities with neutral copper densities derived from independent measurements of neutral copper flux at the substrate indicate gas phase temperatures greater than 1500 K under certain experimental conditions. These values of inferred temperatures indicate the copper metastable state density to be significant in comparison with neutral copper ground state densities at 10 and 30 mTorr with radio frequency heating power of 1 kW. The concentrations of argon 4s sublevels of the first excited state were found to be in the range of 4.5ϫ10 8 -1.5ϫ10 11 cm Ϫ3 for the experimental conditions studied. The ordering of the relative densities of the argon 4s sublevels and the variation of the lumped first excited state with experimental parameters are discussed.

show abstract

“…light is readily absorbed) the emission spectrum is continuous and uniquely dependent on temperature. Such media can be approximated by a blackbody -the perfect emitter and absorber; radiance of spectral emission is described by Planck's blackbody distribution [25]:…”

Section: Driver Gas Spectroscopymentioning

confidence: 99%

“…The line spectra generated from transition of atoms between discrete energy levels in a radiating gas tends to be an opposite extreme to the continuous blackbody radiation curves, as the optical density of the radiating gas decreases [25]. For an optically thin species (i.e.…”

Section: Driver Gas Spectroscopymentioning

confidence: 99%

“…Nhc U = constant) [19]: T ex = E m − E p −k ln ( I mn g m A mn λ p I pn g p A pn λ m ) Validity of the method requires: (i) local thermal equilibrium (LTE) to exist, i.e. where de-excitation due to collision is more likely than due to spontaneous emission, (ii) a sufficiently wide range for E and hence λ [19,25] and (iii) background emission to be adequately excluded from the intensities of the two transitions [26,27].…”

Section: Driver Gas Spectroscopymentioning

confidence: 99%

See 1 more Smart Citation

X3 expansion tube driver gas spectroscopy and temperature measurements

et al. 2017

View full text Add to dashboard Cite

The University of Queensland's X3 facility is a large, free-piston driven expansion tube used for superorbital and high Mach number scramjet aerothermodynamic studies. X3's powerful test flow is initiated by firing its heavy piston into its driver gas -a mixture of argon and helium. Knowledge of the initial and transient temperature behavior of the driver gas is critical to correctly characterize the driver performance, losses and all subsequent expansion tube flow processes. However, the driver gas temperature is not currently measured during routine experimentation and there is limited evidence of its measurement in other international facilities. During recent scramjet flow development in X3, lower than expected experimentally measured shock speeds through helium indicated an effective driver temperature of approximately 2400 K, compared to a temperature of 3743 K at the time of diaphragm rupture for an ideal isentropic driver gas compression. These performance losses motivate this study, which examines initial and peak driver gas temperatures. The study shows that the initial steady-state driver gas temperature, once the filling process ceases, can be approximated by the external driver tube wall temperature. During filling, a net increase in driver gas temperature occurs due to compression heating, as well as, Joule-Thomson effect for helium. Optical emission spectroscopy was then used to resolve the peak driver gas temperature, during piston compression, for a Mach 10 scramjet operating condition. The driver gas emission spectrum exhibits a significant background radiation component, with prominent spectral lines attributed to contamination of the flow. A blackbody approximation of background radiation suggests a peak driver gas temperature of 3200±100 K. Application of the line-ratio method to two argon lines at 763.5 and 772.4 nm suggests a temperature of 3500±750 K. Comparison of these estimates to the ideal isentropic driver gas temperature at diaphragm rupture, 3743 K, suggests losses in the driver gas temperature during the compression process are not extensive for X3, and further that the lower than expected shock speeds are likely primarily due to pressure losses during driver gas expansion through the diaphragm and at the driver-to-driven tube area change. Nomenclature A = Einstein coefficient for spontaneous emission, s -1 a = sound speed, m/s c = speed of light = 3×10 8 m/s E = energy of the upper atomic state, eV g = statistical weight of upper atomic state h = Planck's constant = 4.136×10 -15 eV.s I = spectral intensity, counts K = Boltzmann's constant = 8.617×10 -5 eV/K L = spectral radiance, W/m 2 /sr/nm M = molecular weight, g/mol P i = driver gas initial pressure, Pa P p = driver gas pressure at rupture, Pa R = gas constant, J/mol/K T abs = absolute temperature, K T ex = excitation temperature, K T i = driver gas initial temperature, K T p = driver gas average peak temperature, K γ = ratio of specific heats λ = wavelength, m 1 Undergraduate, School of Mechanical and Mining Engineering, AIA...

show abstract

Spectrophysics

Cited by 288 publications

References 0 publications

Experimental Ca I oscillator strengths for the 4p–5s triplet

Experimental Ca I oscillator strengths for the 4p–5s triplet

Absolute densities of long lived species in an ionized physical vapor deposition copper–argon plasma

X3 expansion tube driver gas spectroscopy and temperature measurements

Contact Info

Product

Resources

About