Precision Fe i and Fe ii wavelengths in the ultraviolet spectrum of the iron–neon hollow-cathode lamp

Nave, Gillian; Learner, R. C. M.; Thorne, Anne P.; Harris, Christopher

doi:10.1364/josab.8.002028

Cited by 70 publications

(86 citation statements)

References 11 publications

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“…wavelength:-(L) Pickering et al (1998); (M) Griesmann & Kling (2002); (P) Pickering et al (2002); (Q) Nave et al (1991). interpolated weighted mean errors and possible errors due to scatter in the individual flux measurements.…”

Section: Observations and Data Samplementioning

confidence: 99%

Probing the cosmological variation of the fine-structure constant: Results based on VLT-UVES sample

Chand

Srianand

Petitjean

et al. 2004

A&A

262

333

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Abstract. Development of fundamental physics relies on the constancy of various fundamental quantities such as the finestructure constant. Detecting or constraining the possible time variations of these fundamental physical quantities is an important step toward a complete understanding of basic physics. High-quality absorption lines seen in the spectra of distant QSOs allow one to probe time variations of several of these quantities. Here we present the results from a detailed manymultiplet analysis, to detect the possible variation of the fine-structure constant, performed using high signal-to-noise ratio, (∼70 per pixel), high spectral resolution (R ≥ 45 000) observations of 23 Mg  systems detected toward 18 QSOs in the redshift range 0.4 ≤ z ≤ 2.3 obtained using UVES at the VLT. We validate our procedure and define the selection criteria that will avoid possible systematics using a detailed analysis of a simulated data set. The spectra of Mg  doublets and Fe  multiplets are generated considering variations in α and specifications identical to that of our UVES spectra. We show that our Voigt profile fitting code recovers the variation in α very accurately when we use single component systems and multiple-component systems that are not heavily blended. Spurious detections are frequently seen when we use heavily blended systems or systems with very weak lines. Thus we avoided these system while analysing the UVES data. To make the analysis transparent and accessible to the community for critical scrutiny, all the steps involved in the analysis are presented in detail. The weighted mean value of the variation in α obtained from our analysis over the redshift range 0.4 ≤ z ≤ 2.3 is ∆α/α = (−0.06 ± 0.06) × 10 −5 . The median redshift of our sample is 1.55 and corresponds to a look-back time of 9.7 Gyr in the most favored cosmological model today. The 3σ upper limit on the time variation of α is −2.5 × 10 −16 yr −1 ≤ (∆α/α∆t) ≤ +1.2 × 10 −16 yr −1 . To our knowledge this is the strongest constraint from quasar absorption line studies to till date.

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Section: Observations and Data Samplementioning

confidence: 99%

Probing the cosmological variation of the fine-structure constant: Results based on VLT-UVES sample

Chand

Srianand

Petitjean

et al. 2004

A&A

262

333

View full text Add to dashboard Cite

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“…The corresponding calibration uncertainties used in our analysis of the silver lines are 0.004 cm-~ at 206.1 nm and 0.0016 cm-J at 547.5 nm for the diffraction orders used. Uncertainties due to residual source shifts, such as pressure shifts, Doppler shifts or self-absorption effects, are expected to be smaller than the above values [10]. …”

Section: Calibration Of Wavelength Scansmentioning

confidence: 79%

“…The lamp was operated with a (square-wave) modulated current of 5mA for the 206.1 nm line and 10mA for the 547.5 nm line. A commercial (Varian-Techtron) neonfilled iron hollow-cathode discharge lamp provided reference lines of iron [ 10,11] for accurate wavelength calibration of the monochromator scans.…”

Section: Light Sourcesmentioning

confidence: 99%

“…The iron reference lines selected for wavelength calibration of the silver lines are listed in Table 1, along with the vacuum wavenumbers reported by Nave et al [10] and O'Brian et al [ 11 ]. The wavenumbers for these two independent sets of measurements were calibrated against ArlI lines (accuracy 0.0003 cm -1) measured interferometrically by Norl6n [16].…”

Section: Calibration Of Wavelength Scansmentioning

confidence: 99%

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Precision measurement of the energy of the 4d 9 5s 2 2 D 5/2 metastable level in Ag I

Larkins

Hannaford

1994

Z Phys D - Atoms, Molecules and Clusters

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Abstract. The energy of the 4d95s22Ds/2 metastable level in Ag I, which is the upper level of the very narrow 5 s 2S1/2-4 d 9 5 s 22D5/2 two-photon transition at 661.2 nm, has been determined from precision measurements of the wavelengths of the 206.1 nm (5s2S1/2-6p2P°/2) and 547.5nm (4d9 5s22Ds/2-6p 2P°/2 ) lines emitted from a hollow-cathode discharge. The measured energy of the 4 d 9 5 s 2 2D5/2 level, 30242.286(7) cm -~, is combined with the known hyperfine splittings and the estimated l°7Ag-l°9Ag isotope shift to obtain accurate absolute frequencies for the hyperfine components of the 661.2 nm transition. These results should help in the detection of the narrow 661.2 nm twophoton transition, which has been proposed as a new optical frequency standard. PACS: 32.30Jc; 35.10.Fk I. ln~oducfionThere is currently much interest in the spectroscopy of the Ag I 5s 2S1/2-4d 9 5s 2 2D5/2 two-photon transition at 661.2nm [1][2][3][4] involving the long-lived (~0.2s [5,6]) 4d95s 2 2D5/2 metastable level, which decays by electric quadrupole radiation at 330.6nm. Because of its extremely small natural linewidth (g0.8 Hz), the 5s2S~/2-4d95s22Ds/2 transition when driven by the 661.2 nm Doppler-free two-photon transition in a beam or atomic fountain of laser-cooled silver atoms is a particuiarly attractive candidate for an optical frequency standard [2,3]. However, in order to be able to detect such a narrow two-photon resonance, it is important first to know the absolute frequency of the very weak Tables [9], and these are found to yield resuits that differ by up to 0.5cm -a, or 15GHz (see Table 3). Attempts in this laboratory to detect the very weak 330.6 nm E2 transition in high resolution scans of the emission from a silver hollow-cathode lamp have to date proven to be unsuccessful. In this paper we report a pre-

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“…There are many atomic iron (Fe I) emission lines in the wavelengths examined by these methods [77]. These have been previously observed in other hypersonic flow conditions [78].…”

Section: Results From Optical Techniquesmentioning

confidence: 74%

Experimental Investigation of a 3D Thermal Compression Scramjet Using Advanced Optical Techniques

Vanyai¹

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Scramjet engines are limited in performance due to engine starting problems at low hypersonic speeds. For an accelerating hypersonic vehicle, intake contraction ratios are typically fixed to the low speed starting requirements. This reduces engine performance at higher Mach numbers, where higher contraction ratios are required to efficiently combust flow within a practically-sized combustor.The use of a combustion process called "Thermal Compression" was suggested in the 1960s that could improve the performance of low intake contraction scramjet engines. In such an engine, the flow field is non-uniform within the combustor, with regions of locally high pressure and temperature even at low net intake contraction ratio. The flow properties in these regions are suitable for combustion of air-fuel mixtures, inducing autoignition. As heat is released, increased temperature and pressure are transmitted to the surrounding flow through pressure waves. Conditions in the surrounding flow become suitable for combustion, and this process continues until combustion completes throughout the entire flow field.This work presents results from experimental and numerical analysis of a three-dimensional, thermal compression scramjet engine at two high Mach number flight conditions. Experiments were conducted in the T4 Shock Tunnel at The University of Queensland. The tunnel test gas simulated flow that had been processed by an engine forebody at either 8.0• or 8.8• angle of attack, in an equivalent flight condition of Mach 10, 50 kPa dynamic pressure.An engine test model was developed to examine the effect of thermal compression on combustion-induced pressure rise at these inflow conditions. Non-uniform combustor flow was generated using a three-dimensional intake with a ramp angle that varied in the spanwise direction. This produced a low compression side and a high compression side throughout the scramjet engine. Fuel injection plenums were split such that different gases could be injected in either the low compression or high compression side. Combustion was induced by injecting hydrogen fuel, or suppressed by injecting helium.i Pressure measurements were taken along the streamwise length of the engine, in three spanwise locations. Optical techniques, including emission and laser-induced fluorescence (LIF) methods, were used to visualise the distribution of OH radicals throughout the combustor. These experimental results were then compared to fully-combusting, RANS CFD simulations.The influence of thermal compression was determined by comparing combustion-induced pressure rise in the fully-fuelled case to the sum of both cases where combustion was suppressed on each side of the engine. It was found that for the forebody angle of 8.8• case, thermal compression increased pressure rise by 14.4 ± 6.0 % and 6.7 ± 6.2 % for fuel-air equivalence ratios of φ = 0.8 and φ = 1.0 respectively. Emission from OH radicals, which is qualitatively indicative of combustion, also increased by 19 -54 % in the rear of the combustor. Numerica...

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Precision Fe i and Fe ii wavelengths in the ultraviolet spectrum of the iron–neon hollow-cathode lamp

Cited by 70 publications

References 11 publications

Probing the cosmological variation of the fine-structure constant: Results based on VLT-UVES sample

Probing the cosmological variation of the fine-structure constant: Results based on VLT-UVES sample

Precision measurement of the energy of the 4d 9 5s 2 2 D 5/2 metastable level in Ag I

Experimental Investigation of a 3D Thermal Compression Scramjet Using Advanced Optical Techniques

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