The absorption of light by calcium vapour (2100 to 1080 Å)

1960 ◽  
Vol 256 (1284) ◽  
pp. 53-61 ◽  
Keyword(s):  
Short Wavelength ◽  
Absorption Lines ◽  
Continuous Absorption ◽  
Absorption Of Light ◽  
Line Absorption ◽  
Short Wavelength Side ◽  
No Absorption ◽  
Wavelength Side

Continuous absorption and line absorption of radiation in calcium vapour has been measured from the 4 s 4 s 1 S 0 → 4 snp 1 P 1 series limit at 2028 to 1080 Å. Two perturbed series of auto-ionization lines (4 s 4 s 1 S 0 → 3 dnp 1 P 1 and → 3 dnp 3 P 1 ) are recorded and analyzed. A second series limit is observed at 1589 Å. This is probably two unresolved limits corresponding to the two series of auto-ionization lines. No absorption lines are observed on the short wavelength side of 1589 Å. The f -values of the lines vary from 2.4 x 10 -2 to 6 x 10 -5 and the half-lives (calculated from measurements of the half-widths of the lines) vary from 30 to 260 x 10- 15 s. The f -value for the 4 s 4 s 1 S 0 → 4 snp 1 P 1 continuum is estimated to be 0.012 (including an allowance for a portion below 1589 Å) and the f -value for the continua from wavelength 1589 to 1080 Å corresponding to the two series of auto-ionization lines is estimated to be 0.003. The measured value of the absorption near 2028 Å is about one-fiftieth of the theoretical value which has been used in astrophysical calculations.

scholarly journals Röntgenspektroskopische Untersuchung der chemischen Bindung in Oxiden

1967 ◽  
Vol 22 (9) ◽  
pp. 1401-1407 ◽  
Author(s):  
Hans-Ulrich Chun ◽  
Dieter Hendel
Keyword(s):  
Fine Structure ◽  
Metal Atom ◽  
Short Wavelength ◽  
The Other ◽  
Main Line ◽  
Ionic Character ◽  
Long Wavelength ◽  
Short Wavelength Side ◽  
Oxygen Bond ◽  
Wavelength Side

This paper reports about the fine structure in the O—K-spectra of the oxides BeO, MgO, CaO, SrO, BaO, Sc2O5, Y2O3, La2O3, Sm2O3, Yb2O3, NiO and ZnO. The spectra show the satellite lines α3, α4, α5, α6 on the short wavelength side of the main line α1,2 and a shoulder β′ on its long wavelength side. The wavelengths of all lines depend on the nature of the oxide. For the positions of the lines Kα1.2 in the spectra no systematic relation to other data of the oxides is observed. On the other hand the distance of the a4-satellite from the α1,2-line decreases with increasing electronegativity of the metal atom in the oxide. This distance can be used as a measure for the ionic character of the metal-oxygen bond in these compounds.

Mass Loss from Stars

1977 ◽  
Vol 3 (2) ◽  
pp. 96-96
Author(s):  
Donald C. Morton
Keyword(s):  
Mass Loss ◽  
Radiation Field ◽  
Excited States ◽  
Short Wavelength ◽  
Hot Stars ◽  
Short Wavelength Side ◽  
Far Ultraviolet ◽  
Wavelength Side ◽  
Space Observations

The visual spectra of some hot stars, including P Cygni, have emission with associated absorption troughs ˜ 102 km s-1 on the short-wavelength side (Beals 1929, 1951). These P Cygni profiles are easily understood in terms of mass flowing away from the star. Later, rocket observations of the far-ultraviolet resonance lines (Morton 1967) showed that the phenomenon is rather common among hot stars and the velocity shifts could be from 1000 to 3000 km s-1, demonstrating that the mass must be escaping from the star. Resonance lines provide the strongest absorption in the shell where neither the density nor the radiation field is high enough to leave many ions in excited states. Since the ion stages likely to be present around a hot star have their resonance lines shortward of the atmospheric cutoff, space observations are essential in this investigation. Figure 1 shows the P Cygni profile of O VI in ς Pup obtained with Copernicus satellite spectrometer.

A Discussion on astronomy in the ultraviolet - Mass loss from the A-type supergiant α Cygni

1975 ◽  
Vol 279 (1289) ◽  
pp. 445-450 ◽  
Keyword(s):  
Mass Loss ◽  
Spectral Resolution ◽  
Short Wavelength ◽  
High Spectral Resolution ◽  
The Core ◽  
Short Wavelength Side ◽  
Wavelength Side

The Mg ii resonance lines in a Cygni (A2Ia) are studied from 22 spectral scans obtained by the experiment S59. The cores of the resonance lines are shifted by — 130 km/s and the short wavelength side of the core is shifted by about — 350 km/s. The lines are compared with predicted profiles in an expanding atmosphere. This comparison suggests a rate of mass loss of 3 x 10-10 ^®/year. The atmosphere seems to be accelerated up to a velocity of 300 km/s. The acceleration might be produced by the near-u.v. resonance lines of singly ionized metals. The observations of the near-u.v. spectrum of A-type supergiants with a high spectral resolution is recommended.

Pragmatic Tyre Model for Short Wavelength Side Slip Variations

1999 ◽  
Vol 31 (2) ◽  
pp. 65-94 ◽  
Author(s):  
J.P. Maurice ◽  
M. Berzeri ◽  
H.B. Pacejka
Keyword(s):  
Short Wavelength ◽  
Tyre Model ◽  
Short Wavelength Side ◽  
Wavelength Side

scholarly journals On the absorption of light by crystals

1938 ◽  
Vol 167 (930) ◽  
pp. 384-391 ◽  
Keyword(s):  
Absorption Spectrum ◽  
Wave Length ◽  
Short Wave ◽  
Point Of View ◽  
Theoretical Point ◽  
Lattice Vibrations ◽  
Short Wave Length ◽  
Continuous Absorption ◽  
Absorption Of Light ◽  
Positive Hole

The purpose of this paper is to discuss the absorption of light by non-metallic solids, and in particular the mechanism by which the energy of the light absorbed is converted into heat. If one considers from the theoretical point of view the absorption spectrum of an insulation crystal, one finds that it consists of a series of sharp lines leading up to a series limit, to the short wave-length side of which true continuous absorption sets in (Peierls 1932; Mott 1938). In practice the lattice vibrations will broaden the lines to a greater of less extent. When a quantum of radiation is absorbed in the region of true continuous absorption, a free electron in the conduction band and a "positive hole" are formed with enough energy to move away from one another and to take part in a photocurrent within the crystal. When, however, a quantum is absorbed in one of the absorption lines , the positive hole and electron formed do not have enough energy to separate, but move in one another's field in a quantized state. An electron in a crystal moving in the field of a positive hole has been termed by Frenkel (1936) an "exciton".

The continuous absorption of light in alkali-metal vapours

1953 ◽  
Vol 219 (1136) ◽  
pp. 89-101 ◽  
Keyword(s):  
Cross Section ◽  
Alkali Metals ◽  
Theoretical Calculations ◽  
Wave Length ◽  
Energy Difference ◽  
Continuous Absorption ◽  
Absorption Of Light ◽  
Sodium Vapour ◽  
Good Agreement ◽  
Dipole Length

The first section of this paper is an account of some experiments on the absorption of light in sodium vapour from the series limit at 2412 Å to about 1600 Å (an energy difference of 2·6 eV). The absorption cross-section at the limit is 11·6 ± 1·2 x 10 -20 cm 2 . The cross-section decreases giving a minimum of 1·3 ± 0·6 x 10 -20 cm 2 at 1900 Å and then increases to 1600 Å. A theoretical calculation by Seaton based on the dipole-length formula gives good agreement with the experiments at the series limit and also correctly predicts the wave-length for the minimum, but it predicts a significantly lower absorption at the minimum. The experiments described in the first section of the paper conclude a series on the absorption of light in the alkali metals. The second section consists of a general discussion of the results of these experiments and of their relation to theoretical calculations. There is good agreement between theory and experiment except in regard to the magnitude of the absorption at the minimum.

The absorption spectra of irradiated diamonds after heat treatment

1956 ◽  
Vol 237 (1208) ◽  
pp. 75-89 ◽  
Keyword(s):  
Absorption Spectra ◽  
Absorption Lines ◽  
Type I ◽  
Type Ii ◽  
Large Reduction ◽  
Isothermal Heating ◽  
Interstitial Carbon ◽  
Crystal Imperfections ◽  
Continuous Absorption ◽  
Kinetics Of

The absorption spectra of eight type I and three type II a diamonds irradiated with neutrons, electrons or y-rays have been recorded at 80 and 290°K after various heat treatments in the temperature range 0 to 900°C. It is found that heating in the range 350 to 450°C causes a general reduction in the irradiation-induced absorption owing to the recombination of those interstitials and vacancies which are near neighbours. Heating type II a diamonds at 600°C causes a large reduction in the irradiation-induced lines and new lines appear. These are probably due to pairs of identical defects, and the kinetics of their formation during isothermal heating at 600°C are presented. At higher temperatures all absorption lines in type II a diamonds disappear and only continuous absorption remains. This is probably due to amorphous or graphitic regions produced by agglomeration of defects. Type I diamonds show the same kind of absorption, but in addition show an increase in strength of the natural lines and also some new absorption lines which are not removed by heating at 900°C. It is suggested that these additional processes are due to the anchoring of vacant atomic sites and interstitial carbon atoms at crystal imperfections present only in type I diamonds.

scholarly journals 19. Astrophysical applications of selective magnetic rotation

1958 ◽  
Vol 6 ◽  
pp. 166-168
Author(s):  
Y. öhman
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Zeeman Effect ◽  
Emission Lines ◽  
Absorption Lines ◽  
Magnetic Rotation ◽  
Double Refraction ◽  
Line Absorption ◽  
Complicated Process ◽  
The Magnetic Field

When measuring the magnetic fields of sunspots the astronomer assumes that the magnetic field revealed by the inverse Zeeman effect is the same as if the splitting were produced by emission lines instead of absorption lines. No doubt this is in general a very fair approximation, but we have reason to remember sometimes that line absorption in the presence of magnetic fields is a very complicated process. In the immediate neighbourhood of absorption lines effects of magnetic rotation of the plane of polarization and magnetic double refraction may appear in the spectrum.

scholarly journals Influence of the Stellar Wind on the Nebular Ionization in NGC 1535 and 4361

1983 ◽  
Vol 103 ◽  
pp. 338-339
Author(s):  
J. Adam ◽  
J. Köppen
Keyword(s):  
Wind Velocity ◽  
Stellar Wind ◽  
Short Wavelength ◽  
Wavelength Region ◽  
Absorption Lines ◽  
High Dispersion ◽  
High Excitation ◽  
Short Wavelength Region

The high excitation planetaries NGC 1535 and 4361 were observed with IUE satellite in the short wavelength region at high dispersion. In NGC 1535 we found P Cygni profiles of NV 1238, 1242 and OV 1371 lines with a terminal wind velocity of about 2000 km/sec. In NGC 4361 these lines are narrow absorption lines (width 0.5 Å), probably of photospheric origin.

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