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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 189 (1961), S. 652-653 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Suppose that the ions are protons and suppose also that the temperature is such that the mean thermal energy is much less than the first excitation energy of hydrogen. Radiative recombination is slow but highly excited hydrogen atoms are rapidly formed through electron-electron collisions: These ...
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 58 (1994), S. 23-27 
    ISSN: 1432-0649
    Keywords: 42.55.V
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have investigated the Ne-like yttrium collisionally pumped laser using a detailed time dependent collisional radiative model within a fluid code (EHYBRID), and post-processors to investigate the effects of refraction and saturation. We conclude that, in addition to that on the twoJ = 2 → 1 lines, gain is generated on theJ = 0 → 1 transition and that this line very closely overlaps theJ = 2 → 1 transition at 155 Å. A 50% reduction in the calculated monopole excitation rate which pumps theJ = 0 → 1 line (a notoriously uncertain quantity) is required to obtain satisfactory agreement with experiment — the same modification as was required for the germanium laser.
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  • 3
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract RecentR-matrix calculations of electron impact excitation rates in Ov are used to derive the emission line intensity ratios (in energy units) $$\begin{gathered} R_1 = I(2s2p^{ 3} P - 2p^{2 3} P)/I(2s^{2 1} S_0 - 2s2p^{ 1} P_1 ) = I(761.1\mathop A\limits^ \circ )/I(629.7\mathop A\limits^ \circ ), \hfill \\ R_2 = I(2s^{2 1} S_0 - 2s2p^{ 3} P_1 )/I(2s^{2 1} S_0 - 2s2p^{ 1} P_1 ) = I(1218.4\mathop A\limits^ \circ )/I(629.7\mathop A\limits^ \circ ), \hfill \\ \end{gathered} $$ and $$R_3 = I(2s2p^{ 1} P_1 - 2p^{2 1} S_0 )/I(2s^{2 1} S_0 - 2s2p^{ 1} P_1 ) = I(774.5\mathop A\limits^ \circ )/I(629.7\mathop A\limits^ \circ )$$ as a function of electron temperature (T e) and density (N e). These results are presented as plots ofR 1 vsR 2, andR 1 vsR 3, which should allowboth N e andT e to be deduced for the Ov line emitting region of a plasma. Electron densities derived from the (R 1,R 2) and (R 1,R 3) diagrams in conjunction with observational data for several solar features obtained with the Harvard S-055 spectrometer on boardSkylab are found to be compatible, and in good agreement with values ofN e estimated from line ratios in species formed at similar electron temperatures to Ov. In addition, values ofT e determined from (R 1,R 2) and (R 1,R 3) are generally close to that expected theoretically. These results provide experimental support for the accuracy of the diagnostic calculations presented in this paper, and hence the atomic data used in their derivation.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 105 (1986), S. 313-322 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Theoretical populations of the 2s3l levels of Ne vii are presented for electron temperatures from 2.5 × 105 K to 4 × 106 K and electron densities from 108 cm−3 to 1012 cm−3. These, in conjunction with intensities of previously observed solar Ne vii lines and wavelengths and intensities observed in the laboratory, are used to identify further Ne vii lines in the solar spectrum. The dependence on temperature of intensity ratios such as I(2s2p 1 P − 2s3d 1 D)/I(2s2p 3 P − 2s3d 3 D) is demonstrated and the advantages of the small wavelength separation of such lines for solar electron temperature diagnostics are discussed.
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  • 5
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The EUV observations from the SMM satellite of two sunspots are presented here. These observations show the sunspots (a) to be regions of lower intensity than the surrounding plage, contrary to that found by previous authors, and (b) to have line intensities which vary little over a period of several hours. An upper limit to mass flows of 2km s-1 is derived, indicating a relatively simple energy balance for the chromosphere-corona transition zone with thermal conduction being balanced by radiative losses. Electron densities derived from Niv to Civ line ratios imply electron pressures (log N eTe) of 15.0 to 15.3.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 92 (1984), S. 75-79 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract New electron excitation rates for O vii calculated by Tayal and Kingston using the R-matrix method are used to determine theoretical emission line strengths. Values of the electron density sensitive ratio R (forbidden line to intercombination line) are found to be very similar to those deduced by other authors. However the temperature sensitive ratios G (intercombination plus forbidden lines to resonance line) are approximately 20% lower than the best previous estimates. The observed value of G for solar active regions (G = 1.0 ± 0.1) predicts an electron temperature in the range 1.1 × 106 K 〈 T e 〈 1.8 × 106 K, which overlaps that of maximum O vii emissivity, T M = 1.8 × 106 K. In addition, the theoretical G versus T e curve is in excellent agreement with that observed for a Tokamak plasma.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 103 (1986), S. 225-230 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Recent R-matrix calculations of electron excitation rates for Mg vii and Si ix are used to determine the theoretical density sensitive emission line ratios R 1= I(2s2p 3 1 D 0 - 2s 2 2p 2 1 D e )/I(2s2p 3 3 S 0 - 2s 2 2p 2 3 P 2 e ) and R 2= I(2s2p 3 1 P 0 - 2s 2 2p 2 1 D e )/I(2s2p 3 3 S 0 - 2s 2 2p 2 3 P 2 e ). These are found to be quite similar to the earlier results of Mason and Bhatia. Electron densities derived using observed R 1 and R 2 ratios from Skylab NRL XUV spectra of solar flares and active regions are in good agreement, and compare favourably with those deduced from ions formed at similar electron temperatures to Mg vii and Si ix.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 89 (1983), S. 243-251 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract New O v rate coefficients are used to calculate the ratio of the intensity of the 760 Å multiplet to that of the 630 Å line. Results are given for a range of electron densities and temperatures. The theoretical ratios are compared with observed line ratios for different solar regions.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 94 (1984), S. 91-98 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract New theoretical emission line ratios for the Be-sequence ions Mgix and Sixi are presented. A comparison with observational data for two solar flares and an active region loop obtained with the Harvard EUV spectrometer and NRL XUV spectroheliograph aboard Skylab reveals that these plasmas are in ionization equilibrium at coronal temperatures. Unfortunately most of the density diagnostics are not particularly useful under solar plasma conditions, as they vary only slightly over the electron density range 108–1013cm−3. However the Sixi ratioI(3 P e 2 -3 P o 2)/I(3 P o 1 –1 S e 0) is density sensitive in the range 108 to 1010cm−3, which is representative of electron densities found in solar active regions or small flares.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 94 (1984), S. 85-89 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract R-matrix calculations of the 11S - 23S and 11S - 23P electron excitation rates in He - like Cv, Ovii, and Mgxi by Kingston and Tayal are used to interpolate results for Neix. Adoption of these in emission line strength calculations leads to values for the density-sensitiveR ratio very similar to those of Pradhanet al. and Wolfsonet al., although the temperature-sensitiveG ratios are approximately 10 to 20 % lower than those deduced by these authors. However the present theoretical value ofG at the temperature of maximum Neix emission,G(T m) = 0.82, is in excellent agreement with those observed by the SMM and P78-1 satellites for the 1980, November5 flare (G = 0.83 ± 0.01) and nonflaring active regions (G = 0.80 ± 0.05), respectively.
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