The Relative Intensities of Lines From Bel-Like Ions in the Solar Spectrum

1971 ◽  
Vol 2 ◽  
pp. 519-526 ◽  
Author(s):  
Carole Jordan
Keyword(s):  
Cross Sections ◽  
Solar Spectrum ◽  
Rate Coefficients ◽  
Private Communication ◽  
Intensity Data ◽  
Excitation Rate ◽  
Excitation Cross Sections ◽  
Intensity Ratios ◽  
Intercombination Line

The permitted transitions 2s21S-2s2p1P and 2s2p3P-2p23P in the Bel-like ions CIII, NIV and OV have been observed for some years in the solar spectrum (Hall et al., 1963). Recently, intensity data have also been obtained for the intercombination line 2s21S-2s2p3P1 in these ions (Burton et al., 1970). A large number of excitation rate coefficients are needed before the intensity ratios of these transitions can be computed and compared with those observed. These excitation cross-sections are now becoming available (Osterbrock, 1970; Eissner, private communication), and the present paper gives the results of an analysis of the intensity data. Figure 1 shows a partial term scheme for the Bei-like ions and the observed transitions.

scholarly journals Excitations of the nS States of Atomic Hydrogen by Electron Impact, Excitation Rate Coefficients, and Phase Shifts: Comparison with Positron Impact Excitation

Atoms ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 5
Author(s):  
Anand K. Bhatia
Keyword(s):  
Electron Impact ◽  
Cross Sections ◽  
Atomic Hydrogen ◽  
Phase Shifts ◽  
Impact Excitation ◽  
Rate Coefficients ◽  
Orbital Method ◽  
Positron Impact ◽  
Excitation Rate ◽  
Excitation Cross Sections

The excitation cross-sections of the nS states of atomic hydrogen, n = 2 to 6, by electron impact on the ground state of atomic hydrogen were calculated using the variational polarized-orbital method at various incident electron energies in the range 10 to 122 eV. Converged excitation cross-sections were obtained using sixteen partial waves (L = 0 to 15). Excitation cross-sections to 2S state, calculated earlier, were calculated at higher energies than before. Results obtained using the hybrid theory (variational polarized orbital method) are compared to those obtained using other approaches such as the Born–Oppenheimer, close-coupling, R-matrix, and complex-exterior scaling methods using only the spherical symmetric wave functions. Phase shifts and elastic cross-sections are given at various energies and angular momenta. Excitation rate coefficients were calculated at various electron temperatures, which are required for plasma diagnostics in solar and astrophysics to infer plasma parameters. Excitation cross-sections are compared with those obtained by positron impact excitation.

Collision excitation of sodium cyanide molecule by helium at low temperature

2019 ◽  
Vol 489 (3) ◽  
pp. 4322-4328
Author(s):  
C Gharbi ◽  
Y Ajili ◽  
D Ben Abdallah ◽  
M Mogren Al Mogren ◽  
M Hochlaf
Keyword(s):  
Electronic Structure ◽  
Cross Sections ◽  
Energy Surface ◽  
Three Dimensional ◽  
Sodium Cyanide ◽  
Rate Coefficients ◽  
Quantum Scattering ◽  
Stable Form ◽  
Excitation Cross Sections ◽  
Order Of Magnitude

ABSTRACT Cyanides/isocyanides are the most common metal-containing molecules in interstellar medium. In this work, quantum scattering calculations were carried out to determine the rotational (de-)excitation cross-sections of the most stable form of the sodium cyanide molecule, t-NaCN, in collision with the helium atom. Rate coefficients for the first 43 rotational levels (up to ${j_{{K_a}{K_c}}}$ = 63,3) of NaCN were determined for kinetic temperatures ranging from 1 to 30 K. Prior to that, we constructed a new three-dimensional potential energy surface (3D-PES) for the t-NaCN–He interacting system. These electronic structure computations are done at the CCSD(T)-F12/aug-cc-pVTZ level of theory. Computations show the dominance of Δj = ΔKc = −1 transitions, which is related to the dissymmetric shape of the t-NaCN–He 3D-PES. The NaCN–He rate coefficients are of the same order of magnitude (∼10−11 cm3.s−1) as those of other metal CN-containing molecules such as MgCN and AlCN in collision with He. This work is a contribution for understanding and modelling the abundances and chemistry of nitriles in astrophysical media.

scholarly journals On the Interpretation of the Relative Intensities of the Solar XUV Lines of Lithium-Like Ions

1972 ◽  
Vol 14 ◽  
pp. 738-739
Author(s):  
D. R. Flower
Keyword(s):  
Cross Sections ◽  
Electron Excitation ◽  
Energy Separation ◽  
Temperature Structure ◽  
Isoelectronic Sequence ◽  
Ionization Equilibrium ◽  
Excitation Cross Sections ◽  
Powerful Means ◽  
Intensity Ratios ◽  
Equilibrium Calculations

The relative intensities of the 2s–2p and 2l–3l′ (l=0, l′= 1; l= 1, l′ = 0, 2) solar XUV lines of ions in the lithium isoelectronic sequence are sensitive to electron temperature because of the large energy separation of the 2p and 3/’ levels. Recent observations of these lines for three members of the sequence, O+5, Ne+7 and Mg+9 (Heroux and Cohen, 1971), consequently provide a potentially powerful means of studying the temperature structure of the upper chromosphere-corona transition region. These observations have been examined in the light of recent calculations of the electron excitation cross-sections for the relevant transitions (Flower, 1971). It is found that the observed intensity ratios are systematically greater than values calculated assuming that all the lines of a given ion are produced at essentially the same temperature, namely, the temperature for which the ionization equilibrium calculations of Jordan (1969) predict that emission in the lines is most highly favoured. Part of the discrepancy is removed if this assumption is dropped and the emission in each line is calculated separately before taking the ratio. These two calculations do not yield the same result because there is a high temperature tail in the ionization curve of the lithium-like ions which results in the transitions of higher excitation energy, the 2l–3l′ transitions, being enhanced relative to the 2s–2p transition. The unsatisfactory agreement between theory and observation could have important implications for current theories of the ionization equilibrium, but, before definite conclusions can be reached, further observations of the same type need to be made and remaining uncertainties in the cross-sections to be resolved.

scholarly journals Rotational relaxation of HCO+ and DCO+ by collision with H2

2020 ◽  
Vol 497 (4) ◽  
pp. 4276-4281 ◽  
Author(s):  
Otoniel Denis-Alpizar ◽  
Thierry Stoecklin ◽  
Anne Dutrey ◽  
Stéphane Guilloteau
Keyword(s):  
Cross Sections ◽  
Rate Coefficients ◽  
Local Thermal Equilibrium ◽  
Rotational Relaxation ◽  
Close Coupling ◽  
Excitation Rate ◽  
Rotational States ◽  
Non Local ◽  
The Difference ◽  
Isotopic Effects

ABSTRACT The HCO+ and DCO+ molecules are commonly used as tracers in the interstellar medium. Therefore, accurate rotational rate coefficients of these systems with He and H2 are crucial in non-local thermal equilibrium models. We determine in this work the rotational de-excitation rate coefficients of HCO+ in collision with both para- and ortho-H2, and also analyse the isotopic effects by studying the case of DCO+. A new four-dimensional potential energy surface from ab initio calculations was developed for the HCO+–H2 system, and adapted to the DCO+–H2 case. These surfaces are then employed in close-coupling calculations to determine the rotational de-excitation cross-sections and rate coefficients for the lower rotational states of HCO+ and DCO+. The new rate coefficients for HCO+ + para-H2 were compared with the available data, and a set of rate coefficients for HCO+ + ortho-H2 is also reported. The difference between the collision rates with ortho- and para-H2 is found to be small. These calculations confirm that the use of the rate coefficients for HCO+ + para-H2 for estimating those for HCO+ + ortho-H2 as well as for DCO+ + para-H2 is a good approximation.

scholarly journals The Measurement and Interpretation of NeV 2–2 Line Intensity Ratios

1988 ◽  
Vol 102 ◽  
pp. 59-62
Author(s):  
J. Lang
Keyword(s):  
Grazing Incidence ◽  
Electron Excitation ◽  
Spectral Lines ◽  
Rate Coefficients ◽  
Experimental Result ◽  
Measured Intensity ◽  
Laser Scattering ◽  
Excitation Rate ◽  
Theta Pinch ◽  
Intensity Ratios

AbstractA theta-pinch was used to produce NeV 2–2 spectral lines. The intensities of the lines were measured using a grazing incidence spectrometer which had been intensity calibrated by the branching ratios method. The electron temperature and density of the theta-pinch discharge were found by laser scattering. The measured intensity ratios are compared to theoretical predictions based on electron excitation rate coefficients calculated using the R-matrix close coupling method. For two of the measured ratios experiment and theory agree within the experimental uncertainty, For the other two ratios the theoretical prediction is greater than the experimental result.

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