Semiempirical formulae for dipole excitation cross sections and rate coefficients in atoms and ions

1991 ◽  
Vol 43 (3) ◽  
pp. 266-269 ◽  
Author(s):  
V P Shevelko
Keyword(s):  
Cross Sections ◽  
Rate Coefficients ◽  
Dipole Excitation ◽  
Excitation Cross Sections

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.

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 Diffusion, Attachment and Attachment Cooling of Thermal Electrons in Oxygen and Oxygen Mixtures

1983 ◽  
Vol 36 (6) ◽  
pp. 831 ◽  
Author(s):  
R Hegerberg ◽  
RW Crompton
Keyword(s):  
Diffusion Coefficient ◽  
Cross Sections ◽  
Rate Coefficient ◽  
Resonance Energy ◽  
Sampling Technique ◽  
Rate Coefficients ◽  
Rotational Excitation ◽  
Attachment Rate ◽  
Excitation Cross Sections ◽  
Three Body

The Cavalieri electron density sampling technique has been used to measure the diffusion and attachment rate coefficients for thermal electrons in O2, and in O2–N2 and O2–C02 mixtures. The observed pressure dependence of the three-body attachment rate coefficient va/N2 is shown to be caused by the selective removal of electrons from the distribution at the attachment resonance energy, and the magnitude of this effect (so-called 'attachment cooling') is shown to be a measure of the magnitude of the rotational excitation cross sections in O2 and N2. Three-body rate coefficients for the formation of O2 involving O2, N2 and CO¯2 as third bodies have been found to be 2.2,011 and 3.5 X 10¯30 cm6 S¯l respectively. The value of the diffusion coefficient ND for thermal electrons in O2 is found to be (37 � 3) x 1021 cm¯1s¯1.

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.

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