Cross Sections and Excitation Rate Coefficients for the 2s22p52P3/2-2s22p52P1/2 Transition in Fluorine-Like Ions by p,d,t and α Impact

1994 ◽  
Vol 58 (2) ◽  
pp. 227-244 ◽  
Author(s):  
V.J. Foster ◽  
F.P. Keenan ◽  
R.H.G. Reid
Keyword(s):  
Cross Sections ◽  
Rate Coefficients ◽  
Excitation Rate

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.

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.

scholarly journals Recent Advances in Atomic Calculations and Experiments of Interest in the Study of Planetary Nebulae

1983 ◽  
Vol 103 ◽  
pp. 143-172 ◽  
Author(s):  
C. Mendoza
Keyword(s):  
Cross Sections ◽  
Transition Probabilities ◽  
Planetary Nebulae ◽  
Electron Excitation ◽  
Rate Coefficients ◽  
Excitation Rate ◽  
Recent Advances

Recent advances in the calculation and measurement of transition probabilities, electron excitation rate coefficients and photoionization cross sections relevant to the study of planetary nebulae are discussed. A compilation of these parameters is also presented.

Rotational de-excitations of C3H+ (1Σ+) by collision with He: new ab initio potential energy surface and scattering calculations

2020 ◽  
Vol 494 (4) ◽  
pp. 5675-5681 ◽  
Author(s):  
Sanchit Chhabra ◽  
T J Dhilip Kumar
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Ab Initio ◽  
Cross Sections ◽  
Energy Surface ◽  
Molecular Ions ◽  
Basis Set ◽  
Rate Coefficients ◽  
Close Coupling ◽  
Collisional Rate Coefficients

ABSTRACT Molecular ions play an important role in the astrochemistry of interstellar and circumstellar media. C3H+ has been identified in the interstellar medium recently. A new potential energy surface of the C3H+–He van der Waals complex is computed using the ab initio explicitly correlated coupled cluster with the single, double and perturbative triple excitation [CCSD(T)-F12] method and the augmented correlation consistent polarized valence triple zeta (aug-cc-pVTZ) basis set. The potential presents a well of 174.6 cm−1 in linear geometry towards the H end. Calculations of pure rotational excitation cross-sections of C3H+ by He are carried out using the exact quantum mechanical close-coupling approach. Cross-sections for transitions among the rotational levels of C3H+ are computed for energies up to 600 cm−1. The cross-sections are used to obtain the collisional rate coefficients for temperatures T ≤ 100 K. Along with laboratory experiments, the results obtained in this work may be very useful for astrophysical applications to understand hydrocarbon chemistry.

Inelastic scattering of interstellar silyl cyanide (SiH3CN) by helium atoms : cross-sections and rate coefficients for A- and E-SiH3CN

2021 ◽  
Vol 507 (4) ◽  
pp. 5264-5271
Author(s):  
Manel Naouai ◽  
Abdelhak Jrad ◽  
Ayda Badri ◽  
Faouzi Najar
Keyword(s):  
Inelastic Scattering ◽  
Total Energy ◽  
Cross Sections ◽  
Three Dimensional ◽  
Basis Set ◽  
Rate Coefficients ◽  
Close Coupling ◽  
Explicitly Correlated ◽  
Correlation Consistent ◽  
Triple Excitation

ABSTRACT Rotational inelastic scattering of silyl cyanide (SiH3CN) molecule with helium (He) atoms is investigated. Three-dimensional potential energy surface (3D-PES) for the SiH3CN–He interacting system is carried out. The ab initio 3D-PES is computed using explicitly correlated coupled cluster approach with single, double, and perturbative triple excitation CCSD(T)-F12a connected to augmented-correlation consistent-polarized valence triple zeta Gaussian basis set. A global minimum at (R = 6.35 bohr; θ = 90○; ϕ = 60○) with a well depth of 52.99 cm−1 is pointed out. Inelastic rotational cross-sections are emphasized for the 22 first rotational levels for total energy up to 500 cm−1 via close coupling (CC) approach in the case of A-SiH3CN and for the 24 first rotational levels for total energy up to 100 cm−1 via CC and from 100 to 500 cm−1 via coupled states (CS) in the case of E-SiH3CN. Rate coefficients are derived for temperature until 80 K for both A- and E-SiH3CN–He systems. Propensity rules are obtained for |ΔJ| = 2 processes with broken parity for A-SiH3CN and for |ΔJ| = 2 processes with |ΔK| = 0 and unbroken parity for E-SiH3CN.

scholarly journals BASECOL2020 New Technical Design

Atoms ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 69 ◽  
Author(s):  
Yaye-Awa Ba ◽  
Marie-Lise Dubernet ◽  
Nicolas Moreau ◽  
Carlo Maria Zwölf
Keyword(s):  
Interstellar Medium ◽  
Data Center ◽  
Molecular Data ◽  
International Standards ◽  
Rate Coefficients ◽  
Collisional Excitation ◽  
Excitation Rate ◽  
Single Location ◽  
Molecular Databases ◽  
Key Features

The BASECOL database has been created and scientifically enriched since 2004. It contains collisional excitation rate coefficients of molecules for application to the interstellar medium and to cometary atmospheres. Recently, major technical updates have been performed in order to be compliant with international standards for management of data and in order to provide a more friendly environment to query and to present the data. The current paper aims at presenting the key features of the technical updates and to underline the compatibility of BASECOL database with the Virtual Atomic and Molecular Data Center. This latter aims to interconnect atomic and molecular databases, thus providing a single location where users can access atomic and molecular data.

scholarly journals Electron-impact double ionization of the carbon atom

2018 ◽  
Vol 620 ◽  
pp. A188 ◽  
Author(s):  
Valdas Jonauskas
Keyword(s):  
Carbon Atom ◽  
Electron Impact ◽  
Cross Sections ◽  
Double Ionization ◽  
Impact Excitation ◽  
Rate Coefficients ◽  
Electron Impact Excitation ◽  
Ionization Cross ◽  
Ionization Cross Sections ◽  
Good Agreement

Electron-impact single- and double-ionization cross sections and Maxwellian rate coefficients are presented for the carbon atom. Scaling factors are introduced for the electron-impact excitation and ionization cross sections obtained in the distorted wave (DW) approximation. It is shown that the scaled DW cross sections provide good agreement with measurements for the single ionization of the C atom and C1+ ion. The direct double-ionization (DDI) process is studied using a multi-step approach. Ionization–ionization, excitation–ionization–ionization, and ionization–excitation–ionization branches are analyzed. It is demonstrated that the three-step processes contribute ≼40% of the total DDI cross sections for the case where one of the electrons takes all of the excess energy after the first ionization process.

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