scholarly journals Investigation of Dominant States in Dielectronic Recombination Rates for Fe-Ions

2003 ◽  
Vol 58 (5-6) ◽  
pp. 346-350
Author(s):  
H. Ramadan ◽  
A. Khazbak ◽  
Ali H. Moussa
Keyword(s):  
Cross Sections ◽  
Theoretical Calculations ◽  
Dielectronic Recombination ◽  
Rate Coefficients ◽  
Recombination Rates ◽  
Semiempirical Formula ◽  
Semi Empirical ◽  
Fe Ions ◽  
Initial Capture ◽  
Good Agreement

Dielectronic recombination (DR) cross sections and rate coefficients are calculated for the isonuclear sequence FeZ+, with Z = 21, 20, 19, 18, 17, and 16, in which L-shell (2p-) excitations are involved during the initial capture. Most of the dominant transitions with Δn ≠ 0, using angular momentum average (AMA) approximation, are considered. It is found that the states 3pnd and 3dnd contribute most to the rate coefficients. In addition, the rates are found to increase with increasing number of electrons in the ion, (i. e. as Z decreases). Moreover, the rate coefficients, αDR, for the studied ions are found to peak around the same energy (kT = 30 Ry). A semi-empirical formula for the total rates α is obtained for the 2p-excitation with Δn ≠ 0 in the case of FeZ+ ions. On comparing both results, the explicit calculations and the results obtained from the semiempirical formula, good agreement is found. The available results for αDR may be considered as a database for future comparison with experimental and theoretical calculations. Comparison of our results with other results show the effect of the empirical rate formula.

scholarly journals Dielectronic recombination rate coefficients of fluorine-like nickel

2019 ◽  
Vol 627 ◽  
pp. A171 ◽  
Author(s):  
Shu-Xing Wang ◽  
Zhong-Kui Huang ◽  
Wei-Qiang Wen ◽  
Chong-Yang Chen ◽  
Stefan Schippers ◽  
...  
Keyword(s):  
Energy Range ◽  
Cross Sections ◽  
Recombination Rate ◽  
Theoretical Calculations ◽  
Dielectronic Recombination ◽  
Rate Coefficients ◽  
Experimental Result ◽  
Configuration Interaction Method ◽  
Nickel Ions ◽  
Ionized Plasmas

Electron-ion recombination rate coefficients for fluorine-like nickel ions have been measured by employing the merged-beam technique at the cooler storage ring CSRm at the Institute of Modern Physics in Lanzhou, China. The measured spectrum covers the energy range of 0–160 eV, including all the dielectronic recombination (DR) resonances associated with ΔN = 0 core excitations. The DR cross sections in this energy range were calculated by a relativistic configuration interaction method using the flexible atomic code (FAC). Radiative recombination (RR) cross sections were obtained from a modified version of the semi-classical Bethe & Salpeter (1957, Quantum Mechanics of One- and Two-Electron 56 Systems (Springer)) formula for hydrogenic ions. The comparison between the measurement and the calculation shows that the present theoretical model still needs to be improved at low collision energies. Temperature dependent plasma recombination rate coefficients were derived from the measured DR rate coefficients in the temperature range of 103–108 K and compared with the presently calculated result as well as previous available data in the literature. The experimentally derived data agree well with the theoretical calculations for temperatures where Ni19+ ions form in collisionally ionized plasmas. At lower temperatures typical for photo-ionized plasmas, discrepancies are found beyond the experimental uncertainty, which can be attributed to the disagreement between the measurement and the calculation of the low-lying DR resonances. The present experimental result benchmarks the plasma DR rate coefficients, in particular for temperatures below 105 K where the ΔN = 0 DR resonances dominate.

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.

scholarly journals Momentum Transfer Cross Section for Electrons in Mercury Vapour Derived from Drift Velocity Measurements in Mercury Vapour?Gas Mixtures

1991 ◽  
Vol 44 (6) ◽  
pp. 647 ◽  
Author(s):  
JP England ◽  
MT Elford
Keyword(s):  
Momentum Transfer ◽  
Cross Section ◽  
Drift Velocity ◽  
Cross Sections ◽  
Personal Communication ◽  
Mercury Vapour ◽  
Semi Empirical ◽  
Time Of Flight Method ◽  
Momentum Transfer Cross Section ◽  
Good Agreement

The Bradbury-Nielsen time-of-flight method has been used to measure electron drift velocities at 573 K in pure mercury vapour, a mixture of 46�80% helium-53� 20% mercury vapour and a mixture of 9�37% nitrogen-90� 63% mercury vapour. The E/N and pressure ranges used were O� 2 to 1� 5 Td and 5�4 to 15�2 kPa for pure mercury vapour, 0 �08 to 3�0 Td and 5 �40 to 26�88kPa for the mixture containing helium and 0�06 to 5�0Td and 3�33 to 16�67kPa for the mixture containing nitrogen. It is shown that the use of mixtures significantly reduces the dependence of the measured drift velocity on the pressure, due to the effect of mercury dimers, from that measured in pure mercury vapour. An iterative procedure to derive the momentum transfer cross section for electrons in mercury vapour over the range 0�04 to 4 eV with an uncertainty between �5 and 10% is described. It is concluded that previously published momentum transfer cross sections for mercury vapour derived from drift velocity data are significantly in error, due to diffusion effects and the procedure used to correct for the influence of dimers. The present cross section is in good agreement with the semi-empirical calculations of Walker (personal communication).

scholarly journals New H2O–H2O collisional rate coefficients for cometary applications

2020 ◽  
Vol 498 (4) ◽  
pp. 5489-5497 ◽  
Author(s):  
C Boursier ◽  
B Mandal ◽  
D Babikov ◽  
M L Dubernet
Keyword(s):  
Cross Sections ◽  
Potential Energy Surfaces ◽  
Rate Coefficients ◽  
Molecular Systems ◽  
Large Sets ◽  
Alternative Approach ◽  
Collisional Rate Coefficients ◽  
Energy Surfaces ◽  
Good Agreement

ABSTRACT We re-introduce a semiclassical methodology based on theories developed for the determination of broadening coefficients. We show that this simple and extremely fast methodology provides results that are in good agreement with results obtained using the more sophisticate MQCT approach. This semiclassical methodology could be an alternative approach which allows to provide large sets of collisional data for very complex molecular systems. It saves time both on the determination of potential energy surfaces and on the collisional dynamical calculations. In addition, this paper provides more complete sets of rotational de-excitation cross-sections and rate coefficients of H2O perturbed by a thermal average of water molecules. Those data can be used in the radiative transfer modelling of cometary atmospheres.

scholarly journals Rotational quenching of HD induced by collisions with H2 molecules

2019 ◽  
Vol 488 (1) ◽  
pp. 381-386
Author(s):  
Yier Wan ◽  
N Balakrishnan ◽  
B H Yang ◽  
R C Forrey ◽  
P C Stancil
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Cross Sections ◽  
Energy Surface ◽  
Rate Coefficients ◽  
Quantum Mechanical ◽  
Cooling Efficiency ◽  
Close Coupling ◽  
Rotational Transitions ◽  
Good Agreement

ABSTRACT Rate coefficients for rotational transitions in HD induced by H2 impact for rotational levels of HD j ≤ 8 and temperatures 10 K ≤ T ≤ 5000 K are reported. The quantum mechanical close-coupling (CC) method and the coupled-states (CS) decoupling approximation are used to obtain the cross-sections employing the most recent highly accurate H2–H2 potential energy surface (PES). Our results are in good agreement with previous calculations for low-lying rotational transitions The cooling efficiency of HD compared with H2 and astrophysical applications are briefly discussed.

Dissociative electron recombination of NH2CHOH+ and implications for interstellar formamide abundance

2019 ◽  
Vol 490 (1) ◽  
pp. 1325-1331 ◽  
Author(s):  
M A Ayouz ◽  
C H Yuen ◽  
N Balucani ◽  
C Ceccarelli ◽  
I F Schneider ◽  
...  
Keyword(s):  
Theoretical Calculations ◽  
Branching Ratios ◽  
Rate Coefficients ◽  
Electron Recombination ◽  
Complex Species ◽  
Star Forming ◽  
Star Forming Regions ◽  
Global Rate ◽  
Cometary Material ◽  
Good Agreement

ABSTRACT Formamide is a potentially important molecule in the context of pre-biotic chemistry, since reactions involving it can lead to precursors of genetic and metabolic molecules. Being abundant in cometary material and in star-forming regions, the formation and destruction routes of interstellar formamide have been the focus of several studies. In this work, we focus on the electron recombination of protonated formamide, an important step of its destruction routes, by performing rigorous ab initio calculations of this process. We found that our values are in good agreement with previous qualitative estimates of the global rate coefficients. On the contrary, we propose a substantial revision of the products and branching ratios. Finally, we justify and emphasize the importance of carrying out similar theoretical calculations on the largest possible number of complex species of astrochemical interest.

scholarly journals Photorecombination and Photoionization Experiments at Heavy-Ion Storage-Rings and Synchrotron-Light Sources

2005 ◽  
Vol 13 ◽  
pp. 640-643
Author(s):  
Stefan Schippers
Keyword(s):  
Cross Sections ◽  
Theoretical Calculations ◽  
Accurate Determination ◽  
Heavy Ion ◽  
Storage Rings ◽  
Rate Coefficients ◽  
Light Sources ◽  
Ion Storage ◽  
Synchrotron Light ◽  
Synchrotron Light Sources

AbstractRecent experimental work on the photorecombination and the photoionization of astrophysically relevant atomic ions employing the merged-beams technique at heavy-ion storage-rings and synchrotron-light sources, respectively, is summarized. The resulting absolute photoionization cross sections and recombination rate coefficients benchmark corresponding theoretical calculations and are needed for the accurate determination of ionization equilibria in astrophysical plasmas.

Revisiting cross sections for proton induced reactions on natural lead between 10 and 80 MeV

2021 ◽  
Vol 109 (4) ◽  
pp. 233-242
Author(s):  
Salim Gülez ◽  
Bhawna Pandey ◽  
Erik Strub
Keyword(s):  
Cross Sections ◽  
Additional Data ◽  
Historical Data ◽  
Theoretical Calculations ◽  
Historical Record ◽  
High Proton ◽  
Γ Ray ◽  
Proton Induced Reactions ◽  
Good Agreement

Abstract This work is focused on the natPb(p,xn)207Bi reaction to extend earlier works on proton induced reactions for the determination of cross sections of residual nuclides. 207Bi decay (half-life 31.55 years) was measured by γ-ray spectrometry in 42 lead foils which had been irradiated by high proton fluxes 20 years ago. Since then, all short-lived radionuclides produced during the irradiation have decayed, so the background is strongly reduced and the cross section could be measured more precisely than during the original measurements. The results are found to be in very good agreement with the historical record. Additionally, theoretical calculations with modern Monte Carlo based codes were performed to compare the calculations of various Bi, Tl and Pb reactions with the historical data and with additional data from literature. The deviations of the new data from both theoretical calculations using EMPIRE and TALYS are discussed.

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