scholarly journals Photolysis of diatomic molecules as a source of atoms in planetary exospheres

2020 ◽  
Vol 633 ◽  
pp. A39 ◽  
Author(s):  
R. R. Valiev ◽  
A. A. Berezhnoy ◽  
I. S. Gritsenko ◽  
B. S. Merzlikin ◽  
V. N. Cherepanov ◽  
...  

We calculated the cross sections of photolysis of OH, LiO, NaO, KO, HCl, LiCl, NaCl, KCl, HF, LiF, NaF, and KF molecules using quantum chemistry methods. The maximal values for photolysis cross sections of alkali metal monoxides are on the order of 10−18 cm2. The lifetimes of photolysis for quiet Sun at 1 astronomical unit are estimated as 2.0 × 105, 28, 5, 14, 2.1 × 105, 225, 42, 52, 2 × 106, 35 400, 486, and 30 400 s for OH, LiO, NaO, KO, HCl, LiCl, NaCl, KCl, HF, LiF, NaF, and KF, respectively. We performed a comparison between values of photolysis lifetimes obtained in this work and in previous studies. Based on such a comparison, our estimations of photolysis lifetimes of OH, HCl, and HF have an accuracy of about a factor of 2. We determined typical kinetic energies of main peaks of photolysis-generated metal atoms. Impact-produced LiO, NaO, KO, NaCl, and KCl molecules are destroyed in the lunar and Hermean exospheres almost completely during the first ballistic flight, while other considered molecules are more stable against destruction by photolysis.

Atoms ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 2
Author(s):  
Annarita Laricchiuta ◽  
Roberto Celiberto ◽  
Gianpiero Colonna

The Binary-Encounter Bethe approach was applied to the estimation of total ionization induced by electron impact in metastable states of diatomic molecules. The cross sections recently obtained for N2 and CO are reviewed and the new results for H2 are presented, discussing their reliability through the comparison with other theoretical methods.


1965 ◽  
Vol 137 (4A) ◽  
pp. A1058-A1061 ◽  
Author(s):  
Robert H. McFarland ◽  
John D. Kinney

2005 ◽  
Vol 31 (5) ◽  
pp. 397-399
Author(s):  
M. A. Kulov ◽  
N. O. Vasetskaya ◽  
V. K. Ivanov

The intensity of fluorescence of thallium has been measured in hydrogen-oxygen flames diluted with each of the gases, argon, helium, nitrogen and carbon dioxide and the measurements used to obtain the following values for the quenching cross section (Å 2 ) for the 7 s 2 S ½ state of thallium σ 2 H 2 = 0.03, σ 2 O 2 = 13.2 ± 1.5, σ 2 N 2 = 6.4 ± 0.2, σ 2 H 2 O = 1.75 ± 0.2, σ 2 CO = 13.6 ± 0.8, σ 2 CO 2 = 32.5 ± 1.5, σ 2 Ar ≤ 0.1, σ 2 He ≤ 0.12. These values for the cross sections have been used to re-calculate the rate constants of the reactions, Tl + H + X → H X + Tl*, where X = H, OH, Cl or Br, from the data obtained by Phillips & Sugden (1961). The re-calculated values are lower than the original ones by a factor of 2.2.


1989 ◽  
Vol 39 (3) ◽  
pp. 1526-1529 ◽  
Author(s):  
R. W. Berends ◽  
W. Kedzierski ◽  
W. E. Baylis ◽  
L. Krause

Absorption measurements are reported for the metal vapours potassium, rubidium and caesium and existing data for lithium and sodium are reviewed. The separation of atomic and molecular absorption is discussed and the data presented as absolute cross-section curves as a function of wavelength. The shapes of the atomic photoionization continua and their absolute values are discussed in relation to existing theoretical cross-sections data. Best experimental values of the cross-sections at the series limits are found to be : Li = 1.9 ± 0.2 Mb, Na = 0.125 ± 0.01 Mb, K = 0.007 ± 0.002 Mb, Rb = 0.10 ± 0.015 Mb and Cs = 0.20 ± 0.03 Mb. The curves for potassium, rubidium and caesium have non-zero minima and that for sodium has a minimum which is near zero. Experimental minimum values of 4 ± 2 x 10 -3 Mb, 8 ± 3 x 10 -3 Mb and 6 ± 1 x 10 -2 Mb for potassium, rubidium and caesium respectively are obtained.


A method of determining the cross sections for the quenching of excited metal atoms by molecules and atoms which may be present in flames is described. The method has been applied to the quenching of sodium atoms in the 3 p 2 P state and the following results (in Å 2 ) for the square of the distance between the centres of colliding species, σ 2 , obtained: σ 2 H 2 = 2.87 ± 0.1; σ 2 N 2 = 6.95 ± 0.15; σ 2 CO = 11.9 ± 0.4; σ 2 CO 2 = 17.0 ± 0.4; σ 2 H 2 O = 0.5 ± 0.3; σ 2 O 2 = 12.3 ± 0.5; σ 2 Ar < 0.1; σ 2 He < 0.1. These cross sections have been measured at temperatures in the range 1400°K to about 1800°K and found to be independent of the temperature. The values for the cross sections are derived from measurements of the fluorescence of sodium in hydrogen-oxygen flame diluted with various other gases. This method is believed to be free of uncertainties due to self-absorption, compound formation, line broadening effects and uncertain velocity distributions. Where values for cross sections have been obtained by other workers they are compared with these results and possible reasons for the discrepancies are discussed.


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