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Träfflista för sökning "WFRF:(Kaminska D) ;pers:(Kaminska M)"

Sökning: WFRF:(Kaminska D) > Kaminska M

  • Resultat 1-10 av 28
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1.
  • Ehlerding, A., et al. (författare)
  • The dissociative recombination of fluorocarbon ions III : CF2+ and CF3
  • 2006
  • Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 39:4, s. 805-812
  • Tidskriftsartikel (refereegranskat)abstract
    • Cross sections and branching ratios are presented for the dissociative recombination of the CF2+ and C-3(+) ions with electrons. It is found that the channel producing CF + F is dominant for the reaction with CF2+ and the production of CF2 + F is dominant for the reaction with CF3+. The cross sections for these two ions are very similar.
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2.
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3.
  • Geppert, W. D., et al. (författare)
  • Dissociative recombination of CD3OD2
  • 2005
  • Ingår i: Proceedings of the International Astronomical Union. - 1743-9213 .- 1743-9221. ; 1, s. 117-124
  • Tidskriftsartikel (refereegranskat)abstract
    • The branching ratios of the different reaction pathways and the overall rate of the dissociative recombination of CD3OD2 + were measured at the CRYRING storage ring located at the Manne Siegbahn Laboratory in Stockholm, Sweden. A preliminary analysis of the data yielded that formation of methanol accounts for only 6±2% of the total reaction rate. Largely, dissociative recombination of CD3OD 2 + involves fragmentation of the C-O bond, the major process being the three-body break-up forming CD3, OD and D (branching ratio 0.59). A non-negligible formation of interstellar methanol by the previously proposed mechanism is therefore very unlikely.
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4.
  • Geppert, W.D., et al. (författare)
  • Dissociative recombination of protonated methanol
  • 2006
  • Ingår i: Faraday discussions. - Cambridge : Royal Society of Chemistry (RSC). - 1359-6640 .- 1364-5498. ; 133, s. 177-190
  • Tidskriftsartikel (refereegranskat)abstract
    • The branching ratios of the different reaction pathways and the overall rate coefficients of the dissociative recombination reactions of CH3OH2+ and CD3OD2+ have been measured at the CRYRING storage ring located in Stockholm, Sweden. Analysis of the data yielded the result that formation of methanol or deuterated methanol accounted for only 3 and 6% of the total rate in CH3OH2+ and CD3OD2+, respectively. Dissociative recombination of both isotopomeres mainly involves fragmentation of the C - O bond, the major process being the three-body break-up forming CH3, OH and H (CD3, OD and D). The overall cross sections are best fitted by sigma = 1.2 +/- 0.1 x 10(-15) E-1.15 +/- 0.02 cm(2) and sigma = 9.6 +/- 0.9 x 10(-16) E-1.20 +/- 0.02 cm(2) for CH3OH2+ and CD3OD2+, respectively. From these values thermal reaction rate coefficients of k(T) = 8.9 +/- 0.9 x 10(-7) (T/300) (- 0.59 +/- 0.02) cm(3) s(-1) (CH3OH2+) and k( T) = 9.1 +/- 0.9 x 10(-7) (T/ 300) (- 0.63 +/- 0.02) cm(3) s(-1)(CD3OD2+) can be calculated. A non-negligible formation of interstellar methanol by the previously proposed mechanism via radiative association of CH3+ and H2O and subsequent dissociative recombination of the resulting CH3OH2+ ion to yield methanol and hydrogen atoms is therefore very unlikely.
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5.
  • Geppert, W. D., et al. (författare)
  • Formation of biomolecule precursors in space
  • 2007
  • Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 88:1, s. 012068-
  • Tidskriftsartikel (refereegranskat)abstract
    • Alcohols and nitriles not only play an important role as templates for synthesis of larger molecules in the interstellar medium and planetary atmospheres, but they can also be regarded as precursors for biomolecules. Alcohols can form carbohydrates through reaction with HCO and nitriles can be hydrolysed to amino acids in aqueous solutions, which is the final step of the well-known Strecker synthesis. Therefore the question of the pathways of formation of alcohols and nitriles and the efficiency and the product distribution of their subsequent degradation reactions in the above-mentioned astrophysical environments is of great interest. In both processes dissociative recombination reactions of protonated nitriles and alcohols may play a major role and are included in models of interstellar clouds and planetary atmospheres. However, the reaction rate coefficients and product branching ratios for the majority of these processes are so far still unknown, which adversely affects the quality of predictions of model calculations. In this Contribution, we therefore present branching ratios and rate constants of the dissociative recombination of protonated methanol (CH3OH 2), as well as protonated acetonitrile (CH3CNH +), acrylonitrile (C2H3CNH+) and cyanoacetylene (HC3NH+). The impact of the obtained new data on model calculations of abundances of important interstellar molecules in dark clouds is discussed.
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6.
  • Montaigne, Helen, et al. (författare)
  • Dissociative recombination of the thioformyl (HCS+) and carbonyl sulfide (OCS+) cations
  • 2005
  • Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 631:1, s. 653-659
  • Tidskriftsartikel (refereegranskat)abstract
    • Branching ratios and absolute cross sections have been measured for the dissociative recombination of HCS+ and OCS+ at the CRYRING ion storage ring. In the case of OCS+, the channel leading to CO + S ( 83%) dominates, whereas the other exoergic pathways leading to CS + O (14%) and C + SO (3%) are of lesser importance. In the case of HCS+, fracture of the C - S bond is predominant (81%), with the production of H + CS accounting for the remainder (19%). The cross section of the reaction could be fitted by the expressions sigma = 1.41 x 10(-15)E(eV)(-1.11) and 4.47 x 10(-16)E(eV) (-1.14) cm(2) for HCS+ and OCS+, respectively. The derived energy dependences of the thermal reaction rate coefficients can be fitted by k(T) 9.7 x 10(-7)(T/300)(-0.57) and 3.5 x 10(-7)(T/300)(-0.62) cm(3) s(-1) for HCS+ and OCS+, respectively. We use these data to perform model calculations on the HCS+/CS abundance ratio in dark clouds and find that the models using the UMIST and Ohio State University databases have even more difficulty in accounting for the large observed ratio.
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7.
  • Novotny, O, et al. (författare)
  • The dissociative recombination of fluorocarbon ions : II. CF
  • 2005
  • Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 38:10, s. 1471-1482
  • Tidskriftsartikel (refereegranskat)abstract
    • The dissociative recombination and excitation of CF+ have been measured at the ASTRID and CRYRING storage rings. Though examination of the available potential energy curves would suggest that the recombination rate would be large for this ion, in fact a rate constant of 5.2 +/- 1.0 x 10(-8) (T-e/300)(-0.8) cm(3) s(-1) was found. The recombination cross section at low energies falls off to a minimum at 0.5 eV centre-of-mass collision energy but exhibits resonances at energies above this. The dissociative excitation cross section leading to C+ + F was also measured and this displays an onset beginning at about 7 eV.
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8.
  • Viggiano, A. A., et al. (författare)
  • Rate constants and branching ratios for the dissociative recombination of CO2
  • 2005
  • Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 122:22, s. 226101-
  • Tidskriftsartikel (refereegranskat)abstract
    • The calculation of rate constants and branching ratios was carried out to study the dissociative recombination of CO2+. The recombination of CO2+ is significant in the atmospheres of Venus and Mars. Rate constants and cross sections were studied by ramping the electron beam around a center-of-mass energy of 0 eV. The results of the study confirms that all the recombination of CO2+ results in a simple bondbreaking to form CO plus O. The rate constants show good agreement with measurements at 300 K and the electron energy dependence is identical to storage ring results.
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9.
  • Vigren, E., et al. (författare)
  • Collision-induced dissociation of ∼2-MeV O+3 and N+3 ions
  • 2013
  • Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 87:5
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a study into the collision-induced dissociation (possibly including electron stripping) of O-3(+) and N-3(+) with rest gas molecules (predominantly H-2) in the heavy-ion storage ring CRYRING. The projectile ions had kinetic energies of 1.96 MeV (O-3(+)) and 2.25 MeV (N-3(+)) and from the experimental data we could derive the relative importance of the channels that produce at least one neutral product fragment. The dominant type of fragmentation for both ions involves the production of a single neutral fragment, namely an individual atom. We also find pronounced dissimilarities when comparing the O-3(+) and N-3(+) results, which we link to the stronger chemical bonds in the nitrogen system.
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10.
  • Vigren, Erik, et al. (författare)
  • Dissociative recombination of nitrile ions with implications for Titan's upper atmosphere
  • 2012
  • Ingår i: Planetary and Space Science. - : Elsevier BV. - 0032-0633 .- 1873-5088. ; 60:1, s. 102-106
  • Tidskriftsartikel (refereegranskat)abstract
    • Nitrile ions are abundant in Titan's upper atmosphere and are expected to be lost mainly via dissociative recombination with free electrons. We review in this paper a series of experimental results on the dissociative recombination reactions of nitrile ions known/expected to be present in Titan's upper atmosphere. The experiments were all performed at the heavy ion storage ring CRYRING in Stockholm, Sweden, and the results presented here include information on rate coefficients at electron temperatures relevant for Titan's upper atmosphere as well as information on the product branching fractions of the reactions. We discuss implications of the results for Titan's atmosphere. As an example the presented results support a statement by Krasnopolsky (2009) that nitriles do not degrade to yield N-2 again in Titan's atmosphere, indicating that condensation and polymerization with precipitation to the surface are their ultimate fate.
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