# The influence of the temperature on electron attachment to some halocontaining molecules

TL;DR: In this article, the Pulsed Townsend technique was used to measure the thermal electron attachment rate for CH 2 ClCHClCH 2 Cl, CH 2 CLCHClCh 2 Cl and CF 2 ClCFCl 2 over the temperature range T ǫ =298-358 K. The corresponding rate coefficients at 298-K are equal to 1.7(4) −1 −10 −10, 7.9(15) −10, 3.4(5) −8 Â cm 3 Âmolec.

About: This article is published in International Journal of Mass Spectrometry.The article was published on 2010-03-15. It has received 10 citations till now.

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TL;DR: Results of R-matrix calculations for temperature-dependent rate coefficients of exothermic DEA processes with intermediate barrier toward dissociation support the idea that the exponential dependence of k(T = 300 K) on the activation energy reflects a general phenomenon associated with Franck-Condon factors for getting from the initial neutral vibrational levels to the dissociating final anion state in a direct DEA process.

Abstract: Rate coefficients k(T) for dissociative electron attachment (DEA) to molecules in many cases exhibit a more or less strong rise with increasing temperature T (the electron temperature T(e) and the molecular temperature T(G) are assumed to be in thermal equilibrium, i.e., T = T(e) = T(G)). This rise is frequently modeled by the Arrhenius equation k(T) = k(A) exp[-E(a)∕(k(B)T)], and an activation energy E(a) is deduced from fits to the experimental data k(T). This behavior reflects the presence of an energy barrier for the anion on its path to the dissociated products. In a recent paper [J. Kopyra, J. Wnorowska, M. Foryś, and I. Szamrej, Int. J. Mass Spectrom. 268, 60 (2007)] it was suggested that the size of the rate coefficients for DEA reactions at room temperature exhibits an exponential dependence on the activation energy, i.e., k(E(a); T ≈ 300 K) = k(1) exp[-E(a)∕E(0)]. More recent experimental data for molecules with high barriers [T. M. Miller, J. F. Friedman, L. C. Schaffer, and A. A. Viggiano, J. Chem. Phys. 131, 084302 (2009)] are compatible with such a correlation. We investigate the validity and the possible origin of this dependence by analyzing the results of R-matrix calculations for temperature-dependent rate coefficients of exothermic DEA processes with intermediate barrier toward dissociation. These include results for model systems with systematically varied barrier height as well as results of molecule-specific calculations for CH(3)Cl, CH(3)Br, CF(3)Cl, and CH(2)Cl(2) (activation energies above 0.2 eV) involving appropriate molecular parameters. A comparison of the experimental and theoretical results for the considered class of molecules (halogenated alkanes) supports the idea that the exponential dependence of k(T = 300 K) on the activation energy reflects a general phenomenon associated with Franck-Condon factors for getting from the initial neutral vibrational levels to the dissociating final anion state in a direct DEA process. Cases are discussed for which the proposed relation does not apply.

13 citations

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TL;DR: Electron attachment to SOF (2) and SO(2)F( 2) is nondissociative, while reaction with SOCl(2), SO(1)FCl, and SO-2)Cl(3) is dissociative and branching fraction data are reported for the Dissociative attachment channels.

Abstract: Electron attachment to SOF(2), SOCl(2), SO(2)F(2), SO(2)FCl, and SO(2)Cl(2) was studied with two flowing-afterglow Langmuir-probe apparatuses over the temperature range 300-900 K. Attachment rate coefficients at 300 K are k(a) = 2.6+/-0.8x10(-10)(SOF(2)), 1.8+/-0.5x10(-8)(SOCl(2)), 4.8+/-0.7x10(-10)(SO(2)F(2)), 2.4+/-0.7x10(-9)(SO(2)Cl(2)), and 2.0+/-0.6x10(-7) cm(3) s(-1)(SO(2)FCl). Arrhenius plots of the data imply activation energies of 56+/-22 meV(SOF(2)), 92+/-40(SO(2)F(2)), 44+/-22 meV(SOCl(2)), and 29+/-15 meV(SO(2)Cl(2)). The rate coefficients for SO(2)FCl decrease slightly with temperature, commensurate with the decrease in the capture rate coefficient. Electron attachment to SOF(2) and SO(2)F(2) is nondissociative, while reaction with SOCl(2), SO(2)FCl, and SO(2)Cl(2) is dissociative. Dissociative attachment is dominated by channels arising from S-Cl bond cleavage but also includes a minor channel forming a dihalide product ion. Branching fraction data are reported for the dissociative attachment channels.

8 citations

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TL;DR: In this article, the Pulsed Townsend technique was used to measure the thermal attachment rate of CH 3 CH 2 Br and CH 2 F 2 CH 2 2 Br molecules over the temperature range (298-378) K.

5 citations

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TL;DR: In this article, the authors report the results of the measurements of the rate coefficients for thermal attachment to several perfluoroethers namely perfluorodiglyme (C 6 F 14 O 3 ), perffluorotriglyme(C 8 F 18 O 4 ), perfluorsopolyether (CF 3 -(OCF(CF 3 )CF 2 ) n -OCF 2 ) m −OCF 3 ) and perfluoricrownether ((C 2 F 4 O) 5 ).

5 citations

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TL;DR: In this paper, the electron attachment process in the mixtures of chloroalcohols with carbon dioxide was investigated using an electron swarm technique and negative ion mass spectrometry (NIMS).

5 citations

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01 Jan 1971

TL;DR: The atomic and molecular radiation physics is what we surely mean as discussed by the authors, no matter how you got the sentences that have been read from the books, surely they will give you goodness. But, we will show you one of recommendation of the book that you need to read.

Abstract: Any books that you read, no matter how you got the sentences that have been read from the books, surely they will give you goodness. But, we will show you one of recommendation of the book that you need to read. This atomic and molecular radiation physics is what we surely mean. We will show you the reasonable reasons why you need to read this book. This book is a kind of precious book written by an experienced author.

432 citations

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TL;DR: In this paper, the authors discuss resonance and threshold phenomena in low-energy electron collisions with molecules and clusters, and the theoretical description of electron-molecule collisions generally requires an adequate description of electronic, vibrational and rotational degrees of freedom.

Abstract: Publisher Summary This chapter discusses resonance and threshold phenomena in low-energy electron collisions with molecules and clusters. Low-energy collisions of electrons with atoms and molecules are among the most important elementary processes in gaseous environments such as discharges, arcs, gas lasers, gaseous dielectrics and the earth's atmosphere. The dynamics behavior of low-energy electron-molecule collisions is discussed. The dynamical behavior of slow electrons traversing gases is to a large extent determined by two effects: the energy dependent evolution of the scattering phases for the relevant partial waves and the influence of temporary negative ion states (resonances). Some aspects of resonance and threshold phenomena are discussed. The theoretical description of electron-molecule collisions generally requires an adequate description of electronic, vibrational and rotational degrees of freedom. However, if the typical collision time is short compared to the rotational period, the molecule can be treated as having a fixed orientation during the collision process, and the result for the cross-section can be averaged over orientations. Treatment of vibrational dynamics is usually more important and more challenging to the theory. In the electron energy region important for applications, many inelastic processes such as vibrational excitation and dissociative electron attachment are driven by negative-ion resonances. The theoretical description of vibrational dynamics in these cases is usually based on the nonlocal complex potential describing the nuclear motion in the intermediate negative-ion state.

262 citations

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TL;DR: The relationship between the energy of activation (E*) and change in internal energy (ΔE) for the dissociative electron attachment reaction is uniquely linear with approximately a unit slope as discussed by the authors.

Abstract: Thermal electron attachment to several aliphatic fluoro, chloro, and bromo derivatives have been investigated in the range 30°–220°C and activation energies of 0–12 kcal have been determined The relationship between the energy of activation (E*) and change in internal energy (ΔE) for the dissociative electron attachment reaction is uniquely linear with approximately a unit slope Both chloro and bromo compounds apparently satisfy the same relationship This empirical relationship can be used to predict bond dissociation energies for aliphatic chloro, bromo, and iodo compounds from the energy of activation for thermal electron attachment Bond dissociation energies for 1,3‐dichloropropane, 1,2‐dibromoethane, and 1,3‐dibromopropane have been so determined as 756, 698, 709 kcal/mole, respectively An expression for a two‐dimensional representation of the potential‐energy curve for the negative ion is proposed with which the linear relationship between E* and ΔE can be derived The proposed potential‐energy curve is empirical, but contains only a single adjustable parameter characteristic of each compound

195 citations

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TL;DR: In this paper, the rate coefficients for the attachment reactions of electrons with CCl4, CCl3F, CHCl3, Cl2 and SF6 were measured under truly thermal conditions over the approximate temperature range 200-600K using a flowing-afterglow/Langmuir probe apparatus.

Abstract: The rate coefficients, beta , for the attachment reactions of electrons with CCl4, CCl3F, CCl2F2, CHCl3, Cl2 and SF6 have been measured under truly thermal conditions over the approximate temperature range 200-600K using a flowing-afterglow/Langmuir probe apparatus. The beta values obtained at 300K are 3.9*10-7, 2.6*10-7, 3.2*10-9, 4.4*10-9, 2.0*10-9 and 3.1*10-7 cm3 s-1 respectively. From the variation with temperature of beta for the CCl2F2, CHCl3 and Cl2 dissociative attachment reactions, activation energies, Ea, of 0.15, 0.12 and 0.05 eV respectively were derived. The beta for CCl4, CCl3F and SF6 are close to their theoretical limiting values within the temperature range investigated. While Cl- was the only product ion observed for the reactions involving chlorine-containing molecules, both SF6- and SF5- were observed for the SF6 reaction. The data obtained are compared with previous data and the separate influences of electron temperature and gas temperature are noted.

173 citations