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Experimental Study on Electron Impact Double Ionization Dynamics for Atomic and Small Molecular Targets at Intermediate Incident Energy Chengjun Li

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Experimental Study on Electron Impact Double Ionization Dynamics for Atomic and Small Molecular Targets at Intermediate Incident Energy Chengjun Li Experimental study on electron impact double ionization dynamics for atomic and small molecular targets at intermediate incident energy Chengjun Li To cite this version: Chengjun Li. Experimental study on electron impact double ionization dynamics for atomic and small molecular targets at intermediate incident energy. Other [cond-mat.other]. Université Paris Sud - Paris XI, 2013. English. NNT : 2013PA112055. tel-00867037 HAL Id: tel-00867037 https://tel.archives-ouvertes.fr/tel-00867037 Submitted on 27 Sep 2013 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. UNIVERSITE PARIS-SUD Ecole Doctorale Ondes et Matière Institut des Sciences Moléculaires d‟Orsay DISCIPLINE Physique THÈSE DE DOCTORAT soutenue le 25/04/2013 par Chengjun LI Experimental study on electron impact double ionization dynamics for atomic and small molecular targets at intermediate incident energy Directeur de thèse: Elena-Magdalena STAICU-CASAGRANDE MdC(HDR) (Université Paris Sud XI) Composition du jury : Président du jury : Christophe BLONDEL DR (Université Paris Sud XI) Rapporteurs : Ugo ANCARANI MdC (HDR) (Université de Lorraine) Amine CASSIMI Ingénieur (HDR) (CEA, Caen) Examinateurs : Arne KELLER Professeur (Université Paris Sud XI) Pascal LABLANQUIE DR (Université Pierre et Marie CURIE) Membres invités : Azzedine BENNANI Professeur (Université Paris Sud XI) Contents General introduction……………………………………………………………………………………5 Chapter 1 Theory of electron impact double ionization and motivation of experimental investigation 1.1 Introduction…………………………………………………………………………………………..9 1.1.1 Electron impact ionization process……………………………………………………...9 A. Structure studies……………………………………………………………………...10 B. Collision dynamical studies………………………………...……………………...11 C. Electron impact double ionization………………………………...……………...11 1.1.2 Definition of different n-fold differential cross sections…………………………..12 A. Single differential cross section……………………………………………………12 B. Double differential cross section…………………………………………………..12 C. Triple differential cross section…………………………...………………………13 D. Four-fold and five-fold differential cross section………………………………13 1.2 Collision theory of double ionization………………………...…………………………….14 1.2.1 Perturbative theory………………………………………………………………………..15 A. Dynamical ionization mechanism for atomic target…………...………………15 B. Theoretical models for molecular dynamical ionization process……...……17 1.2.2 Non-perturbative theory………………………………………………………………….19 A. Convergent close coupling………………………………………………….………19 B. Exterior complex scaling…………………………………...………………….……20 C. Time-dependent close-coupling……………………...………………………….…20 1.3 Three double ionization mechanisms …………………...…………...…………………….21 A. Shake Off………………...………………………………………………...…………...21 B. Two-Step 1………………...………………………………………………...…………21 C. Two-Step 2………………...………………………………………………...…………22 1.4 Motivation of experimental study of double ionization…………………………….23 - 1 - 1.5 Bibliography……………...………………………………………………...……………………….26 Chapter 2 Experimental Apparatus 2.1 General presentation of the setup……………………………………………...……………31 2.2 Vacuum system………...………………………………………………...…………………………33 2.3 Electron beam system.………………………………………………...…………………………34 2.3.1 Electron gun and electrostatic lens system………………………………...…………34 2.3.2 Beam Stop and pin-hole………………………………...…………………………..……35 2.4 Gas source and collision volume…………...……………………………...…………………36 2.5 Three toroidal analyzers……………………...………………………………...………………37 2.5.1 Twin toroidal analyzers……...………………………………...…………………………38 2.5.2 „A-toroidal‟ analyzer……………………………...……………………………….……...40 2.6 Position sensitive detectors and coincidence technique ………………………..……42 2.6.1 Position Sensitive Detector…………………….………………………….…………….42 A. Micro Channel Plate …………….…………………………………….………..42 B. Resistive anode and position signal……………………………….…….…...43 C. Time signal…………………….………………………….………………………45 2.6.2 Double and triple coincidence technique in (e, 2e)/(e, 3-1e)/(e, 3e)……………45 2.7 Data analysis procedure…………….…………………………….…………………………….47 2.7.1 Experimental data exploitation…………………………………………………………47 2.7.2 Quantitative analysis……………………………………………………………………...52 2.8 Calibration and experimental procedure………………………………………………...57 2.8.1 Energy calibration and energy resolution……………………………………………..57 2.8.2 Angular Calibration…………………………………………………………………….…62 2.8.3 Validation of the experimental procedure……………………………………………64 2.9 Bibliography………………………………………………………………………………………...66 Chapter 3 Coplanar asymmetric (e, 3-1e) measurements on He, Ne and Ar atoms: predominance of the second-order, two- step mechanism - 2 - 3.1 Introduction…………………………………………………………………………………………68 3.2 Details of theory used for comparison…………………………………………………….69 3.2.1 First Born Approximation Three Coulomb waves and First Born Approximation with Two Coulomb waves plus Gamow factor……………….....70 3.2.2 Second Born approximation model and Second Born approximation with two Coulomb functions plus Gamow factor……………………………………………….72 3.2.3 The Two Step 2-Monte Carlo Event Generator……………………………………..73 3.3 Experimental conditions and calibration………………………………………………...75 3.4 (e, 3-1e) results and discussion………………………………………………………………..76 3.4.1 General observation and comparison with theoretical calculation………………81 A. (e, 3-1e) results discussion of He………………………………………………….81 B. Discussion of Ne and Ar (e, 3-1e) results………………………………………..83 3.4.2 TS2 kinematical analysis………………………………………………………………...87 A. Including only the binary contribution……………………………………...87 B. Including both binary and recoil contribution…………………………….89 C. TS2 kinematical analysis including both binary and recoil contribution in equal energy sharing case………………………………………………….99 3.5 Conclusion…………………………………………………………………………………………..99 3.6 Bibliography……………………………………………………………………………………….101 Chapter 4 (e,3-1e) and (e,3e) measurements for N2 at intermediate impact energy: identification of first order and non- first order contributions 4.1 Introduction……………….……………….……………….……………….………………….….106 4.1.1 Overview of previous works on electron impact ionization of molecular targets……………….……………….……………….………………..………………….….106 4.1.2 Description of the theoretical model for molecular double ionization.…………107 4.1.3 Two Step-2 kinematical model for double ionization of N2 …….………………...108 4.2 Results and discussion……….……………….……………….………………..………………109 4.2.1 Experimental conditions…………….………………………….………………………...109 - 3 - 4.2.2 (e,3-1e) asymmetric and symmetric coplanar measurements……………….…….110 4.2.3 (e,3e) symmetric coplanar measurements…….………………………….…………...118 A. General analysis with TS2 kinematical model……………………………..118 B. Discussion of Schematic emission diagrams………………………….……123 C. Different cuts mode discussion………………………………………………..128 4.3 Conclusion…………………………………………………………………………………………..137 4.4 Bibliography……………………………………………………………………………………….138 Chapter 5 Preliminary results for Ne and CH4 at intermediate incident energy 5.1 Experimental conditions………………………………………………………………………142 5.2 Results and discussion………………………………………………………………………….143 5.2.1 General observations………………………………………………………………………143 5.2.2 TS2 kinematical model analysis………………………………………………………...147 5.2.3 Influence of target nature on (e, 2e) and (e, 3-1e) results………………………….149 5.3 Conclusion………………………...………………………………………………………………..153 5.4 Bibliography……………………….…….…………………………………………………………154 Conclusion and perspectives ………………………………………………………………..……155 - 4 - General introduction The single or multiple ionization of atoms (or molecules) by charged particle (or by photon) impact is one of the most interesting and most important domains in atomic physics [1, 2]. The electron impact ionization is among the most fundamental cases of such processes. The detailed knowledge of the single ionization (SI) and double ionization (DI) is strongly needed in other physics branches such as plasma physics, astrophysics, where the basic interaction mechanisms – ionization, excitation, electron capture, etc. – are involved. It is also needed in other sciences such as biology science, where the prime importance is to understand the various mechanisms leading to energy deposition by radiation in living matter [3]. From the study of single or double ionization by electron impact, depending on different kinematical regimes, we can obtain fundamental information on two aspects: (a) dynamical information on SI or DI process such as projectile-target interaction, electron-electron correlation, post-collision interaction (PCI), etc.; (b) target structure information using the so-called electron momentum spectroscopy (EMS). In this work, we mainly focus on the experimental investigation of electron impact DI dynamics at intermediate incident energy for atomic targets and small molecular targets. To this purpose, we use the so-called (e,3e) and (e,3-1e) experiments which yield very detailed information in the form of fully differential cross sections. The (e, 3e) experiments refer to electron impact DI experiments in which the scattered projectile and the two target ejected electrons are selected and analyzed in energy and direction and are detected
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