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Electron Attachment and Autodetachment in Metastable Molecular Anions: Analysis Techniques

This study examines electron attachment and autodetachment processes in metastable molecular anions, specifically focusing on the formation and decay of MX– ions. We highlight the efficiency of electron attachment at low energies, analyzing various methodologies including the diatomic model and vibrational energy redistribution (IVR). Key concepts like dissociative electron attachment (DEA) and stabilization mechanisms are explored. Analytical techniques utilized in this research include quadrupole mass filtering and collision region assessments, providing insights into intra- and intermolecular dynamics.

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Electron Attachment and Autodetachment in Metastable Molecular Anions: Analysis Techniques

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  1. Benni og rafeindirnar Sýnikennsla 7.mars 2014 Hópur III

  2. MX + e– MX–* MX + e– Electron attachment Autodetachment (AD) Electron attachment Dissociative electron attachment (DEA) M + X– Formation Decay MX–# Metastable molecular anion Stabilization through IVR Stabilization through IVR Attachment most efficient at low energies 2

  3. 0 Electron attachment Diatomic model AE Autodetachment Franck-Condon region MX–* 𝛔EA M + X Electron energy Potential Energy M + X– rc Internuclear distance 3

  4. Eth 0 AE Electron attachment Diatomic model BDE(MX) EA(X) Dissociative electron attachment (DEA) TH2 ≈ 7.5 fs TD2 ≈ 10.6 fs [1] MX–* 𝛔EA M + X Electron energy Potential Energy M + X– Eth = BDE(MX) – EA(X) rc Internuclear distance 4 [1] G. J. Schulz and R. K. Asundi. Phys. Rev., 158(1), (1967), 25.

  5. 0 Electron attachment Diatomic model Stabilization through intramolecular vibrational energy redistribution (IVR) MX– MX Electron energy Redistribution of energy to vibrational modes not relevant for AD Potential Energy Internuclear distance 5

  6. Methods SIGMA Acquisition SIGMA [1] PC Quadrupole mass filter Collision Region Channeltron Detector F2– / SF6 (m/z 38) TEM Ion intensity E Electron energy B 6 [1] E. H. Bjarnason, F. H. Ómarsson, M. Hoshino, H. Tanaka, M. J. Brunger, P. Limão-Vieira, and O. Ingólfsson, Int. J. Mass. Spectrom., 2013, 339-340, 45–53.

  7. Monochromatorinn • Hjarta tækisins, heimatilbúið • Rafeindabyssa skýtur lágorkurafeindum af stað í lofttæmi (eða því sem næst) • Þær reka áfram í stefnu segulsviðs, B, í gegnum raufir • Þær spíralla en ferðast ekki eftir beinni línu

  8. Monochromatorinn • Rafeindabunan kemur inn á TEM svæðið þar sem rafsvið, E, hornrétt á B tekur á móti henni • Segulsvið tækis er stöðugt en hægt er að breyta rafsviði • Þá taka rafeindirnar að „drifta“ samkvæmt hægrihandarreglunni • Þær „drifta“ mismikið eftir orku

  9. Monochromatorinn • Við hinn enda TEM svæðisins taka við fleiri raufir, sem búið er að hliðra miðað við fyrri raufir • Þannig er hægt að velja úr rafeindir • „útvöldu“ rafeindirnar halda síðan áfram og jóna sýnið (gas) • Jónaða sýnið er síðan greint með quadrupol massagreini

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