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Benni og rafeindirnar

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

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Benni og rafeindirnar

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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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