Photodetachment spectroscopy from cooled negative ions

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Photodetachment spectroscopy from cooled negative ions. Summer research in the AMO lab* June August 2005. James Wells. * Support from Davidson College and the American Chemical Society. -. -. -. -. -. +. +. -. -. -. -. Photodetachment. -. X - + photon X + e - - PowerPoint PPT Presentation

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  • Photodetachment spectroscopy from cooled negative ionsJames Wells

    Summer research in the AMO lab*June August 2005* Support from Davidson College and the American Chemical Society

  • Photodetachment- X- + photon X + e-

    Equivalent to latter half of an electron-atom collision.

  • Effects of ions random motionPhoton frequency is Doppler broadenedCauses uncertainty E in any energy-dependent measurementTypical experimental goal: measure probability of detachment as f(Ephoton)E blurs experimental results: fewer details, less contrast/structure.

  • Evaporative cooling

    Ions trapped in an ion trap: electrostatic potential well.

    Cooling applet

  • Ion trap apparatus

  • Ring dye laser

  • Laser LabVIEW control code(Screen shot)

  • Negative Ion Formation

    Short-range attractive potential (~ 2 eV deep and a few wide)

    Electron correlation effects partly responsible for covalent bonds

  • Energy Levels (Oxygen)

  • Photodetachment with B-Fields departing electron executes cyclotron motion in field

    motion in plane perpendicular to B is quantized to cyclotron levels

    cyclotron states separated by = eB/me

    motion along axis of field is continuous, non-quantized

    for typical B = 1.0 Tesla, 30 GHz, period = 36 ps

    quantized Landau levels add structure to detachment cross section

  • Trap electronics

  • Detachment cross section in B field

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