Answer 9.7

a) Name at least three methods of ion activation.

  1. Collision-induced dissociation (CID)
  2. Surface-induced dissociation (SID)
  3. Infrared multiphoton dissociation (IRMPD)
  4. Electron capture dissociation (ECD)
  5. Electron transfer dissociation (ETD)

b) Tell the differences between ion-neutral collision in the high-energy and in the low-energy regime.

In magnetic sector and TOF instruments, He is typically used as the collision gas because the energy transferred during (a single) high-energy collision (keV) is comparatively large; in addition He reduces the risk of charge exchange due to its high IE. In the low collision energy regime of quadrupole and ion trapping instruments (1-200 eV) Ar and Xe are frequently employed to make CID more effective due to multiple collision with those heavier atoms.

c) In IRMPD, how many photons from a continuous wave carbon dioxide laser of 10.6 µm wavelength do you need to increase the internal energy of an ion by about 3 eV?

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