CHEM 205 Lecture Notes - Ion Source, Impact Ionization, Photoionization
Document Summary
2 methods of ionization: photoionization: m + hf=m+, e-, fragments via pi, elecron impact ionization: m +e- m+, 2e- fragments via ei. 2 methods of mass separation: magnetic field: f=evb, electric field: f=ee, for both, the acceleration of the particle will be f=ma, **e=electric field=voltage/distance. In an electric field (more common): the lighter particles accelerate more, hits detector before the heavier particles. In magnetic field: the magnet induces a change in direction of the fragment. Smaller radius=less mass=smaller curve: in magnetic field, radius~m0. 5. Interpreting mass spectrometry graph: highest peak=molecular ion peak (m+)--usually, also have isotope and base peaks (?, see examples on ppt lecture 25. Have 3 possible combinations: small possibility of cl coming off and br staying: 2 peaks at 107, 109. Large possibility of br coming off (larger mass), giving characteristic 3:1 peak: and also large possibility of both cl, br coming off.
