Delayed and Pulsed Ion Extraction with Desorption Techniques

Combining Delayed and Pulsed Ion Extraction with Desorption Techniques 

FIGURE 7.4 (a) Schematic diagram of the infrared laser desorption (IRLD) time-of-flight mass spectrometer with time-delved ion extraction, and (b) timing diagram. (Reprinted with permission from reference 15). 

Passive Ion Storage. The IRLD instrument was constructed from a modified CVC Products (Rochester, NY) model 2000 time-of-flight mass spectrometer, a Wiley-McLaren design that included a pulsed electron beam. When used in the electron impact (El) ionization mode it was possible to monitor the NJ ion signal as a fimction of the electron-beam pulse width from 0.1 ps (where the signal was proportional to the pulse width) to 3 (is (where losses due to ion drift from the source equal the rate of ion production). From this, one could determine the rate of ion loss from the extraction volume due to drift at thermal energies. For the N2 ion (wj/z = 28) the half-life in the extraction volume was about 1 ps. Since the drift velocity is  

FIGURE 7.6 Schematic of a delayed-extraction MALDI-TOF mass spectrometer. (Reprinted with permission from reference 18). 

---