Flight-path constant

In a preliminary pulsed-laser atom-probe measurement,158 the critical ion energy deficits of Rh and W atoms, field evaporated from kink sites, are measured at a rate of 1010 layers per second at a temperature around 100 K. Using the system constants, i.e. the flight path constant and the... 

Fig. 3.19 Mass separated energy distributions of pulsed-laser field desorbed 4He+ and ions obtained with the Penn State pulsed-laser ToF atom-probe when the flight path length was 778 cm. Their onset flight times are separated by 34 ns, exactly that calculated from the system constants and their critical ion energy deficits at 5.5 kV.

Here, k = 1.38 10 J/K is Boltzmann s constant. Since the overall flight path L in a mass spectrometer must be smaller than the mean free path if the ions are to transit successfully, the operating pressure must be... 

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