2-4 Tuning the instrument
4. On the Control 1 tab, set both Source Slit and Collector Slit to 100.00 to
open the slits fully.
Tip: If you type the values into the text boxes, rather than using the
sliders, press the keyboard return key after entering each value.
5. In the Control 2 tab, set Alpha Slit to 100.00 to open the slit fully.
6. In the Control 1 tab, set Magnet Mass to 28.
Rationale: Doing so sets the magnet to detect atmospheric nitrogen (N
2
).
7. Beneath the display, set Span (ppm) to 100000.
Rationale: Doing so increases the mass window range displayed on the
Tune window peak display by scanning the accelerating voltage over a
larger range.
Result: The nitrogen peak appears in the Tune window peak display.
Unless you have already correctly tuned the instrument, the peak
appears near, but not at, its correct value of 28. You must calibrate the
mass scale in order to correct this value.
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