[edwin brooke]

Sorry for that,I have already known the answer.
Here I have another question,which is also related to the mass spectrometry.
In the ionisation chamber,high speed electrons from electron gun knock electrons off the atoms or molecules being analysed,and change them into cations.
We can use a equation to conclude the above:
       X(g)+fast e- ------> X+(g) + 2 slow e-
(a)From the above equation,we apply conservation of momentum,
    mava = mbvb
    where ma and mb is the mass of e-,va is the velocity of e- from electron gun,vb is the velocity of e- from
    the atom/molecule in the sample.
    ma = mb
    va > vb
    That means momentum is not conserved?
(b)Sometimes,ions with charges higher than 1+ are formed,why?

[Arkcon]

(b)Sometimes,ions with charges higher than 1+ are formed,why?

Are ions of greater than +1 ever formed by some other mechanism, as in not in an instrument?  For example, what ions odes CaCl₂ form in water?

[edwin brooke]

sorry it should be maua + mbub = mava + mbvb
I have made a silly mistake ,I mixed the above equation with the equation appears in molarity,

Yes,CaCl2 is soluble in water and it becomes mobile ions when dissolves in water,forming Ca2+ and 2Cl-.
But in here,e- from electron gun knocks out e- from atom or molecules of the sample.I can't understand.
Usually 1 e- is lost from the atom,but sometimes 2 e- are lost?But not higher?What affects the no of e- lost in the ionisation?

[Arkcon]

Sometimes the ion gun transfers more than one electron to the ionized molecule because ... sometimes the ion can hold more than one electron.  Its not really more complicated than that.