A 100 eV electron collides with a stationary helium ion (He + ) in its ground state and exits to a higher level. After the collision, He + ions emits two photons in succession with wavelength 1085 Å and 304 Å. Calculate the energy of the electron after the collision (in 10 –1 eV). Given h = 6.63 × 10 –34 Js.
Text Solution
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(5)
The energy of the electron in the
state of
ion of atomic number Z is given by
for
ion
. Therefore

The energies
and
of the two emitted photons in eV are

Thus total energy
Let
be the principle quantum number of exited state. Now we have for the transition from
to 

But
. Therefore 

Which gives
or
The energy of the incident electron
(given). The energy supplied to
ion
.
Therefore, the energy of the electrons left after the collision
.
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