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   Convert electron volts to velocity.

   Type EVToV for a demo.
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   Form:
   v = EVToV( atom, eV )
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   ------
   Inputs
   ------
   atom          {:}    Atom name see AtomicMass
   eV            (1,:)  Energy (eV)
          

   -------
   Outputs
   -------
   v             (1,:)  Velocity (km/s)
   
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