Question

Suppose you build a TOF mass spectrometer that accelerates ions to an energy of 1000 eV. The overall length of the flight path is 2.0 meters. If you want to cover a mass range up to 15,000 Daltons, and you want to ensure that a mass spectrum is completely recorded before the next spectrum begins, at what frequency can you pulse your ion source?

Answer 1

SOLUTION~~

In effect, the potential energy is converted to kinetic energy, meaning that equations of p.e and k.e must be equal-

E_p = E_k

Ep=1000 eV

Ek= mv²/2                                                                  ( mass = 15000 dalton; where 1 dalton=1.66X10^-27 )

therefore by solving :-

1000= 1.66X10-27 x v² /2

v² = 1.2 X 10³⁰

v= 1.1 X 10¹⁵

Now , time = d/v ; where d= length of flight path

t= 2/(1.1 X 10¹⁵⁾

^{as we know frequency = 1/time}

^therefore

frequency = 1.1 X 10¹⁵ / 2

frequency = 0.55 X 10¹⁵