Mass Spectrometer: Separating Isotopes

Theory

Ions enter a uniform magnetic field with the same speed $v$ and charge $q$. Each one follows a semicircle of radius $r=\frac{mv}{qB}$, so heavier ions land farther away. The landing distance $2r$ reveals the mass — the principle used to identify isotopes.

What to observe

• Masses in the ratio 1 : 1.5 : 2 land at distances in the same ratio.

Try this

• Increase B: all semicircles shrink.
• Give one ion a negative charge: it curves the other way.

Also available in: Espectrômetro de massa: separando isótopos (Português) · Espectrómetro de masas: separando isótopos (Español)