Mass Spectrometry: How Do Different Masses Have Same Velocity?

[ananthu]

When different masses are accelerated by the same potential,the lighter mass should move with a greater velocity than that of the heavier one. But, how in the velocity selector in the Bainbridge mass spectrometer, different masses(isotopes) come out with same velocity?

 

[NicholeHudson]

The velocity selector in the Bainbridge mass spectrometer follows the principal of deflection rather than the velocity. It explains that the ions are affected by the magnetic fields and then move in circular paths. The lighter ions move in the larger path radius and the heavier ones with a smaller radius. So you should check with the deflection rather that the speed of the particles as all the particles are rotated with the same speed. Hence radius is the only way to get the mass difference.