Mass-to-charge ratio

Mass-to-charge ratio
Common symbols	m/Q
SI unit	kg/C
In SI base units	kg⋅A−1⋅s−1
Dimension	${\displaystyle {\mathsf {MI^{-1}T^{-1}}}}$

The mass-to-charge ratio (m/Q) is a physical quantity relating the mass (quantity of matter) and the electric charge of a given particle, expressed in units of kilograms per coulomb (kg/C). It is most widely used in the electrodynamics of charged particles, e.g. in electron optics and ion optics.

It appears in the scientific fields of electron microscopy, cathode ray tubes, accelerator physics, nuclear physics, Auger electron spectroscopy, cosmology and mass spectrometry.^[1] The importance of the mass-to-charge ratio, according to classical electrodynamics, is that two particles with the same mass-to-charge ratio move in the same path in a vacuum, when subjected to the same electric and magnetic fields.

Some disciplines use the charge-to-mass ratio (Q/m) instead, which is the multiplicative inverse of the mass-to-charge ratio. The CODATA recommended value for an electron is Q/m = −1.75882000838(55)×10¹¹ C⋅kg⁻¹.‍^[2]