Measurement of Kinetic Parameters of N₂⁺ Ions in a Paul Trap by RF Absorption Detection

We measured variations of the total number of N₂⁺ ions in a Paul trap versus applied dc voltage, and accordingly derived the mean kinetic energy and mean width of the spatial distribution of the ion cloud under the assumption of Gaussian model. The results are consistent with the theoretical values obtained from model calculations based on Brownian motion of trapped ions, and also compared with those derived by assuming uniform sphere distribution of ions.