## The stability diagram with some ions under trapping parameters used for this work

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**Figure 1.** The stability diagram with some ions under trapping parameters used for this work. The coordinates *a _{z}* and

*q*are dependent on the ion's

_{z}*m*/

*q*, the rf potential's frequency (Ω

_{0}), amplitude (

*V*

_{0}) and offset (

*U*

_{0}) as well as the trap's length and radius (2

*z*

_{0}and

*r*

_{0}). They are given by a_{z}=\displaystyle\frac{-16qU_{0}}{m\left(r_{0}^{2}+2z_{0}^{2}\right)\Omega _{0}^{2}}\quad { \rm and \quad }q_{z}=\frac{8qV_{0}}{m\left(r_{0}^{2}+2z_{0}^{2}\right)\Omega _{0}^{2}}. The ion's

*m*/

*q*value is also indicated. Only ions with

*m*/

*q*inside the region labelled stable will remain inside the trap. The first two sets of rf amplitude, frequency and dc offset, • and ▪, respectively, are used to eliminate the unwanted ions as

*m*/

*q*= 1, 2 and higher are placed well outside the stable regions. The eliminated ions will affect the intensity of the stored ion of interest (

*m*/

*q*= 1.5). In the final (third) set,, the ion of interest now free of the unwanted ions is stored under optimum conditions.

**Abstract**

We report our measured values for the sum of single and double charge transfer rate coefficients between ^{3}He^{2 +} and H_{2}, CH_{4}, N_{2} and CO. Our values are 2.4 ± 0.2 **×** 10^{−9} cm^{3} s^{−1} for H_{2}, 6.3 ± 0.9 **×** 10^{−9} cm^{3} s^{−1} for CH_{4}, 4.0 ± 0.3 **×** 10^{−9} cm^{3} s^{−1} for N_{2} and 4.7 ± 0.4 **×** 10^{−9} cm^{3} s^{−1} for CO. The values are obtained at equivalent temperatures of 1200–2400 K.