Abstract
A laser induced reaction technique (LIR) was used to determine kinetic temperature of N2+ ions trapped in a 22-pole RF trap. Described are the measurements of translation temperature of N2+ ions stored in the trap cooled down to 10 K.
As the monitor reaction we used endothermic charge transfer $N_2^+ + Ar \rightarrow Ar^+ + N_2$. Rate coefficients for ground state of N2+ and for states excited with laser are different.
The kinetic energy of N2+ ions was determined from Doppler broadening of measured spectral lines in Meinel band ($X^2\Sigma_g^+, \nu‘‘ = 0 \leftarrow A^2\Pi_u^+, \nu‘ = 2$). The experiments show cooling of trapped N2+ ions in collisions with helium buffer gas.
Parameters of the apparatus, further improvements of ion trapping and cooling and calibrations are discussed.