We measured the total charge-transfer rate coefficients for ${\mathrm{C}}^{2+}$ with ${\mathrm{H}}_2,$ ${\mathrm{N}}_2,$ and CO using a cylindrical radiofrequency ion trap. ${\mathrm{C}}^{2+}$ ions were produced by the electron impact of residual CO in an ultrahigh-vacuum chamber. The rate coefficients for ${\mathrm{C}}^{2+}$ with ${\mathrm{H}}_2,$ ${\mathrm{N}}_2,$ and CO are measured to be $8.77\mathrm{}\left(0.71\right)\mathrm{}\times {10}^{-11}{\mathrm{cm}}^3{\mathrm{s}}^{-1}$ ${(T}_{\mathrm{equiv}}=2.63\mathrm{}\times {10}^3\mathrm{K}),$ $1.08\mathrm{}\left(0.07\right)\mathrm{}\times {10}^{-10}{\mathrm{cm}}^3{\mathrm{s}}^{-1}$ ${(T}_{\mathrm{equiv}}=1.17\mathrm{}\times {10}^4\mathrm{K}),$ and $4.58\mathrm{}\left(0.29\right)\mathrm{}\times {10}^{-10}{\mathrm{cm}}^3{\mathrm{s}}^{-1}$ ${(T}_{\mathrm{equiv}}=1.17\mathrm{}\times {10}^4\mathrm{K}).\mathrm{}$ The rate coefficient for ${\mathrm{C}}^{2+}$ with He is estimated to be less than ${10}^{-12}{\mathrm{cm}}^3{\mathrm{s}}^{-1}$ ${(T}_{\mathrm{equiv}}=4.38\mathrm{}\times {10}^3\mathrm{K}).\mathrm{}$

• Received 29 April 2003

DOI:https://doi.org/10.1103/PhysRevA.68.052704