Sympathetic crystallization of CaH+produced by a laser-induced reaction

Abstract

We investigated sympathetic Coulomb crystallization of CaH${}^{+}$ ions produced by a laser-induced reaction through an excited state according to $^{40}\mathrm{Ca}$${}^{+}$($4p {}^{2}{P}_{1/2}$) $+$ ${\mathrm{H}}_{2}$ $\ensuremath{\rightarrow}$ $^{40}\mathrm{Ca}$H${}^{+}$ $+$ H. $^{40}\mathrm{Ca}$H${}^{+}$ ions stored in a linear Paul trap were characterized by their secular-motion excitation spectrum and by the modified fluorescence images of crystallized Ca${}^{+}$ ions. The number of two-species crystallized ions, the secular motion temperature, and the structure were determined by molecular dynamics simulations. Both the observed two-species ion crystals and simulation images demonstrate that the CaH${}^{+}$ ions were sympathetically crystallized with their secular-motion temperature being less than 10 mK. We determined reaction rates from fluorescence images of two-species Coulomb crystals by systematically changing the reaction time. In addition a lower limit for the reaction rate coefficient $k=8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$ cm${}^{3}$/s was obtained.