Trapping, Cooling, and Photodissociation Analysis of State-Selected H2+ Ions Produced by ( 3+1 ) Multiphoton Ionization

We report on the production of cold, state-selected ${\mathrm{H}}_{2}^{+}$ molecular ions in a linear rf trap. The ions are produced by ($3+1$) resonance-enhanced multiphoton ionization (REMPI) of ${\mathrm{H}}_{2}$, and sympathetically cooled by laser-cooled ${\mathrm{Be}}^{+}$ ions. After demonstrating and characterizing the REMPI process, we use photodissociation by a deep UV laser at 213 nm to verify the high vibrational purity of the produced ${\mathrm{H}}_{2}^{+}$ ion samples. Moreover, the large difference between the photodissociation efficiencies of ions created in the $v=0$ and $v=1$ levels provides a way to detect a $v=0\ensuremath{\rightarrow}1$ transition. These results pave the way towards high-resolution vibrational spectroscopy of ${\mathrm{H}}_{2}^{+}$ for fundamental metrology applications.