Molecular Spectroscopy by Coherent Motion Detection

We are currently constructing an experiment to perform spectroscopy on single trapped molecular ions. A silicon monoxide molecular ion (SiO$^{+}$) will be co-trapped with a barium ion in a linear Paul trap. The barium ion is laser-cooled and sympathetically cools the molecular ion; rotational cooling of SiO$^{+}$ will be accomplished by P-branch optical pumping on the B-X electronic transition. The spectroscopy result of the molecular ion is mapped to the barium ion through a state-dependent coherent motional state excitation. We are particularly interested in probing rotational (microwave) or vibrational (infrared) transitions sensitive to a time-varying electron-to-proton mass ratio.