Detecting the internal state of polar molecules is a substantial challenge when standard techniques such as resonance-enhanced multi photon ionization (REMPI) or laser-induced fluorescense (LIF) do not work. As this is the case for most polyatomic molecule species, we here investigate an alternative based on state selective removal of molecules from an electrically trapped ensemble. Specifically, we deplete molecules by driving rotational and/or vibrational transitions to untrapped states. Fully resolving the rotational state with this method can be a considerable challenge as the frequency differences between various transitions is easily substantially less than the Stark broadening in an electric trap. However, making use of a unique trap design providing homogeneous fields in a large fraction of the trap volume, we successfully discriminate all rotational quantum numbers, including the rotational M-substate.
Infrared absorption spectroscopy of a single polyatomic molecular ion
Institut für Experimentalphysik, Universität Innsbruck（因斯布鲁克大学实验物理研究所）；Department of Optics, Palacký University（帕尔察基大学光学系）；Faculty of Physics, University of Warsaw（华沙大学物理学院）
High-sensitivity molecular spectroscopy of SrOH using magneto-optical trapping
Harvard-MIT Center for Ultracold Atoms（哈佛-麻省理工学院超冷原子中心）；Department of Physics, Harvard University（哈佛大学物理系）；University of California, Berkeley（加州大学伯克利分校）；IonQ, Inc.（IonQ公司）
