Optical Mass Spectrometry of Cold $\mathrm{RaOH}^+$ and ${\mathrm{RaOCH}_3}^+$

Abstract

We present an all-optical mass spectrometry technique to identify trapped ions. The new method utilizes laser-cooled ions to determine the mass of a co-trapped dark ion with sub-dalton resolution within a few seconds. We apply the method to identify the first controlled synthesis of cold, trapped RaOH + and RaOCH3 + . These molecules are promising for their sensitivity to time and parity violation that could constrain sources of new physics beyond the standard model. The nondestructive nature of the mass spectrometry technique may help identify molecular ions or highly charged ions prior to optical spectroscopy. Unlike previous mass spectrometry techniques for small ion crystals that rely on scanning, the method utilizes a Fourier transform which is inherently broadband and comparatively fast. The technique's speed provides new opportunities for studying state-resolved chemical reactions in ion traps.

Searches for new sources of CP violation using molecules as quantum sensors

“…Experiments are also under construction with the goal of searching for hadronic CPV by leveraging the advantages which allowed molecular eEDM searches to become the most sensitive. These include the CENTReX nuclear Schiff moment search in a beam of TlF [29], a numagnetic quadrupole moment search in a beam of 173 YbOH [30][31][32][33], and experiments with radioactive RaF [34] and RaOCH + 3 [35,36] discussed in a later section. These experiments are in parallel to improvements of existing atomic searches with 199 Hg [12], 225 Ra [37,38], and 129 Xe [39,40], and development of new experiments such as matrix-isolated 229 Pa [41].…”

“…RaF was recently spectroscopically studied [34], and along with polyatomic analogues offer laser cooling and extreme sensitivity to hadronic symmetry violations. RaOCH + 3 , which was recently synthesized, trapped and cooled in an ion trap [35], offers similar sensitivity with the possibility for an experiment with advanced ion control techniques [9,35,36,72].…”

Probing Fundamental Symmetries of Deformed Nuclei in Symmetric Top Molecules

“…We briefly consider the hyperfine structure for 226 RaOCH + 3 in the |N = 1, |K| = 1 manifold, which yields 12 unique levels. This is the isotopologue recently produced in an ion trap [35], and could serve as a valuable platform for spectroscopy and development. As the 226 Ra nucleus is spin-0, the only hyperfine term to consider is the spin-rotation interaction between the orthohydrogen state and the molecular rotation, and the hyperfine basis reduces to |N, K, S, J, m J |Γ, I H , m IH with the radium spin terms omitted.…”

“…In this manuscript, we consider a symmetric top molecule (STM), the radium monomethoxide cation (RaOCH + 3 ), as a platform to combine nuclear and molecular enhancements with the advantages of a polyatomic structure and extended coherence time achievable with an ion trap. This molecule, which was recently produced and co-trapped [35] with laser-cooled Ra + [36], has axial symmetry that gives rise to near-degenerate opposite parity K-doublets, thereby enabling full polarization in small fields and the co-magnetometer states necessary for sensitive measurements in an ion trap. The ground electronic state ( X1 A 1 ) is diamagnetic, suppressing sensitivity to magnetic noise.…”

“…Over the years, a wide variety of metal-monohydroxide (MOH + ), metal-monomethoxide (MOCH + 3 ), as well as dual-metal hypermetallic (MOM + ) ions have been created [79,80] (and, in some cases, trapped [81,82]), including species with heavy nuclei such as Ba [81] and Lu [80] in addition to Ra [35]. The rich internal complexity of these molecules makes them attractive for a broad range of studies not limited to Schiff moment measurements [1].…”