Collaborative Research: Molecular Platforms for Studies of Parity Non-conservation and Novel Bonding Mechanisms

About This Grant

With support from the Chemical Structure and Dynamics (CSD) program in the Division of Chemistry, Professor Michael Heaven at Emory University and Professor Richard Mawhorter at Pomona College are conducting gas phase high-resolution molecular spectroscopy measurements of candidate molecules to probe their potential to advance the search for physics beyond the standard model (BSM). The remarkably successful standard model cannot explain the imbalance of matter and anti-matter in the universe. Violations of molecular symmetry properties, detected by precision spectroscopic measurements, can provide critical tests of proposed BSM theories. One challenge for this approach is that the molecules must be cooled to nearly absolute zero (ultracold) to achieve the required measurement accuracy. A second challenge is that the BSM effects will be largest for molecules that include a heavy atom. Such molecules usually exhibit congested and complicated spectra. Consequently, many theoretically promising molecules have not been characterized in laboratory studies. Professors Heaven, Mawhorter and their students will carry out experimental studies of three classes of heavy element-containing molecules. The objectives are to identify the most promising candidates for BSM measurements and to obtain the spectroscopic data needed for the design of the experiments as well as to determine how to accomplish the cooling, state preparation and state read-out. The educational impact of this program is that it provides excellent training for graduate students, and research experience opportunities for undergraduate students. The experiments involve advanced instrumentation, and interpretation of the results requires the application of high-level theoretical methods. Several laser-based spectroscopic instruments will be applied. The available techniques include laser induced fluorescence, dispersed laser induced fluorescence, two-photon ionization and anion photodetachment. The first group of molecules to be examined is YbNH2, YbCH3 and YbSH. Preliminary data for YbNH2 and YbCH3, and calculations for YbSH indicate that they are promising for direct laser cooling. Electronic transition energies, fluorescence branching ratios and low energy metastable states will be characterized. The second group of molecules, YbF- and the group IIA oxyfluoride anions (OMF-) may be cooled using external electric fields and then converted to neutral molecules by means of photodetachment. For this scheme the bond dissociation energy of the anion must exceed the electron affinity of the neutral. Tests for this condition will be conducted using anion photodetachment spectroscopy. Lastly, diatomic molecules consisting of Cu, Ag or Au bound to Yb will be examined. These molecules may be formed at ultracold temperatures by photoassociation. The spectroscopic data needed for the design of such ultracold synthesis experiments will be sought using laser ablation techniques to generate the target molecules at higher temperatures (5-20 K). This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.