Chiral molecule candidates for trapped ion spectroscopy byab initiocalculations: From state preparation to parity violation

Abstract

Parity non-conservation (PNC) due to the weak interaction is predicted to give rise to enantiomer dependent vibrational constants in chiral molecules, but the phenomenon has so far eluded experimental observation. The enhanced sensitivity of molecules to physics beyond the Standard Model (BSM) has led to substantial advances in molecular precision spectroscopy, and these may be applied to PNC searches as well. Specifically, trapped molecular ion experiments leverage the universality of trapping charged particles to optimize the molecular ion species studied toward BSM searches, but in searches for PNC, only a few chiral molecular ion candidates have been proposed so far. Importantly, viable candidates need to be internally cold, and their internal state populations should be detectable with high quantum efficiency. To this end, we focus on molecular ions that can be created by near threshold resonant two-photon ionization and detected via state-selective photo-dissociation. Such candidates need to be stable in both charged and neutral chiral versions to be amenable to these methods. Here, we present a collection of suitable chiral molecular ion candidates we have found, including CHDBrI+ and CHCaBrI+, that fulfill these conditions according to our ab initio calculations. We find that organo-metallic species have low ionization energy as neutrals and relatively high dissociation thresholds. Finally, we compute the magnitude of the PNC values for vibrational transitions for some of these candidates. An experimental demonstration of state preparation and readout for these candidates will be an important milestone toward measuring PNC in chiral molecules for the first time.

Mathieu-Hill Equation Stability Analysis for Trapped Ions. Anharmonic Corrections for Nonlinear Electrodynamic Traps

“…On the other hand, it was demonstrated that an increased dodecapole potential generated in an asymmetric linear ion trap (LIT) [97] opens new pathways for exciting applications in mass spectrometry or Coulomb crystals. Such a setup also enables dark ion (inappropriate confined species) elimination from a trapped ion-chain consisting of physical qubits [47], or performing searches for time and parity violations that could constrain sources of new physics BSM [83,110,111].…”

Large vibrationally induced parity violation effects in CHDBrI+

“…Since such molecules have a neutral precursor, the molecular ion may be susceptible to predissociation in a vibrational spectroscopy experiment due to a low dissociation threshold. However, the two hydrogen isotopes in CHDBrI + give rise to a high dissociation threshold with a value of 1.29 eV as opposed to other halogenated methanes along with the high transition state energy between enantiomers of 1.3 eV, indicating that long lifetimes should be accessible for this candidate, 1 while tunneling effects should be negligible. Moreover, the proposed state preparation and detection methods for CHDBrI + through near-threshold, state-selective photo-ionization suggest that its preparation in an internally cold state is possible, improving the contrast in a future measurement.…”

“…The latter system was proposed as a promising candidate for future high-precision laser spectroscopy experiments on trapped ions, due to a number of experimental advantages. 1 This proposal follows recent successful precision measurements on ionic systems, such as the molecular ion eEDM (electron electric dipole moment) measurement, 36 and quantum logic spectroscopy of molecular ions. 37,38…”

“…1, showing surprisingly large PV effects in several of the (chiral) vibrational modes. CHDBrI + was proposed as a candidate for precision spectroscopy in Landau et al 1 In stark contrast to exotic designer molecules that contain heavy atoms, 23–27 the CH 2 BrI molecule family plays an important role in atmospheric chemistry and is naturally produced in plankton. 33 The PV effect of CHDBrI + is by far the largest ever computed amongst such molecules 34,35 and therefore is of great significance toward gauging the importance of the weak interaction in chemistry in addition to being a promising candidate for future PV measurement using trapped ion laser spectroscopy.…”

“…Moreover, the proposed state preparation and detection methods for CHDBrI + through near-threshold, state-selective photo-ionization suggest that its preparation in an internally cold state is possible, improving the contrast in a future measurement. 1 Finally, CH 2 BrI is a commercially available product, indicating that a species-wise pure racemic sample of CHDBrI could be enriched and large values of N should be expected in a single shot of the experiment.…”