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Hyperfine-Resolved Spectroscopy of Dysprosium Monoxide (DyO) for Precision Measurements of the Nuclear Schiff Moment

Zack D. Lasner, Aidan T. Ohl, Nicole M. Albright, Kendall L. Rice, Charlene Peng, Lan Cheng, John M. Doyle, Benjamin L. Augenbraun

TL;DR

This work addresses the search for time-reversal-violating physics via the nuclear Schiff moment by leveraging the high sensitivity of heavy nuclei in molecules. The authors perform high-resolution laser spectroscopy of DyO to resolve hyperfine structure in the X8 and [17.1]7 states for $^{161}$DyO and $^{163}$DyO, and extract magnetic and electric quadrupole hyperfine constants through a global fit to an effective Hamiltonian in Hund's case (c). The measured constants $h$ and $eQq_0$ show excellent agreement with state-of-the-art ab initio calculations (X2CAMF-CCSD(T)), validating the molecular model and providing essential benchmarks for future optical cycling and precision NSM experiments. The results establish DyO as a practical platform for NSM searches, enabling controlled cooling and long coherence times, and offer insights into short-range electronic wave functions that underpin symmetry-violating effects. The study also highlights remaining challenges in accurately predicting $eQq_0$ due to electronic polarization and state mixing, guiding future theoretical benchmarking.

Abstract

We perform laser spectroscopy of dysprosium monoxide (DyO) to determine the hyperfine structure of the ground X8 and excited [17.1]7 states in the $^{161}$Dy and $^{163}$Dy isotopologues. These dysprosium nuclei have non-zero nuclear spin and dynamical octupole deformation, which gives them high sensitivity to time-reversal-violating new physics via the nuclear Schiff moment (NSM). The DyO molecule was recently identified as being amenable to optical cycling -- the basis for many laser cooling and quantum control techniques -- which makes it a practical candidate for NSM searches. The measurements reported here are prerequisites to implementing optical cycling, designing precision measurement protocols, and benchmarking calculations of molecular sensitivity to symmetry-violating effects. The measured hyperfine parameters are interpreted using simple molecular orbital diagrams and show excellent agreement with relativistic quantum chemical calculations.

Hyperfine-Resolved Spectroscopy of Dysprosium Monoxide (DyO) for Precision Measurements of the Nuclear Schiff Moment

TL;DR

This work addresses the search for time-reversal-violating physics via the nuclear Schiff moment by leveraging the high sensitivity of heavy nuclei in molecules. The authors perform high-resolution laser spectroscopy of DyO to resolve hyperfine structure in the X8 and [17.1]7 states for DyO and DyO, and extract magnetic and electric quadrupole hyperfine constants through a global fit to an effective Hamiltonian in Hund's case (c). The measured constants and show excellent agreement with state-of-the-art ab initio calculations (X2CAMF-CCSD(T)), validating the molecular model and providing essential benchmarks for future optical cycling and precision NSM experiments. The results establish DyO as a practical platform for NSM searches, enabling controlled cooling and long coherence times, and offer insights into short-range electronic wave functions that underpin symmetry-violating effects. The study also highlights remaining challenges in accurately predicting due to electronic polarization and state mixing, guiding future theoretical benchmarking.

Abstract

We perform laser spectroscopy of dysprosium monoxide (DyO) to determine the hyperfine structure of the ground X8 and excited [17.1]7 states in the Dy and Dy isotopologues. These dysprosium nuclei have non-zero nuclear spin and dynamical octupole deformation, which gives them high sensitivity to time-reversal-violating new physics via the nuclear Schiff moment (NSM). The DyO molecule was recently identified as being amenable to optical cycling -- the basis for many laser cooling and quantum control techniques -- which makes it a practical candidate for NSM searches. The measurements reported here are prerequisites to implementing optical cycling, designing precision measurement protocols, and benchmarking calculations of molecular sensitivity to symmetry-violating effects. The measured hyperfine parameters are interpreted using simple molecular orbital diagrams and show excellent agreement with relativistic quantum chemical calculations.

Paper Structure

This paper contains 11 sections, 13 equations, 4 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Experimental Methods
  3. Observations
  4. Analysis
  5. Discussion
  6. Validity of the molecular parameters
  7. Interpretation of the Hyperfine Constants
  8. Magnetic Hyperfine Interaction
  9. Electric Quadrupole Interaction
  10. Ab initio calculations
  11. Conclusion

Figures (4)

  • Figure 1: Observed (black, upward-going) and simulated (blue, downward-going) spectrum of the [17.1]7$\leftarrow$X8 (0,0) P(9) branch features. Horizontal lines connect the sets of main ($\Delta F = -1$) peaks for the P branch. The individual hyperfine components are labeled by their values of $F$.
  • Figure 2: Observed (black, upward-going) and simulated (blue, downward-going) spectrum of the [17.1]7$\leftarrow$X8 (0,1) Q(8) branch features recorded at high laser power. Horizontal lines connect the sets of main and satellite transitions, which have $\Delta F = 0$ and $\Delta F=\pm1$, respectively, for the Q branch. The individual hyperfine components are labeled by their values of $F$.
  • Figure 3: Qualitative correlation diagram showing the ground-state electron configuration. Atomic energy levels for Dy and O are shown on the outside, ligand-field splittings are shown in gray in the intermediate region, and the resulting molecular orbital energy levels of DyO are given in the center.
  • Figure :