arXiv subjects

Nicholas R. Hutzler

Publications and source records attributed to Nicholas R. Hutzler.

At least 19 recordsLinked to original sources

arXiv2026

Probing $P,T$-Symmetry Violation with Optically Trapped Asymmetric Top Molecules

Searches for $P,T$-violating electromagnetic moments are among the most sensitive probes of physics beyond the Standard Model. Extending beyond current limits will benefit from molecules with fully controllable orientation at low electric fields, long coherence times, and laser coolability---all offered by asymmetric top molecules (ATMs). Exploiting the intrinsic rotational $K$-doubling in ATMs and the associated long-lived ($T_1 \gtrsim 10$ s) parity doublets afforded by $C_{2v}$ symmetry and nuclear-spin statistics, these species combine large electric polarizability with long coherence times in modest laboratory fields. We study alkaline-earth(-like) monoamides, $\mathcal{M}$--NH$_2$ ($\mathcal{M}$ = Ca, Sr, Ba, Yb, Ra), which possess favorable electronic structure for laser cooling. We perform \textit{ab initio} calculations of fine and hyperfine constants, identifying the importance of relativistic effects in the spin-rotation tensor. An effective Hamiltonian then models the rotational and hyperfine structure of the vibronic ground state, quantifying electron electric dipole moment (EDM) sensitivities and identifying feasible measurement schemes. We compute the effect of external fields and identify engineered clock transitions that suppress sensitivity to external perturbations while retaining strong EDM sensitivity, and characterize the magic trapping conditions that null differential light shifts in an optical trap. Under these conditions we project a statistical electron-EDM sensitivity over an order of magnitude beyond current best experimental limits, with further gains available from increased molecule number and coherence time. Our results establish asymmetric top molecules as a tunable platform for sensitive symmetry-violation measurements with long coherence times.

physics.atom-ph↗

arXiv2026

Production and spectroscopy of cold radioactive molecules

Molecules with heavy, radioactive nuclei promise extreme sensitivity to fundamental nuclear and particle physics. However, these nuclei are available in limited quantities, which challenges their use in precision measurements. Here we demonstrate the gas-phase synthesis, cryogenic cooling, and high-resolution laser spectroscopy of radium monohydroxide, monodeuteroxide, and monofluoride molecules ($^{226}$RaOH, $^{226}$RaOD, and $^{226}$RaF) in a tabletop apparatus by combining novel radioactive target production protocols, optically driven chemistry in a cryogenic buffer gas, and low-background spectroscopic detection methods. The molecules are cooled in the lab frame, creating conditions that are the same starting points as many current molecular precision measurement and quantum information experiments. This approach is readily applied to a wide range of species and establishes key capabilities for molecular quantum sensing of exotic nuclei.

physics.atom-ph↗

arXiv2025

Engineered Molecular Clock Transitions for Symmetry Violation Searches

Heavy polar molecules are sensitive probes of physics Beyond the Standard Model. However, uncontrolled external electromagnetic fields pose challenges to achieving precise and accurate measurements. Minimizing susceptibility to these fields is therefore critical and has played an important role in all precision experiments of this type. Here we devise and demonstrate clock transitions engineered to realize robust symmetry violation searches in the polyatomic molecule YbOH. Sensitivities to external fields can be suppressed by orders-of-magnitude while preserving high sensitivity to the electron electric dipole moment (eEDM). We perform Ramsey measurements on these clock transitions and observe suppression of electric and magnetic sensitivities by at least a factor of 700 and 200, respectively, and demonstrate the robustness of their spin coherence against large electromagnetic field fluctuations. We further identify and employ selected quantum states to make sensitive measurements of external magnetic and electric fields, another critical feature for highly accurate measurements. This approach of molecular engineering is broadly applicable to diverse molecular species and states, including those with complex nuclei and those that are compatible with state-of-the-art cooling and trapping techniques, thereby offering the potential to significantly improve experimental sensitivity to a wide range of New Physics while expanding the chemical design space for molecular quantum science.

physics.atom-ph↗

arXiv2025

Prospects for measuring the electron's electric dipole moment with polyatomic molecules in an optical lattice

We present the conceptual design of an experiment to measure the electron's electric dipole moment (eEDM) using $^{138}$BaOH molecules in an optical lattice. The BaOH molecule is laser-coolable and highly sensitive to the eEDM, making it an attractive candidate for such a precision measurement, and capturing it in an optical lattice offers potentially very long coherence times. We study possibilities and limitations of this approach, identify the most crucial limiting factors and ways to overcome them. The proposed apparatus can reach a statistical error of $10^{-30}\,e\,$cm by measuring spin precession on a total number of $5 \times 10^9$ molecules over a span of 120 days.

physics.atom-ph↗

arXiv2025

Rapid, Broadband, Optical Spectroscopy of Cold Radicals

Optical spectroscopy of molecular radicals is an important tool in physical chemistry, and is a prerequisite for many experiments which use molecules for quantum science and precision measurement. However, even the simplest molecules have complex spectra which can be very time consuming to measure. Here we present an approach which offers the ability to measure the optical spectra of cryogenically-cooled molecular radicals with much greater efficiency. By combining a supercontinuum laser with a cryogenic buffer gas molecular source and a commercial optical spectrometer, we realize 15 nm of simultaneous bandwidth with 0.56 pm $(\approx 0.5$ GHz) resolution and high sensitivity. As a demonstration we measure and assign hundreds of lines and dozens of molecular constants from 15 bands in the $B^2Σ^+-X^2Σ^+$ system of CaF, including a low-abundance isotopologue, in a few hours. The setup is robust, simple, and should enable spectroscopy of molecular radicals with much higher throughput.

physics.chem-ph↗

arXiv2025

A Molecular Beam Study of the (0,0) A2Π<- X2Σ+ Band of CaF Isotopologues

This study presents an experimental determination of spectroscopic parameters for the less-abundant isotopologues $^{42}$CaF and $^{44}$CaF, alongside $^{40}$CaF, using high-resolution laser-induced fluorescence spectroscopy in a skimmed free jet expansion. We recorded spectra near the natural linewidth limit and derived spectroscopic constants for both the $X^2Σ^+$ and $A^2Π$ electronic states, including the fine and $^{19}$F magnetic hyperfine parameters. We also estimated the isotope amount ratio $r(^{44}\mathrm{Ca}/^{40}\mathrm{Ca})$, demonstrating the potential use of optical spectroscopy for calcium isotope analysis.

physics.chem-ph↗

arXiv2024

Searching for axion forces with spin precession in atoms and molecules

We propose to use atoms and molecules as quantum sensors of axion-mediated monopole-dipole forces. We show that electron spin precession experiments using atomic and molecular beams are well-suited for axion searches thanks to the presence of co-magnetometer states and single-shot temporal resolution. Experimental strategies to detect axion gradients from localised sources and the earth are presented, taking ACME III as a prototype example. Other possibilities including atomic beams, and laser-cooled atoms and molecules are discussed.

hep-ph↗

arXiv2024

Relativistic Exact Two-Component Coupled-Cluster Study of Molecular Sensitivity Factors for Nuclear Schiff Moments

Relativistic exact two-component coupled-cluster calculations of molecular sensitivity factors for nuclear Schiff moments (NSMs) are reported. We focus on molecules containing heavy nuclei, especially octupole-deformed nuclei. Analytic relativistic coupled-cluster gradient techniques are used and serve as useful tools for identifying candidate molecules that sensitively probe for physics beyond the Standard Model in the hadronic sector. Notably, these tools enable straightforward ``black-box'' calculations. Two competing chemical mechanisms that contribute to the NSM are analyzed, illuminating the physics of ligand effects on NSM sensitivity factors.

physics.atom-ph↗

arXiv2023

$\mathcal{CP}$-violation sensitivity of closed-shell radium-containing polyatomic molecular ions

Closed-shell atoms and molecules such as Hg or TlF provide some of the best low-energy tests of hadronic $\mathcal{CP}$-violation which is considered to be a necessary ingredient to explain the observed excess of matter over antimatter in our universe. $\mathcal{CP}$-violation is, however, expected to be strongly enhanced in octupole deformed nuclei such as $^{225}$Ra. Recently, closed-shell radium-containing symmetric-top molecular ions were cooled sympathetically in a Coulomb crystal [M. Fan et al., Phys. Rev. Lett. 126, 023002 (2021)] and shown to be well-suited for precision spectroscopy in the search for fundamental physics [P. Yu and N. R. Hutzler, Phys. Rev. Lett. 126, 023003 (2021)]. In closed-shell molecules hadronic $\mathcal{CP}$-violation contributes to a net electric dipole moment (EDM) that violates parity and time-reversal symmetry ($\mathcal{P,T}$), which is the target of measurements. To interpret experiments, it is indispensable to know the electronic structure enhancement parameters for the various sources of $\mathcal{P,T}$-violation which contribute to the net $\mathcal{P,T}$-odd EDM. In this paper we employ relativistic Hartree--Fock and density functional theory calculations to determine relevant parameters for interpretation of possible EDM measurements in RaOCH$_3^+$, RaSH$^+$, RaCH$_3^+$, RaCN$^+$, and RaNC$^+$ and perform accurate relativistic coupled cluster calculations of the Schiff moment enhancement in RaSH$^+$ to gauge the quality of the density functional theory approach. Finally, we project to bounds on various fundamental $\mathcal{P,T}$-odd parameters that could be achievable from an experiment with RaOCH$_3^+$ in the near future and asses the complementarity of this experiment to experiments with Hg and TlF.

physics.atom-ph↗

arXiv2023

Engineering field-insensitive molecular clock transitions for symmetry violation searches

Molecules are a powerful platform to probe fundamental symmetry violations beyond the Standard Model, as they offer both large amplification factors and robustness against systematic errors. As experimental sensitivities improve, it is important to develop new methods to suppress sensitivity to external electromagnetic fields, as limits on the ability to control these fields are a major experimental concern. Here we show that sensitivity to both external magnetic and electric fields can be simultaneously suppressed using engineered radio frequency, microwave, or two-photon transitions that maintain large amplification of CP-violating effects. By performing a clock measurement on these transitions, CP-violating observables including the electron electric dipole moment, nuclear Schiff moment, and magnetic quadrupole moment can be measured with suppression of external field sensitivity of $\gtrsim$100 generically, and even more in many cases. Furthermore, the method is compatible with traditional Ramsey measurements, offers internal co-magnetometry, and is useful for systems with large angular momentum commonly present in molecular searches for nuclear CP-violation.

physics.atom-ph↗

arXiv2023

Quantum-Enhanced Metrology for Molecular Symmetry Violation using Decoherence-Free Subspaces

We propose a method to measure time-reversal symmetry violation in molecules that overcomes the standard quantum limit while leveraging decoherence-free subspaces to mitigate sensitivity to classical noise. The protocol does not require an external electric field, and the entangled states have no first-order sensitivity to static electromagnetic fields as they involve superpositions with zero average lab-frame projection of spins and dipoles. This protocol can be applied with trapped neutral or ionic species, and can be implemented using methods which have been demonstrated experimentally.

physics.atom-ph↗

arXiv2023

Sympathetic cooling and slowing of molecules with Rydberg atoms

We propose to sympathetically slow and cool polar molecules in a cold, low-density beam using laser-cooled Rydberg atoms. The elastic collision cross sections between molecules and Rydberg atoms are large enough to efficiently thermalize the molecules even in a low density environment. Molecules traveling at 100 m/s can be stopped in under 30 collisions with little inelastic loss. Our method does not require photon scattering from the molecules and can be generically applied to complex species for applications in precision measurement, quantum information science, and controlled chemistry.

physics.atom-ph↗

arXiv2023

Intensity-borrowing mechanisms pertinent to laser cooling of linear polyatomic molecules

A study of the intensity-borrowing mechanisms important to optical cycling transitions in laser-coolable polyatomic molecules arising from non-adiabatic coupling, contributions beyond the Franck-Condon approximation, and Fermi resonances is reported. It has been shown to be necessary to include non-adiabatic coupling to obtain computational accuracy that is sufficient to be useful for laser cooling of molecules. The predicted vibronic branching ratios using perturbation theory based on the non-adiabatic mechanisms have been demonstrated to agree well with those obtained from variational discrete variable representation calculations for representative molecules including CaOH, SrOH, and YbOH. The electron-correlation and basis-set effects on the calculated transition properties, including the vibronic coupling constants, the spin-orbit coupling matrix elements, and the transition dipole moments, and on the calculated branching ratios have been thoroughly studied. The vibronic branching ratios predicted using the present methodologies demonstrate that RaOH is a promising radioactive molecule candidate for laser cooling.

physics.chem-ph↗

arXiv2023

Optical cycling in polyatomic molecules with complex hyperfine structure

We have developed and demonstrated a scheme to achieve rotationally-closed photon cycling in polyatomic molecules with complex hyperfine structure and sensitivity to hadronic symmetry violation, specifically $^{171}$YbOH and $^{173}$YbOH. We calculate rotational branching ratios for spontaneous decay and identify repumping schemes which use electro-optical modulators (EOMs) to address the hyperfine structure. We demonstrate our scheme by cycling photons in a molecular beam and verify that we have achieved rotationally-closed cycling by measuring optical pumping into unaddressed vibrational states. Our work makes progress along the path toward utilizing photon cycling for state preparation, readout, and laser cooling in precision measurements of polyatomic molecules with complex hyperfine structure.

physics.atom-ph↗

arXiv2023

Direct measurement of high-lying vibrational repumping transitions for molecular laser cooling

Molecular laser cooling and trapping requires addressing all spontaneous decays to excited vibrational states that occur at the $\gtrsim 10^{-4} - 10^{-5}$ level, which is accomplished by driving repumping transitions out of these states. However, the transitions must first be identified spectroscopically at high-resolution. A typical approach is to prepare molecules in excited vibrational states via optical cycling and pumping, which requires multiple high-power lasers. Here, we demonstrate a general method to perform this spectroscopy without the need for optical cycling. We produce molecules in excited vibrational states by using optically-driven chemical reactions in a cryogenic buffer gas cell, and implement frequency-modulated absorption to perform direct, sensitive, high-resolution spectroscopy. We demonstrate this technique by measuring the spectrum of the $\tilde{A}^2Π_{1/2}(1,0,0)-\tilde{X}^2Σ^+(3,0,0)$ band in $^{174}$YbOH. We identify the specific vibrational repump transitions needed for photon cycling, and combine our data with previous measurements of the $\tilde{A}^2Π_{1/2}(1,0,0)-\tilde{X}^2Σ^+(0,0,0)$ band to determine all of the relevant spectral constants of the $\tilde{X}^2Σ^+(3,0,0)$ state. This technique achieves high signal-to-noise, can be further improved to measure increasingly high-lying vibrational states, and is applicable to other molecular species favorable for laser cooling.

physics.atom-ph↗

arXiv2023

Non-resonant cavity for intensity buildup of multiple lasers

A non-resonant cavity to build up laser intensity is modeled, developed and tested. It can be used for overlapping multiple lasers of different wavelengths, increasing their intensities by over an order of magnitude while maintaining good uniformity. It is simple to set up, has flexible optical characteristics, and is robust against perturbations. The intensity buildup requires no resonances, and the wavelength dependence of the performance is limited only by the mirror coatings. The cavity can be used in applications requiring a spatially-constrained intensity buildup, for example in atomic and molecular traps.

physics.optics↗

arXiv2023

Opportunities for Fundamental Physics Research with Radioactive Molecules

Molecules containing short-lived, radioactive nuclei are uniquely positioned to enable a wide range of scientific discoveries in the areas of fundamental symmetries, astrophysics, nuclear structure, and chemistry. Recent advances in the ability to create, cool, and control complex molecules down to the quantum level, along with recent and upcoming advances in radioactive species production at several facilities around the world, create a compelling opportunity to coordinate and combine these efforts to bring precision measurement and control to molecules containing extreme nuclei. In this manuscript, we review the scientific case for studying radioactive molecules, discuss recent atomic, molecular, nuclear, astrophysical, and chemical advances which provide the foundation for their study, describe the facilities where these species are and will be produced, and provide an outlook for the future of this nascent field.

nucl-ex↗

arXiv2023

Quantum Control of Trapped Polyatomic Molecules for eEDM Searches

Ultracold polyatomic molecules are promising candidates for experiments in quantum science, quantum sensing, ultracold chemistry, and precision measurements of physics beyond the Standard Model. A key, yet unrealized, requirement of these experiments is the ability to achieve full quantum control over the complex internal structure of the molecules. Here, we establish coherent control of individual quantum states in a polyatomic molecule, calcium monohydroxide (CaOH), and use these techniques to demonstrate a method for searching for the electron electric dipole moment (eEDM). Optically trapped, ultracold CaOH molecules are prepared in a single quantum state, polarized in an electric field, and coherently transferred into an eEDM sensitive state where an electron spin precession measurement is performed. To extend the coherence time of the measurement, we utilize eEDM sensitive states with tunable, near-zero magnetic field sensitivity. The spin precession coherence time is limited by AC Stark shifts and uncontrolled magnetic fields. These results establish a path for eEDM searches with trapped polyatomic molecules, towards orders-of-magnitude improved experimental sensitivity to time-reversal-violating physics.

physics.atom-ph↗