Visible and Ultraviolet Laser Spectroscopy of ThF

The molecular ion ThF$^+$ is the species to be used in the next generation of search for the electron's Electric Dipole Moment (eEDM) at JILA. The measurement requires creating molecular ions in the eEDM sensitive state, the rovibronic ground state $^3\Delta_1$, $v^+=0$, $J^+=1$. Survey spectroscopy of neutral ThF is required to identify an appropriate intermediate state for a Resonance Enhanced Multi-Photon Ionization (REMPI) scheme that will create ions in the required state. We perform broadband survey spectroscopy (from 13000 to 44000~cm$^{-1}$) of ThF using both Laser Induced Fluorescence (LIF) and $1+1'$ REMPI spectroscopy. We observe and assign 345 previously unreported vibronic bands of ThF. We demonstrate 30\% efficiency in the production of ThF$^+$ ions in the eEDM sensitive state using the $\Omega = 3/2$ [32.85] intermediate state. In addition, we propose a method to increase the aforementioned efficiency to $\sim$100\% by using vibrational autoionization via core-nonpenetrating Rydberg states, and discuss theoretical and experimental challenges. Finally, we also report 83 vibronic bands of an impurity species, ThO.Comment: 49 pages, 7 figure

Broadband velocity modulation spectroscopy of HfF^+: towards a measurement of the electron electric dipole moment

Precision spectroscopy of trapped HfF^+ will be used in a search for the permanent electric dipole moment of the electron (eEDM). While this dipole moment has yet to be observed, various extensions to the standard model of particle physics (such as supersymmetry) predict values that are close to the current limit. We present extensive survey spectroscopy of 19 bands covering nearly 5000 cm^(-1) using both frequency-comb and single-frequency laser velocity-modulation spectroscopy. We obtain high-precision rovibrational constants for eight electronic states including those that will be necessary for state preparation and readout in an actual eEDM experiment.Comment: 13 pages, 7 figures, 3 table

Experimental Constraint on Axionlike Particles over Seven Orders of Magnitude in Mass

We use our recent electric dipole moment (EDM) measurement data to constrain the possibility that the HfF+ EDM oscillates in time due to interactions with candidate dark matter axionlike particles (ALPs). We employ a Bayesian analysis method which accounts for both the look-elsewhere effect and the uncertainties associated with stochastic density fluctuations in the ALP field. We find no evidence of an oscillating EDM over a range spanning from 27 nHz to 400 mHz, and we use this result to constrain the ALP-gluon coupling over the mass range 10-22-10-15 eV. This is the first laboratory constraint on the ALP-gluon coupling in the 10-17-10-15 eV range, and the first laboratory constraint to properly account for the stochastic nature of the ALP field

BROADBAND VELOCITY MODULATION SPECTROSCOPY OF MOLECULAR IONS FOR USE IN THE JILA ELECTRON EDM EXPERIMENT

Author Institution: JILA, National Institute of Standards and Technology and University of Colorado Department of Physics, University of Colorado, Boulder, Colorado 80309-0440, USAThe JILA electron electric dipole moment (eEDM) experiment will use a low-lying, metastable $^3\Delta_1$ state in trapped molecular ions of HfF$^+$ or ThF$^+$. Prior to this work, the low-lying states of these molecules had been investigated by PFI-ZEKE spectroscopy. However, there were no detailed studies of the electronic structure. The recently developed technique of frequency comb velocity modulation spectroscopy (VMS) provides broad-bandwidth, high-resolution, ion-sensitive spectroscopy, allowing the acquisition of 150 cm$^{-1}$ of continuous spectra in 30 minutes over 1500 simultaneous channels. By supplementing this technique with cw-laser VMS, we have investigated the electronic structure of HfF$^+$ in the frequency range of 9950 to 14600 cm$^{-1}$, accurately fitting and assigning 16 rovibronic transitions involving 8 different electronic states including the $X^1\Sigma^+$ and $a^3\Delta_1$ states. In addition, an observed $^3\Pi_{0+}$ state with coupling to both the $X$ and $a$ states has been used in the actual eEDM experiment to coherently transfer population from the rovibronic ground state of HfF$^+$ to the eEDM science state. Furthermore, we report on current efforts of applying frequency comb VMS at 700 - 900 nm to the study of ThF$^+$, which has a lower energy $^3\Delta_1$ state and a greater effective electric field, and will provide increased sensitivity for a measurement of the eEDM

PROGRESS OF THE JILA ELECTRON EDM EXPERIMENT

Author Institution: JILA, National Institute of Standards and Technology and University of Colorado Department of Physics, University of Colorado, Boulder, Colorado 80309-0440, USAMolecules can be advantageous for the search for the electron electric dipole moment (eEDM) due to the large effective electric field experienced by a bound, unpaired electron. Furthermore, the closely-spaced states of opposite parity make the molecules easy to polarize in the lab frame. The JILA eEDM experiment currently uses HfF$^+$ molecules in an ion trap to achieve long coherence times to reduce systematics. When an electric field is applied the eEDM signal is proportional to the shift in energy splitting between two Zeeman levels in a low-lying, metastable $^3\Delta_1$ state. We have previously shown efficient preparation of trapped HfF$^+$ molecules in the rovibronic ground state, $X^1\Sigma^+(v=0,J=0)$. Here, we demonstrate coherent transfer of population from the ground state to the $a^3\Delta_1(v=0, J=1)$ state through an intermediate $^3\Pi_{0+}$ state and efficient state read-out using photodissociation. In addition, we have begun to take spectroscopy data of the hyperfine and Zeeman structure of the eEDM science state in the presence of a rotating bias electric field and a magnetic field