The search for a permanent electron electric dipole moment (eEDM) serves as a test of fundamental symmetry violations and of physics beyond the Standard Model. Trapped molecular ions in the 3Δ1 metastable electronic state are suitable candidates for an eEDM search due to their large effective electric fields and long electron spin coherence times. This thesis presents the quantum state manipulation and coherent spectroscopy of trapped HfF+ molecular ions in rotating bias fields for an eEDM search. The quantum state manipulation, which involves preparation of a large fraction of molecular ions in a single desired quantum state as well as rotational-state-resolved detection, is complicated by the lack of HfF+ spectroscopic information prior to the start of this thesis. We performed state preparation by first state-selectively autoionizing neutral HfF such that 35% of the HfF+ are formed in a single rovibrational level of the electronic ground state 1Σ+, and then transferring those ions into the desired Stark levels of a single hyperfine-rovibrational manifold of the 3Δ1 state. Rotational-state-resolved detection is accomplished by both laser-induced fluorescence and resonance-enhanced multi-photon photodissociation, where the latter is preferred as the state detection method of choice because its efficiency is two orders of magnitude higher compared to fluorescence. With the quantum state manipulation techniques developed, we performed Ramsey spectroscopy of the trapped HfF+ ions in the presence of rotating bias electric and magnetic fields, demonstrating electron spin coherence times as long as 150 ms. Finally, we present a preliminary measurement of the eEDM at the |de| < 10-25 e cm level.The search for a permanent electron electric dipole moment (eEDM) serves as a test of fundamental symmetry violations and of physics beyond the Standard Model. Trapped molecular ions in the 3Δ1 metastable electronic state are suitable candidates for an eEDM search due to their large effective electric fields and long electron spin coherence times. This thesis presents the quantum state manipulation and coherent spectroscopy of trapped HfF+ molecular ions in rotating bias fields for an eEDM search. The quantum state manipulation, which involves preparation of a large fraction of molecular ions in a single desired quantum state as well as rotational-state-resolved detection, is complicated by the lack of HfF+ spectroscopic information prior to the start of this thesis. We performed state preparation by first state-selectively autoionizing neutral HfF such that 35% of the HfF+ are formed in a single rovibrational level of the electronic ground state 1Σ+, and then transferring those ions into the desired Stark levels of a single hyperfine-rovibrational manifold of the 3Δ1 state. Rotational-state-resolved detection is accomplished by both laser-induced fluorescence and resonance-enhanced multi-photon photodissociation, where the latter is preferred as the state detection method of choice because its efficiency is two orders of magnitude higher compared to fluorescence. With the quantum state manipulation techniques developed, we performed Ramsey spectroscopy of the trapped HfF+ ions in the presence of rotating bias electric and magnetic fields, demonstrating electron spin coherence times as long as 150 ms. Finally, we present a preliminary measurement of the eEDM at the |de| < 10-25 e cm level.

Jan 1, 20132 citations

Trapping, Cooling, and Photodissociation Analysis of State-Selected H2+ Ions Produced by ( 3+1 ) Multiphoton Ionization

Julian Schmidt, Thomas Louvradoux, Johannes Heinrich +4 more

We report on the production of cold, state-selected ${\mathrm{H}}_{2}^{+}$ molecular ions in a linear rf trap. The ions are produced by ( $3+1$ ) resonance-enhanced multiphoton ionization (REMPI) of ${\mathrm{H}}_{2}$ , and sympathetically cooled by laser-cooled ${\mathrm{Be}}^{+}$ ions. After demonstrating and characterizing the REMPI process, we use photodissociation by a deep UV laser at 213 nm to verify the high vibrational purity of the produced ${\mathrm{H}}_{2}^{+}$ ion samples. Moreover, the large difference between the photodissociation efficiencies of ions created in the $v=0$ and $v=1$ levels provides a way to detect a $v=0\ensuremath{\rightarrow}1$ transition. These results pave the way towards high-resolution vibrational spectroscopy of ${\mathrm{H}}_{2}^{+}$ for fundamental metrology applications.We report on the production of cold, state-selected ${\mathrm{H}}_{2}^{+}$ molecular ions in a linear rf trap. The ions are produced by ($3+1$) resonance-enhanced multiphoton ionization (REMPI) of ${\mathrm{H}}_{2}$, and sympathetically cooled by laser-cooled ${\mathrm{Be}}^{+}$ ions. After demonstrating and characterizing the REMPI process, we use photodissociation by a deep UV laser at 213 nm to verify the high vibrational purity of the produced ${\mathrm{H}}_{2}^{+}$ ion samples. Moreover, the large difference between the photodissociation efficiencies of ions created in the $v=0$ and $v=1$ levels provides a way to detect a $v=0\ensuremath{\rightarrow}1$ transition. These results pave the way towards high-resolution vibrational spectroscopy of ${\mathrm{H}}_{2}^{+}$ for fundamental metrology applications.

arXiv:2008.11407Physical Review AppliedAug 19, 202031 citations

Spectroscopy of Trapped Negative Ions

Daniel J. Larson, R.M. Jopson

Springer series in optical sciences/SPringer series in optical sciencesJan 1, 19812 citations

Selective Excitation by Photodissociation of Molecules

C. R. Gould

Quantum ElectronicsJan 1, 19640 citations

High-efficiency quantum-state detection of ThF + with resonance-enhanced multiphoton asymmetric dissociation

Kia Boon Ng, Sun Yool Park, Anzhou Wang +7 more

Efficient quantum-state detection is crucial for many precision control experiments, such as the ongoing effort to probe the electron's electric dipole moment using trapped molecular ThF + 232 ions at JILA. While quantum-state detection through state-selective photodissociation has been successfully implemented on this molecule, progress has been hindered by low dissociation efficiency. In this work, we perform spectroscopy on the molecule to identify excited states that facilitate more efficient photodissociation. For the most favorable transition, we achieve a dissociation efficiency of 57(14)% with quantum-state selectivity. Additionally, we discuss several state detection protocols that leverage favorable excited states that will facilitate simultaneous readout of all EDM relevant states, allowing further improvement of overall statistics.Efficient quantum-state detection is crucial for many precision control experiments, such as the ongoing effort to probe the electron's electric dipole moment using trapped molecular ThF + 232 ions at JILA. While quantum-state detection through state-selective photodissociation has been successfully implemented on this molecule, progress has been hindered by low dissociation efficiency. In this work, we perform spectroscopy on the molecule to identify excited states that facilitate more efficient photodissociation. For the most favorable transition, we achieve a dissociation efficiency of 57(14)% with quantum-state selectivity. Additionally, we discuss several state detection protocols that leverage favorable excited states that will facilitate simultaneous readout of all EDM relevant states, allowing further improvement of overall statistics.

arXiv:2508.04949Physical Review ANov 6, 20252 citations

We report on the production of cold, state-selected

{\mathrm{H}}_{2}^{+}

molecular ions in a linear rf trap. The ions are produced by (

3+1

) resonance-enhanced multiphoton ionization (REMPI) of

{\mathrm{H}}_{2}

, and sympathetically cooled by laser-cooled

{\mathrm{Be}}^{+}

ions. After demonstrating and characterizing the REMPI process, we use photodissociation by a deep UV laser at 213 nm to verify the high vibrational purity of the produced

{\mathrm{H}}_{2}^{+}

ion samples. Moreover, the large difference between the photodissociation efficiencies of ions created in the

v=0

and

v=1

levels provides a way to detect a $v=0\ensuremath{\rightarrow}1$ transition. These results pave the way towards high-resolution vibrational spectroscopy of

{\mathrm{H}}_{2}^{+}

for fundamental metrology applications.