Visible and ultraviolet laser spectroscopy of ThF

Abstract

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 ∆ 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 Ω = 3/2 [32.85] intermediate state. In addition, we propose a method to increase the aforementioned efficiency to ∼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.

Long-range model of vibrational autoionization in core-nonpenetrating Rydberg states of NO

“…Sev- eral experiments in precision measurement 9,37 and cold chemistry 6,38 require molecular ions in a single quantum state, but typical methods of ion production (e.g., discharge, laser ablation) are violent and produce ions in numerous quantum states. In contrast, autoionization of Rydberg states has been used in a few previous experiments 8,9 to generate molecular ions in only a few quantum states, greatly increasing the yield of the desired state and reducing the complexity of subsequent state preparation steps. The calculated rotational state distributions presented here demonstrate that greater selectivity in the generation of single quantum state ions is possible by careful selection of high-Rydberg states as the precursor to autoionization.…”

“…However, in recent applications, this approach has only succeeded in producing molecular ions distributed over at least three final rotational states. 8,9 Indeed, earlier work demonstrated that rotational quantum number changes as large as four quanta are possible in the autoionization of certain Rydberg series, 10,11 upending the simple picture of the Rydberg electron being released without perturbation of the ion-core.…”

Spectroscopy on the eEDM-sensitive states of ThF$^+$

“…The latter keeps all the benefits of using molecular ions in an ion trap, and it also boasts a larger effective electric field and longer coherence times than the former [18][19][20][21]26], both of which promise a direct increase in the eEDM sensitivity. Previous spectroscopic work [26][27][28][29] shows that we can use similar experimental techniques across both molecular species, including multi-state detection [25,30]. Hence, the molecule switch presents no new immediate experimental complexity, and promises higher eEDM sensitivity.…”

“…Borrowing wisdom and experimental techniques from similar spectroscopic work performed on HfF + [31][32][33][34], ThF [27], and ThF + [26], we (i) perform spectroscopy on the eEDM-sensitive state in ThF + , X 3 ∆ 1 , (Section II) to extract spectroscopic constants of concern, and discuss theoretical calculations of aforementioned spectroscopic constants; and (ii) study the lifetime of the first vibrational excited state in ThF + (Section III) and its implications on the expected coherence time of X 3 ∆ 1 .…”

Electronic structure of NdO via slow photoelectron velocity-map imaging spectroscopy of NdO¯

“…Spectroscopy of the atomic lanthanides is well characterized, 19 but the spectroscopy of the oxides is very much a work in progress. 20,21 SmO, NdO, and their cations have many low-lying electronic states due to their partially filled f-shells and are challenging to explore. Electronic states of NdO + with term energies of up to ~5,000 cm -1 have been determined using pulsed-field ionization zero electron kinetic energy (PFI-ZEKE) spectroscopy.…”