Development of Frequency Comb Velocity-Modulation Spectroscopy, Spectroscopy of Hafnium Fluoride Ion (+) and the JILA eEDM Experiment

Abstract

Broad bandwidth, precision spectroscopy of the molecular ions of interest to the JILA electron electric dipole moment experiment, HfF⁺ and ThF⁺, is necessary due to the limited amount of spectroscopic information available and the large theoretical uncertainties in the energy level structure (thousands of wavenumbers). This thesis covers the development of a novel spectroscopic technique, frequency comb velocity-modulation spectroscopy, that provides high resolution, broad spectral bandwidth, ion discrimination and high sensitivity simultaneously. Frequency comb velocity-modulation spectroscopy as well as single-frequency velocity-modulation spectroscopy have been used to identify five rotational bands of HfF⁺. This work discusses the first spectroscopic information for HfF⁺ which came from our measurement of the ¹Π₁ – ¹Σ+ (0,0) band recorded with single-frequency velocitymodulation spectroscopy with a sensitivity of 3x10^-7 Hz^-1/2. The development of frequency comb velocity-modulation spectroscopy allowed us to cover a thousand wavenumbers of spectral bandwidth and to identify an additional four HfF ⁺ bands. The achieved sensitivity for frequency-comb velocity-modulation spectroscopy was 4x10^-8 Hz^-1/2 (spectral element) ^-1/2 with 1500 simultaneous detection channels spanning 150 cm ^-1 of bandwidth. For a 30 minute acquisition time using 30 interleaved images to densely sample the whole spectrum, this corresponded to a 3x10 ^-7 single-pass fractional absorption sensitivity for each of the 45,000 measurement channels. The spectroscopic information from all five HfF ⁺ rotational bands is presented and molecular constants for the ¹Σ+, ³Π₁, and ¹Π₁ states were extracted.