Quantum Beat Photoelectron Imaging Spectroscopy of Xe in the VUV

TL;DR

This paper demonstrates a novel quantum beat photoelectron imaging spectroscopy technique on xenon, revealing hyperfine state splittings and isotope-specific information through angle- and time-resolved photoelectron images.

Contribution

It introduces a quantum beat imaging modality that extracts hyperfine and isotope information from photoelectron images using Fourier analysis, advancing time-resolved spectroscopy methods.

Findings

Measured hyperfine state splittings in Xe with high precision.

Developed a Fourier analysis method for extracting isotope-specific photoelectron images.

Showed utility of phase and frequency domain analysis in photoelectron imaging.

Abstract

Time-resolved pump-probe measurements of Xe, pumped at 133~nm and probed at 266~nm, are presented. The pump pulse prepared a long-lived hyperfine wavepacket, in the Xe $5p^5(^2P^{\circ}_{1/2})6s~^2[1/2]^{\circ}_1$ manifold ($E=$77185 cm$^{-1}=$9.57 eV). The wavepacket was monitored via single-photon ionization, and photoelectron images measured. The images provide angle- and time-resolved data which, when obtained over a large time-window (900~ps), constitute a precision quantum beat spectroscopy measurement of the hyperfine state splittings. Additionally, analysis of the full photoelectron image stack provides a quantum beat imaging modality, in which the Fourier components of the photoelectron images correlated with specific beat components can be obtained. This may also permit the extraction of isotope-resolved photoelectron images in the frequency domain, in cases where nuclear spins (hence beat components) can be uniquely assigned to specific isotopes (as herein), and also provides phase information. The information content of both raw, and inverted, image stacks is investigated, suggesting the utility of the Fourier analysis methodology in cases where images cannot be inverted.