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arXiv:2501.02999 · Physical Review A

Combining laser cooling and Zeeman deceleration for precision spectroscopy in supersonic beams

Gloria Clausen, Laura Gabriel, Josef A. Agner, Hansjürg Schmutz, Tobias Thiele, Andreas J. Wallraff, Frédéric Merkt

Published Oct 3, 2024• 2 citations
arXivHTMLPDF

Abstract

Precision spectroscopic measurements in atoms and molecules play an increasingly important role in chemistry and physics, e.g., to characterize structure and dynamics at long timescales, to determine physical constants, or to search for physics beyond the standard model of particle physics. In this paper, we demonstrate the combination of Zeeman deceleration and transverse laser cooling to generate slow (mean velocity of 175 m/s) and transversely ultracold (${T}_{\ensuremath{\perp}}\ensuremath{\approx}135\phantom{\rule{0.28em}{0ex}}\textmu{}\mathrm{K}$) supersonic beams of metastable $(1s)(2s)\phantom{\rule{0.16em}{0ex}}^{3}S_{1}$ He (${\mathrm{He}}^{*}$) for precision spectroscopy. The curved-wavefront laser-cooling approach is used to achieve large capture velocities and high ${\mathrm{He}}^{*}$ number densities. The beam properties are characterized by imaging, time-of-flight, and high-resolution spectroscopic methods, and the factors limiting the Doppler widths in single-photon spectroscopic measurements of the $(1s)(40p)\phantom{\rule{0.16em}{0ex}}^{3}P_{J}\phantom{\rule{0.16em}{0ex}}\ensuremath{\leftarrow}(1s)(2s)\phantom{\rule{0.16em}{0ex}}^{3}S_{1}$ transition at UV frequencies around $1.15\ifmmode\times\else\texttimes\fi{}{10}^{15}$ Hz are analyzed. In particular, the use of skimmers to geometrically confine the beam in the transverse directions is examined and shown to not always lead to a reduction of the Doppler width. Linewidths as narrow as 5 MHz could be obtained, enabling the determination of line centers with a precision of $\mathrm{\ensuremath{\Delta}}\ensuremath{\nu}/\ensuremath{\nu}$ of $4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}$ limited by the signal-to-noise ratio. Numerical particle-trajectory simulations are used to interpret the experimental observations and validate the conclusions.

DOI
10.1103/physreva.110.042802

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A production of low velocity and monoenergetic atomic beams would increase the resolution in spectroscopic studies and many other experiments in atomic physics. Laser Cooling uses the radiation pressure to decelerate and cool atoms. The effusing from a glow discharge metastable argon atomic beam is affected by a counterpropagating laser light tuned to the cycling transition in argon. The Zeeman shift caused by a spatially varying magnetic field compensates for the changing Doppler shift that takes the atoms out of resonance as they decelerated. Deceleration and velocity bunching of atoms to a final velocity that depends on the detuning of the laser relative to a frequency of the transition have been observed. Time-of-Flight (TOF) spectroscopy is used to examine the velocity distribution of the cooled atomic beam. These TOF studies of the laser cooled atomic beam demonstrate the utility of laser deceleration for atomic-beam "velocity selection".