Prospects for precision measurements of atomic helium using direct frequency comb spectroscopy

Abstract

We analyze several possibilities for precisely measuring electronic transitions in atomic helium by the direct use of phase-stabilized femtosecond frequency combs. Because the comb is self-calibrating and can be shifted into the ultraviolet spectral region via harmonic generation, it offers the prospect of greatly improved accuracy for UV and far-UV transitions. To take advantage of this accuracy an ultracold helium sample is needed. For measurements of the triplet spectrum a magneto-optical trap (MOT) can be used to cool and trap metastable 2^3S state atoms. We analyze schemes for measuring the two-photon $2^{3}S\to 4^{3}S$ interval, and for resonant two-photon excitation to high Rydberg states, $2^{3}S\to 3^{3}P\to n^{3}S,D$. We also analyze experiments on the singlet-state spectrum. To accomplish this we propose schemes for producing and trapping ultracold helium in the 1^1S or 2^1S state via intercombination transitions. A particularly intriguing scenario is the possibility of measuring the $1^{1}S\to 2^{1}S$ transition with extremely high accuracy by use of two-photon excitation in a magic wavelength trap that operates identically for both states. We predict a ``triple magic wavelength'' at 412 nm that could facilitate numerous experiments on trapped helium atoms, because here the polarizabilities of the 1^1S, 2^1S and 2^3S states are all similar, small, and positive.

Shortened slightly and reformatted for Eur. Phys. J. D

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Cited by in corpus (11)

• Direct Frequency Comb Spectroscopy in the Extreme Ultraviolet
• Cold and trapped metastable noble gases
• Frequency metrology in quantum degenerate helium: Direct measurement of the 2 3S1 - 2 1S0 transition
• Phase-matched extreme-ultraviolet frequency-comb generation
• Extreme Ultraviolet Radiation With Coherence Time Greater Than 1 s
• XUV Frequency Combs via Femtosecond Enhancement Cavities
• Magic wavelengths for the $2{}^{3}S\to 2{}^{1}S$ transition in helium
• Electric Dipole Polarizabilities of Hydrogen and Helium Isotopes
• Characterization of a vacuum ultraviolet light source at 118 nm
• Doppler-free intermodulated fluorescence spectroscopy of ${}^{4}He$ $2^{3}P-3^{1,3}D$ transitions at 588 nm with a one-watt compact laser system
• Angular correlations in two-photon spectroscopy of hydrogen