Direct Measurement of the Forbidden $2^3{S}_1\to 3^3{S}_1$ Atomic Transition in Helium

Abstract

We present the detection of the highly forbidden $2^3{S}_1\to 3^3{S}_1$ atomic transition in helium, the weakest transition observed in any neutral atom. Our measurements of the transition frequency, upper state lifetime, and transition strength agree well with published theoretical values, and can lead to tests of both QED contributions and different QED frameworks. To measure such a weak transition, we developed two methods using ultracold metastable ($2^3{S}_1$) helium atoms: low background direct detection of excited then decayed atoms for sensitive measurement of the transition frequency and lifetime; and a pulsed atom laser heating measurement for determining the transition strength. These methods could possibly be applied to other atoms, providing new tools in the search for ultra-weak transitions and precision metrology.

18 pages, 13 figures, 3 tables

References in corpus (6)

• Species-specific optical lattices
• Extreme ultraviolet frequency comb metrology
• Frequency metrology of helium around 1083 nm and determination of the nuclear charge radius
• High-precision spectroscopy of the forbidden 2 3S1 - 2 1P1 transition in quantum degenerate metastable helium
• QED calculation of transition probabilities in two-electron ions
• QED and relativistic nuclear recoil corrections to the 413 nm tune-out wavelength for the $2{}^3{S}_1$ state of helium

Cited by in corpus (5)

• Precision calculation of hyperfine structure and the Zemach radii of ${}^{6,7}$Li${}^{+}$ ions
• Measurement of a helium tune-out frequency: an independent test of quantum electrodynamics
• Proposal for suppressing ac Stark shift in the He($2{}^3{S}_1\to 3{}^3{S}_1$) two-photon transition using magic wavelengths
• Pulse Breathing Dynamics in a Mode-Locked Laser measured via SHG autocorrelation
• Frequency measurements of transitions from the $2^3{P}_2$ state to the $5^1{D}_2$, $5^3{S}_1$, and $5^{3}D$ states in ultracold helium