Frequency Metrology in Quantum Degenerate Helium: Direct Measurement of the 2
 3
 S
 1
 → 2
 1
 S
 0
 Transition

Rooij, Rob van; Borbely, Joseph Steven; Simonet, Juliette; Hoogerland, M. D.; Eikema, K.S.E.; Rozendaal, R. A.; Vassen, W.

doi:10.1126/science.1205163

Cited by 125 publications

(235 citation statements)

References 33 publications

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“…[7]. In short, we use a liquid-nitrogen cooled dc discharge to excite helium atoms into the metastable triplet state.…”

Section: Methodsmentioning

confidence: 99%

“…A small magnetic field is used to keep the atoms in the spin-polarized m = +1 state as atoms in the m = 0 state show fast Penning ionization [15]. m = −1 states are populated by rapid adiabatic passage using a magnetic field sweep [7,27]. In this way we can transfer nearly 100% of the atoms to m = −1.…”

Section: Methodsmentioning

confidence: 99%

“…These QED limited accuracies allow extraction of the squared nuclear charge radius difference with an accuracy that will be similar to values deduced from the muonic helium experiments if the experimental accuracy of the isotope shift is of similar or higher accuracy. Presently, for the 2 3 S 1 -2 1 S 0 transition, the accuracy is 2.4 kHz [7] while for the 2 3 S 1 -2 3 P transition the isotope shift accuracy is 3.2 kHz [8,9]. Surprisingly, a four standard deviation difference exists between the nuclear charge radius difference extracted from both measurements.…”

Section: Introductionmentioning

confidence: 91%

“…Aiming for a 0.1 kHz accuracy in the experimental transition frequency for both 4 He and 3 He several challenges have to be met. Looking at the error budget of our previous experiment [7] one major error source is the ac Stark shift as a result of the optical dipole trapping potential. This we will solve by working in a magic wavelength crossed dipole trap.…”

Section: Spectroscopymentioning

confidence: 99%

“…1.8 kHz accuracy [7]. The 2.3 kHz accuracy in the isotope shift, together with the 0.7 kHz theoretical accuracy in the point-nucleus isotope shift [6], has allowed a determination of the difference in the squared nuclear charge radius of 1.028 (11) fm 2 [6].…”

Section: Spectroscopymentioning

confidence: 99%

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Ultracold metastable helium: Ramsey fringes and atom interferometry

et al. 2016

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equation cannot be solved exactly. Level energies are therefore more difficult to calculate than for atomic hydrogen showing a more stringent test of atomic physics theory. Calculations of level energies and transition frequencies have pushed our understanding of atomic physics since the twenties of last century. A major breakthrough occurred in the nineties with the advent of variational calculations in a double basis set in correlated form for the electrons, adding relativistic and quantum electrodynamics (QED) terms in orders of the fine structure constant α and the reduced electron to helium mass ratio µ/M He [1, 2]. As nonrelativistic calculations can now be performed to virtually arbitrary precision, measurements of level energies nowadays are sensitive to QED and nuclear size effects. As these effects are strongest for S-states and small principle quantum number n, the n 1,3 S states are theoretically the most promising to test QED. In particular the n = 2 states are important for high-resolution spectroscopy as these also show long lifetimes, 7800 s for the 2 3 S 1 state and 20 ms for the 2 1 S 0 state (natural linewidth 8 Hz), while the 2 3 P state has, for an allowed electric dipole transition, a relatively long lifetime of 98 ns (natural linewidth 1.6 MHz). A helium level scheme is shown in Fig. 1.Transition frequencies in helium can nowadays be measured more accurately than calculated, where the theoretical limitation is in the calculation of high-order QED terms. This hampers extraction of the charge radius of the helium nucleus (the alpha-particle for 4 He and the helion for 3 He ) from transition frequencies with an accuracy that can compete with other experiments. However, in calculating transition isotope shifts between 4 He and 3 He, QED terms cancel to a large extent, allowing very accurate extraction of the difference in the (squared) nuclear charge radii of the alpha-particle and the helion. This is particularly interesting in relation to the proton size puzzle [3][4][5]. To help solving Abstract We report on interference studies in the internal and external degrees of freedom of metastable triplet helium atoms trapped near quantum degeneracy in a 1.5 µm optical dipole trap. Applying a single π/2 rf pulse we demonstrate that 50% of the atoms initially in the m = +1 state can be transferred to the magnetic field insensitive m = 0 state. Two π/2 pulses with varying time delay allow a Ramsey-type measurement of the Zeeman shift for a high precision measurement of the 2 3 S 1 -2 1 S 0 transition frequency. We show that this method also allows strong suppression of mean-field effects on the measurement of the Zeeman shift, which is necessary to reach the accuracy goal of 0.1 kHz on the absolute transition frequencies. Theoretically the feasibility of using metastable triplet helium atoms in the m = 0 state for atom interferometry is studied demonstrating favorable conditions, compared to the alkali atoms that are used traditionally, for a non-QED determination of the fine structure constant.

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“…[7]. In short, we use a liquid-nitrogen cooled dc discharge to excite helium atoms into the metastable triplet state.…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 91%

Section: Spectroscopymentioning

confidence: 99%

Section: Spectroscopymentioning

confidence: 99%

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Ultracold metastable helium: Ramsey fringes and atom interferometry

et al. 2016

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Precision metrology on the hydrogen atom in search for new physics

et al. 2013

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The Hydrogen atom has been the benchmark system throughout the history of atomic physics. This year we celebrate the centennial of the Bohr model [1], proposing the first quantum description of an atom and the rationale behind the Rydberg formula. This explanation of the spectrum of the H-atom ignited the quantum revolution. With the invention of the laser and the development of laser spectroscopic techniques the accuracy of spectroscopic measurements of the 1S-2S transition of hydrogen atom (natural linewidth 1.3 Hz) has improved by many orders of magnitude as shown in Figure 1, culminating now at an impressive 10 Hz or a relative accuracy of 4×10 −15 [2].

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