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Register a new userHigh-precision spectroscopy of the HD+ molecule at the 1-p.p.b. level
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Recently we reported a high precision optical frequency measurement of the (v,L):(0,2)->(8,3) vibrational overtone transition in trapped deuterated molecular hydrogen (HD+) ions at 10 mK temperature. Achieving a resolution of 0.85 parts-per-billion (p.p.b.) we found the experimental value ($ u_0= 383,407,177.38(41)$ MHz) to be in agreement with the value from molecular theory ($ u_text{th}=383,407,177.150(15)$ MHz) within 0.6(1.1) p.p.b. [Biesheuvel et al., Nat. Commun. 7, 10385 (2016)]. This enabled an improved test of molecular theory (including QED), new constraints on the size of possible effects due to new physics, and the first determination of the proton-electron mass ratio from a molecule. Here, we provide the details of the experimental procedure, spectral analysis, and the assessment of systematic frequency shifts. Our analysis focuses in particular on deviations of the HD+ velocity distribution from thermal (Gaussian) distributions under the influence of collisions with fast ions produced during (laser-induced) chemical reactions, as such deviations turn out to significantly shift the hyperfine-less vibrational frequency as inferred from the saturated and Doppler-broadened spectrum, which contains partly unresolved hyperfine structure.
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Expectation values of the Breit operators and the $Q$ terms are calculated for HD$^+$ with the vibrational number $v=0-4$ and the total angular momentum $L=0-4$. Relativistic and radiative corrections to some ro-vibrational transition frequencies are determined. Numerical uncertainty in $R_{infty}alpha^2$ order correction is reduced to sub kHz or smaller. Our work provides an independent verification of Korobovs calculations [Phys. Rev. A {bf74}, 052506 (2006); {bf77}, 022509 (2008)].
We present a precise measurement of the lifetime of the 6p 2P_1/2 excited state of a single trapped ytterbium ion (Yb+). A time-correlated single-photon counting technique is used, where ultrafast pulses excite the ion and the emitted photons are coupled into a single-mode optical fiber. By performing the measurement on a single atom with fast excitation and excellent spatial filtering, we are able to eliminate common systematics. The lifetime of the 6p 2P_1/2 state is measured to be 8.12 +/- 0.02 ns.
The spin-magnetic moment of the proton $mu_p$ is a fundamental property of this particle. So far $mu_p$ has only been measured indirectly, analysing the spectrum of an atomic hydrogen maser in a magnetic field. Here, we report the direct high-precision measurement of the magnetic moment of a single proton using the double Penning-trap technique. We drive proton-spin quantum jumps by a magnetic radio-frequency field in a Penning trap with a homogeneous magnetic field. The induced spin-transitions are detected in a second trap with a strong superimposed magnetic inhomogeneity. This enables the measurement of the spin-flip probability as a function of the drive frequency. In each measurement the protons cyclotron frequency is used to determine the magnetic field of the trap. From the normalized resonance curve, we extract the particles magnetic moment in units of the nuclear magneton $mu_p=2.792847350(9)mu_N$. This measurement outperforms previous Penning trap measurements in terms of precision by a factor of about 760. It improves the precision of the forty year old indirect measurement, in which significant theoretical bound state corrections were required to obtain $mu_p$, by a factor of 3. By application of this method to the antiproton magnetic moment $mu_{bar{p}}$ the fractional precision of the recently reported value can be improved by a factor of at least 1000. Combined with the present result, this will provide a stringent test of matter/antimatter symmetry with baryons.
We report an experimental measurement of a light wavelength at which the ac electric polarizability equals zero for 87Rb atoms in the F=2 ground hyperfine state. The experiment uses a condensate interferometer both to find this tune-out wavelength and to accurately determine the light polarization for it. The wavelength lies between the D1 and D2 spectral lines at 790.03235(3) nm. The measurement is sensitive to the tensor contribution to the polarizability, which has been removed so that the reported value is the zero of the scalar polarizability. The precision is fifty times better than previous tune-out wavelength measurements. Our result can be used to determine the ratio of matrix elements |<5P3/2||d||5S1/2>/<5P1/2||d||5S1/2>|^2 = 1.99219(3), a 100-fold improvement over previous experimental values. Both the tune-out wavelength and matrix element ratio are consistent with theoretical calculations, with uncertainty estimates for the theory about an order of magnitude larger than the experimental precision.
The study of ultracold molecules tightly trapped in an optical lattice can expand the frontier of precision measurement and spectroscopy, and provide a deeper insight into molecular and fundamental physics. Here we create, probe, and image microkelvin $^{88}$Sr$_2$ molecules in a lattice, and demonstrate precise measurements of molecular parameters as well as coherent control of molecular quantum states using optical fields. We discuss the sensitivity of the system to dimensional effects, a new bound-to-continuum spectroscopy technique for highly accurate binding energy measurements, and prospects for new physics with this rich experimental system.
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