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Register a new userInvestigation of the Gravitational Potential Dependence of the Fine-Structure Constant Using Atomic Dysprosium
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Radio-frequency E1 transitions between nearly degenerate, opposite parity levels of atomic dysprosium were monitored over an eight month period to search for a variation in the fine-structure constant. During this time period, data were taken at different points in the gravitational potential of the Sun. The data are fitted to the variation in the gravitational potential yielding a value of $(-8.7 pm 6.6) times 10^{-6}$ for the fit parameter $k_alpha$. This value gives the current best laboratory limit. In addition, our value of $k_{alpha}$ combined with other experimental constraints is used to extract the first limits on k_e and k_q. These coefficients characterize the variation of m_e/m_p and m_q/m_p in a changing gravitational potential, where m_e, m_p, and m_q are electron, proton, and quark masses. The results are $k_e = (4.9 pm 3.9) times 10^{-5}$ and $k_q = (6.6 pm 5.2) times 10^{-5}$.
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Radio-frequency electric-dipole transitions between nearly degenerate, opposite parity levels of atomic dysprosium (Dy) were monitored over an eight-month period to search for a variation in the fine-structure constant, $alpha$. The data provide a rate of fractional temporal variation of $alpha$ of $(-2.4pm2.3)times10^{-15}$ yr$^{-1}$ or a value of $(-7.8 pm 5.9) times 10^{-6}$ for $k_alpha$, the variation coefficient for $alpha$ in a changing gravitational potential. All results indicate the absence of significant variation at the present level of sensitivity. We also present initial results on laser cooling of an atomic beam of dysprosium.
We propose a new probe of the dependence of the fine structure constant, alpha, on a strong gravitational field using metal lines in the spectra of white dwarf stars. Comparison of laboratory spectra with far-UV astronomical spectra from the white dwarf star G191-B2B recorded by the Hubble Space Telescope Imaging Spectrograph gives limits on the fractional variation of alpha of (Delta alpha/alpha)=(4.2 +- 1.6)x10^(-5) and (-6.1 +- 5.8)x10^(-5) from Fe V and Ni V spectra, respectively, at a dimensionless gravitational potential relative to Earth of (Delta phi) ~ 5x10^(-5). With better determinations of the laboratory wavelengths of the lines employed these results could be improved by up to two orders of magnitude.
A means to extract the fine-structure constant $alpha$ from precision spectroscopic data on one-electron ions is presented. We show that in an appropriately weighted difference of the bound-electron $g$ factor and the ground state energy, nuclear structural effects can be effectively suppressed. This method is anticipated to deliver an independent value of $alpha$ via existing or near-future combined Penning trap and x-ray spectroscopic technology, and enables decreasing the uncertainty of $alpha$ by orders of magnitude.
Measurements of the fine-structure constant alpha require methods from across subfields and are thus powerful tests of the consistency of theory and experiment in physics. Using the recoil frequency of cesium-133 atoms in a matter-wave interferometer, we recorded the most accurate measurement of the fine-structure constant to date: alpha = 1/137.035999046(27) at 2.0 x 10^-10 accuracy. Using multiphoton interactions (Bragg diffraction and Bloch oscillations), we demonstrate the largest phase (12 million radians) of any Ramsey-Borde interferometer and control systematic effects at a level of 0.12 parts per billion. Comparison with Penning trap measurements of the electron gyromagnetic anomaly ge-2 via the Standard Model of particle physics is now limited by the uncertainty in ge-2; a 2.5 sigma tension rejects dark photons as the reason for the unexplained part of the muons magnetic moment at a 99 percent confidence level. Implications for dark-sector candidates and electron substructure may be a sign of physics beyond the Standard Model that warrants further investigation.
We present a new measurement of the Newtonian gravitational constant G based on cold atom interferometry. Freely falling samples of laser-cooled rubidium atoms are used in a gravity gradiometer to probe the field generated by nearby source masses. In addition to its potential sensitivity, this method is intriguing as gravity is explored by a quantum system. We report a value of G=6.667 10^{-11} m^{3} kg^{-1} s^{-2}, estimating a statistical uncertainty of $pm$ 0.011 10^{-11} m^{3} kg^{-1} s^{-2} and a systematic uncertainty of $pm$ 0.003 10^{-11} m^{3} kg^{-1} s^{-2}. The long-term stability of the instrument and the signal-to-noise ratio demonstrated here open interesting perspectives for pushing the measurement accuracy below the 100 ppm level.
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