Testing Quantum Electrodynamics in the Lowest Singlet State of Neutral Beryllium-9

Abstract

We report spectroscopic results on the 2s2p^{1}P_{1} state in neutral atomic beryllium-9. The absolute frequency for the center of gravity is determined to be 42 565.4501(13) cm^{-1}, a factor of 130 more precise than the previous experimental measurement. The result is in agreement with and a factor of 8 more precise than the current best theoretical estimate of 42 565.441(11) cm^{-1}, which was calculated including the effects of quantum electrodynamics. Because of the large natural linewidth of the transition, the hyperfine constants were not able to be extracted to high precision.

Resonant two-photon spectroscopy of the 2s3d 1D2 level of neutral BeCook1, Vira2, Williams3 2020Phys. Rev. A7230View full textAdd to dashboardCite

“…For the individual 2s 2 1 S 0 − 2s2p 1 P 1 and 2s2p 1 P 1 − 2s3d 1 D 2 transition energies, we conservatively incorporate the possibility that our spectral feature may be dominated by transitions to/from one of the intermediate or excited hyperfine levels by including as well the 37 MHz spectral width observed in our previous 1 P 1 saturated absorption measurements into our uncertainty budget. We find 42 565.4503( 14) cm −1 for the 2s 2 1 S 0 − 2s2p 1 P 1 transition, in agreement with our previous measurement of 42 565.4501(13) cm −1 [4]. For the 2s2p 1 P 1 − 2s3d 1 D 2 transition energy we find 21 862.9529( 14) cm −1 , in agreement with and a factor of 36× more precise than the previous experimental result [13].…”

“…Measurements of the 2s 2 1 S 0 − 2s2p 1 P 1 transition energy and ionization threshold of neutral 9 Be hold particular interest in serving as tests of the latest nonrelativistic wavefunction calculation methods and incorporation of leading relativistic and quantumelectrodynamic (QED) corrections. Puchalski et al, using explicitly correlated Gaussian (ECG) basis sets while taking into account relativistic, QED, and finite nuclear mass effects, calculated the 2s 2 1 S 0 − 2s2p 1 P 1 transition energy to be 42 565.441(11) cm −1 [1], with a QED shift of 1.048(9) cm −1 , a prediction verified by our recent saturated absorption measurements of this transition which found 42 565.4501(13) cm −1 [4].…”

“…Figure 4 shows the experimental setup for the two-step absorption measurement. We use a commercial oven at 1200 • C to produce a collimated beryllium beam with a transverse temperature less than 1 K, as described in [4], and a frequency-quadrupled Ti:Sapphire (Ti:S) laser (MSquared Lasers) to address the 1 S 0 − 1 P 1 transition at 234.9 nm. A Toptica Photonics external cavity diode laser (ECDL) at 457.4 nm is used to address the…”

“…As in Ref. [4], we reference the frequency-doubled output of the Ti:S at 470 nm to a calibrated, temperature-stabilized ultralow-expansion (ULE) cavity [19] using an offset sideband lock [20]; in this experiment, the 457 nm light is simultaneously referenced to the same ULE We drive the high-frequency fiber EOM with the combined outputs f s1 and f s2 of two RF signal generators (SRS SG384 and SG382) to allow calibrated, independent frequency scans of the two lasers. After the fiber EOM, each beam has high-frequency, tunable sidebands at both f s1 and f s2 in addition to the fixed 20 / 12.5 MHz modulation (as well as small features at f s1 ± f s2 ).…”

Ground and excited S1 states of the beryllium atom

“…The purpose of the present work is to demonstrate the efficiency of the all-electron explicitly correlated Gaussian (ECG) functions in variational calculations of ground and excited atomic states and obtain highly accurate, benchmark results for one of the most heavily used workbenches of the electronic structure theory and the experiment [1] -the beryllium atom. In this work we consider the ground and the lowest three excited 1 S states of Be.…”