No abstract

Experimental searches for the electron electric dipole moment, de, probe new physics beyond the Standard Model. Recently, the ACME Collaboration set a new limit of |de| < 1.1 × 10 −29 e · cm [Nature 562, 355 (2018)], constraining time reversal symmetry (T) violating physics in the 3-100 TeV energy scale. ACME extracts de from the measurement of electron spin precession due to the thorium monoxide (ThO) molecule's internal electric field. This recent ACME II measurement achieved an order of magnitude increased sensitivity over ACME I by reducing both statistical and systematic uncertainties in the measurement of the electric dipole precession frequency. The ACME II statistical uncertainty was a factor of 1.7 above the ideal shot-noise limit. We have since traced this excess noise to timing imperfections. When the experimental imperfections are eliminated, we show that shot noise limit is attained by acquiring noise-free data in the same configuration as ACME II. arXiv:1907.00554v1 [physics.atom-ph] 1 Jul 2019

We demonstrate a simple and compact external cavity diode laser (ECDL), where light reflected from the tip of an optical fiber provides feedback, and an interference filter provides frequency selection. The ECDL combines ease of construction with robust operation and exhibits a linewidth of 50 kHz.

The 4f 6 7 F0 → 4f 6 5 D0 intra-configuration transition in Sm:SrF 2 is forbidden for Sm 2+ ions in the octahedrally symmetric substitution sites in SrF 2 . We report the direct observation of this transition using laser-induced fluorescence at cryogenic temperatures, and measurements of the excited state lifetime and the excitation cross section. To the best of our knowledge, this optical transition has the longest lived excited state ever observed in a solid.