The 2 3 P 1 -2 3 P 2 interval in helium is measured using microwave separated oscillatory fields. Our measured result is 2 291 177.53Ϯ 0.35 kHz . A disagreement with theory of over 15 kHz indicates a major problem with two-electron QED calculations. If this disagreement is resolved, measurements of both 2 3 P fine-structure intervals at this accuracy would lead to a six-parts-per-billion determination of the fine-structure constant.The present work continues the long history of precision measurements of the 2 3 P fine structure of helium ͓1-5͔. The main goal of these measurements is to determine the finestructure constant, ␣, from the larger ͑29.6 GHz͒ 2 3 P 1 -2 3 P 0 interval with the smaller ͑2.3 GHz͒ 2 3 P 1 -2 3 P 2 interval testing the two-electron QED theoretical calculations necessary to determine ␣. The present work differs by 36 standard deviations from theory ͓6,7͔. If this discrepancy is resolved, measurements of both 2 3 P finestructure intervals at the current accuracy would determine ␣ to 6 ppb. The most precise determination of ␣ ͑0.37 ppb͒ is from the magnetic moment of the electron ͑g e -2͒ ͓8͔. Independent determinations of ␣ ͓9͔ are needed to allow g e -2 to test QED to 0.37 ppb ͑the most precise test of QED theory͒ and to search for physics beyond the standard model ͓8͔.In this 2 3 P measurement separated oscillatory fields ͑SOFs͒ are used, compared to previous measurements which used continuous fields for excitation ͓1-5͔. SOFs allow for narrower linewidths ͑0.8-1.7 MHz͒ than the 3.25 MHz natural linewidth and also allow for a variety of line shapes. Figure 1 shows the experimental setup. A thermal beam of 2 3 S 1 metastable He is created in a dc discharge ͓3͔ and the 2 3 S 1 ͑m =0͒ state is depopulated by repeatedly driving 2 3 S 1 ͑m =0͒ -2 3 P 0 with a linearly polarized 1.08 m diode laser ͑A in Fig. 1͒. 2 3 S 1 ͑m = Ϯ 1͒ atoms are driven up to 2 3 P 1 ͑m =0͒ by a 15 ns laser pulse ͑B1 in Fig. 1, pulsed using two passes through an acousto-optic modulator͒, which is followed by the two 2.3 GHz SOF microwave pulses ͓P1 and P2 of Fig. 1͑c͒, of duration D = 50, 100, or 150 ns and separated in time by T = 300, 400, 500, or 600 ns͔ which drive the 2 3 P 1 ͑m =0͒ -2 3 P 2 ͑m =0͒ transition. Atoms can decay to 2 3 S 1 ͑m =0͒ only if the microwave transition is driven since the 2 3 P 1 ͑m =0͒ -2 3 S 1 ͑m =0͒ branching ratio is zero. This 2 3 S 1 ͑m =0͒ population is excited to 2 3 P 0 with laser C and the resulting fluorescence is collected on a 77 K InGaAs photodiode.The microwave transitions are driven inside of a 50 ⍀ coaxial transmission line ͓Fig. 1͑a͔͒. To double the signal size, another laser beam ͑B2͒ repeats the experiment on the other side of the 50 ⍀ line ͓inset of Fig. 1͑a͔͒. Microwaves ͑referenced to a Rb clock͒ are pulsed using fast switches and amplified to P = 25-125 W by a solid-state amplifier. The relative phase of P1 and P2 is controlled by additional switches which direct the pulses through paths L1 or L2 that differ in length by a half wavelength ͑ / 2͒. Every 79 ms, the rela...

Slow antihydrogen (H) is produced within a Penning trap that is located within a quadrupole Ioffe trap, the latter intended to ultimately confine extremely cold, ground-state H[over ] atoms. Observed H[over ] atoms in this configuration resolve a debate about whether positrons and antiprotons can be brought together to form atoms within the divergent magnetic fields of a quadrupole Ioffe trap. The number of detected H atoms actually increases when a 400 mK Ioffe trap is turned on.

The 2(3)P(1)-to- 2(3)P(0) interval in atomic helium is measured using a thermal beam of metastable helium atoms excited to the 2(3)P state using a 1.08-microm diode laser. The 2(3)P(1)-to- 2(3)P(0) transition is driven by 29.6-GHz microwaves in a rectangular waveguide cavity. Our result of 29,616,950.9+/-0.9 kHz is the most precise measurement of helium 2(3)P fine structure. When compared to precise theory for this interval, this measurement leads to a determination of the fine-structure constant of 1/137.0359864(31).

For the first time a single trapped antiproton ( " p) is used to measure the " p magnetic moment " p . The moment " p ¼ " p S=ð@=2Þ is given in terms of its spin S and the nuclear magneton ( N ) by " p = N ¼ À2:792 845 AE 0:000 012. The 4.4 parts per million (ppm) uncertainty is 680 times smaller than previously realized. Comparing to the proton moment measured using the same method and trap electrodes gives " p = p ¼ À1:000 000 AE 0:000 005 to 5 ppm, for a proton moment p ¼ p S=ð@=2Þ, consistent with the prediction of the CPT theorem.

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The 2 3P1-to- 2 3P2 interval in atomic helium is measured using a thermal beam of metastable helium atoms excited to the 2 3P state using a 1.08-&mgr;m diode laser. The 2 3P1-to- 2 3P2 transition is driven by 2.29-GHz microwaves in a coaxial transmission line. Our result of 2 291 174.0+/-1.4 kHz is the most precise measurement of helium 2 3P fine structure. This measurement plays a key role in obtaining a new value for the fine-structure constant.

Aluminum, with its distinctively favorable dielectric characteristics down to deep ultraviolet (UV) regime, has recently emerged as a broad-band and low-cost alternative to noble metals. However, low Q-factor resonances (Q ∼ 2−4), offered by Al nanostructures, pose a fundamental bottleneck for many practical applications. Here, we show that it is possible to realize Al-nanoantenna with remarkably large extinction cross sections and strong resonance characteristics surpassing those of their noble metal counterparts. By quenching radiation damping through far-field coherent dipolar interactions, we experimentally demonstrate exceptionally narrow line width (∼15 nm) and high Q-factor (∼27) dipolar plasmonic resonances in the blue-violet region of the optical spectrum (∼3 eV) beyond the practical operational limits of traditional plasmonic metals. To realize high Q-factor Al resonators, we introduce a novel space mapping algorithm enabling inverse design of Al nanoantenna arrays at arbitrary sub/superstrate material interfaces with diminished radiative losses. We show that radiatively coupled Al nanoantenna arrays offer remarkably high-Q factor (27 ≤ Q ≤ 53) resonances over the entire visible spectrum and readily outperform similarly optimized silver (Ag) nanoantenna arrays in green-blue-violet wavelengths (≤550 nm) and near UV regime. This report shows that it is possible to realize high Q-factor aluminum resonators by suppressing radiative losses and that Al-based plasmonics holds enormous potential as a viable and low-cost alternative to noble metals. Our inverse-design technique, on the other hand, provides a general and efficient approach in engineering of high Q-factor resonator arrays, independently from the metals and sub/superstrates used.

Quartz surfaces and colloidal silica particles were derivatized with a poly(methyl methacrylate) copolymer containing spirobenzopyran (SP) photochromic molecules in the pendant groups at a concentration of 20 mol %. Two-photon near-IR excitation (approximately 780 nm) was then used to create chemically distinct patterns on the modified surfaces through a photochromic process of SP transformation to the zwitterionic merocyanine (MC) isomer. The derivatized colloids were approximately 10 times more likely to adsorb onto the photoswitched, MC regions. Surface coverage and adsorption kinetics have been compared to the mean-field model of irreversible monolayer adsorption.