Explore the vast range of titles available.

The publication of the 2021 atomic weights (1) leads to the following updated values for the atomic weights of the platinum group of elements: ruthenium 101.07 ± 0.02; rhodium 102.90549 ± 0.00002; palladium 106.42 ± 0.01; osmium 190.23 ± 0.03; iridium 192.217 ± 0.002; platinum 195.084 ± 0.009.

A very precise measurement of the magnetic moment of a single electron bound to a carbon nucleus, combined with a state-of-the-art calculation in the framework of bound-state quantum electrodynamics, gives a new value of the atomic mass of the electron that is more precise than the currently accepted one by a factor of 13. Electron mass to unprecedented precision The atomic mass of the electron is a key parameter for fundamental physics. A precise determination is a challenge because the mass is so low. Sven Sturm and colleagues report on a new determination of the electron's mass in atomic units. The authors measured the magnetic moment of a single electron bound to a reference ion (a bare nucleus of carbon-12). The results were analysed using state-of-the-art quantum electrodynamics theory to yield a mass value with a precision that exceeds the current literature value by more than an order of magnitude. The quest for the value of the electron’s atomic mass has been the subject of continuing efforts over the past few decades 1 , 2 , 3 , 4 . Among the seemingly fundamental constants that parameterize the Standard Model of physics 5 and which are thus responsible for its predictive power, the electron mass m e is prominent, being responsible for the structure and properties of atoms and molecules. It is closely linked to other fundamental constants, such as the Rydberg constant R ∞ and the fine-structure constant α (ref. 6 ). However, the low mass of the electron considerably complicates its precise determination. Here we combine a very precise measurement of the magnetic moment of a single electron bound to a carbon nucleus with a state-of-the-art calculation in the framework of bound-state quantum electrodynamics. The precision of the resulting value for the atomic mass of the electron surpasses the current literature value of the Committee on Data for Science and Technology (CODATA 6 ) by a factor of 13. This result lays the foundation for future fundamental physics experiments 7 , 8 and precision tests of the Standard Model 9 , 10 , 11 .

Charge, parity, and time reversal (CPT) symmetry implies that a particle and its antiparticle have the same mass. The antiproton-to-electron mass ratio Mp̄/me can be precisely determined from the single-photon transition frequencies of antiprotonic helium. We measured 13 such frequencies with laser spectroscopy to a fractional precision of 2.5 x 1O⁻⁹ to 16 x 1O⁻⁹. About 2 x 10⁹ antiprotonic helium atoms were cooled to temperatures between 1.5 and 1.7 kelvin by using buffer-gas cooling in cryogenic lowpressure helium gas; the narrow thermal distribution led to the observation of sharp spectral lines of small thermal Doppler width. The deviation between the experimental frequencies and the results of three-body quantum electrodynamics calculations was reduced by a factor of 1.4 to 10 compared with previous single-photon experiments. From this, Mp̄/me was determined as 1836.1526734(15), which agrees with a recent proton-toelectron experimental value within 8 x 1O⁻¹⁰.

Abstract Non-target screening (NTS) based on high-resolution mass spectrometry (HRMS) is necessary to comprehensively characterize per- and polyfluoroalkyl substances (PFAS) in environmental, biological, and technical samples due to the very limited availability of authentic PFAS reference standards. Since in trace analysis, MS/MS information is not always achievable and only selected PFAS are present in homologous series, further techniques to prioritize measured HRMS data (features) according to their likelihood of being PFAS are highly desired due to the importance of efficient data reduction during NTS. Kaufmann et al. (J AOAC Int, 2022) presented a very promising approach to separate selected PFAS from sample matrix features by plotting the mass defect (MD) normalized to the number of carbons (MD/C) vs. mass normalized to the number of C (m/C). We systematically evaluated the advantages and limitations of this approach by using ~ 490,000 chemical formulas of organic chemicals (~ 210,000 PFAS, ~ 160,000 organic contaminants, and 125,000 natural organic matter compounds) and calculating how efficiently, and especially which, PFAS can be prioritized. While PFAS with high fluorine content (approximately: F/C > 0.8, H/F < 0.8, mass percent of fluorine > 55%) can be separated well, partially fluorinated PFAS with a high hydrogen content are more difficult to prioritize, which we discuss for selected PFAS. In the MD/C-m/C approach, even compounds with highly positive MDs above 0.5 Da and hence incorrectly assigned to negative MDs can still be separated from true negative mass defect features by the normalized mass (m/C). Furthermore, based on the position in the MD/C-m/C plot, we propose the estimation of the fluorine fraction in molecules for selected PFAS classes. The promising MD/C-m/C approach can be widely used in PFAS research and routine analysis. The concept is also applicable to other compound classes like iodinated compounds.

Nuclear β -decay provides a laboratory for investigating weak decays occurring inside the nuclear medium. This provides information on the resulting subtle nuclear and atomic effects, and on the underlying interaction and the properties of the particles that are involved, particularly of the neutrino. The Q value of the decay corresponds to the energy equivalent of the mass difference between parent and daughter atoms, and can be precisely and accurately measured using Penning trap mass spectrometry. In this paper we discuss Penning trap Q value measurements for forbidden β -decays of long-lived primordial nuclides, and for a subset of β -unstable nuclides that could potentially undergo a very low energy decay to an excited state in the daughter nucleus. We discuss applications of these measurements to tests of systematics in detectors that perform precise β -spectrum measurements, as inputs for theoretical shape factor, electron branching ratio and half-life calculations, and to identify nuclides that could serve as new candidates in direct neutrino mass determination experiments.

The neutral muonic helium atom may be regarded as the heaviest isotope of the hydrogen atom, with a mass of approximately 4.1 atomic mass units (⁴.¹H), because the negative muon almost perfectly screens one proton charge. We report the reaction rate of ⁴.¹H with ¹H₂ to produce ⁴.¹H¹H + ¹H at 295 to 500 kelvin. The experimental rate constants are compared with the predictions of accurate quantum-mechanical dynamics calculations carried out on an accurate Born-Huang potential energy surface and with previously measured rate constants of ⁰.¹¹H (where ⁰.¹¹H is shorthand for muonium). Kinetic isotope effects can be compared for the unprecedentedly large mass ratio of 36. The agreement with accurate quantum dynamics is quantitative at 500 kelvin, and variational transition-state theory is used to interpret the extremely low (large inverse) kinetic isotope effects in the 10⁻⁴ to 10⁻² range.

rs Summaries of mass spectrometry (MS) data relating, firstly, to ions of the heaviest nondegraded molecules and larger particles and, secondly, to highly accurate mass ( m / z value) measurements are presented. Atomic masses were measured with relative accuracy up to 0.01–0.1 ppb, masses of petroleum constituents and other low-molecular-weight compounds were determined with accuracy up to 1–10 ppb. Ions of proteins with molecular weights >150 kDa, their large complexes, and other bioparticles, and also nanoparticles with masses up to 30 GDa have been recorded. In such research, electrospray ionization, including native MS versions, as well as various versions of high/ultrahigh-resolution MS, and charge detection MS are prevalent. Trends of development and MS records are briefly discussed.

Atomic mass measurements are essential for obtaining several of the fundamental constants. The most precise atomic mass measurements, at the 10−10 level of precision or better, employ measurements of cyclotron frequencies of single ions in Penning traps. We discuss the relation of atomic masses to fundamental constants in the context of the revised SI. We then review experimental methods, and the current status of measurements of the masses of the electron, proton, neutron, deuteron, tritium, helium-3, helium-4, oxygen-16, silicon-28, rubidium-87, and cesium-133. We conclude with directions for future work.

Significant advances in Penning trap measurements of atomic masses and mass ratios of the proton, deuteron, triton, helion, and alpha-particle have occurred in the last five years. These include a measurement of the mass of the deuteron against 12C with 8.5 × 10−12 fractional uncertainty; resolution of vibrational levels of H2+ as mass and the application of a simultaneous measurement technique to the H2+/D+ cyclotron frequency ratio, yielding a deuteron/proton mass ratio at 5 × 10−12; new measurements of HD+/3He+, HD+/T+, and T+/3He+ leading to a tritium beta-decay Q-value with an uncertainty of 22 meV, and atomic masses of the helion and triton at 13 × 10−12; and a new measurement of the mass of the alpha-particle against 12C at 12 × 10−12. Some of these results are in strong disagreement with previous values in the literature. Their impact in determining a precise proton/electron mass ratio and electron atomic mass from spectroscopy of the HD+ molecular ion is also discussed.

Ultrasonic melt processing attracts considerable interest from both academic and industrial communities as a promising route improving melt quality. The significance of this problem is predetermined by the matter liquid state problem. In paper the ultrasound absorption and propagation speed vS temperature are measured using multiple groups of samples, each group heated to a different temperature. This paper summaries the results on the evaluation of ultrasound absorption and the propagation speed, for calculating the ultrasound propagation speed in solutions, studies of the nucleation, growth and fragmentation of particles in liquid melts. It has been proven that melts with semiconductor properties are micro-inhomogeneous due to the existence of clusters in their atomic matrix. These results provide valuable new insights and knowledge that are essential for upscaling ultrasonic melt processing to industrial level.