Atomic Species Research Articles

Cavity Microscope for Micrometer-Scale Control of Atom-Photon Interactions

Cavity quantum electrodynamics offers the possibility of observing and controlling the motion of a few or individual atoms, enabling the realization of various quantum technological tasks such as quantum enhanced metrology or quantum simulation of strongly correlated matter. A core limitation of these experiments lies in the mode structure of the cavity field, which is hard coded in the shape and geometry of the mirrors. As a result, most applications of cavity QED trade spatial resolution for enhanced sensitivity. Here, we propose and demonstrate a cavity-microscope device capable of controlling in space and time the coupling between atoms and light in a single-mode high-finesse cavity, reaching a spatial resolution an order of magnitude lower than the cavity-mode waist. This is achieved through local Floquet engineering of the atomic level structure, imprinting a corresponding atom-field coupling. We illustrate this capability by engineering micrometer-scale coupling, using cavity-assisted atomic measurements and optimization. Our system forms an optical device with a single optical axis, has the same footprint and complexity as a standard Fabry-Perot cavity or confocal lens pair, and can be used for any atomic species. This technique opens a wide range of perspectives, from ultrafast cavity-enhanced midcircuit readout to the quantum simulation of fully connected models of quantum matter such as the Sachdev-Ye-Kitaev model. Published by the American Physical Society 2024

Tailoring Atomic Metal Species for Electrochemical-Driven Urea Synthesis Coupled with CO2 and Nitrogen Sources in Aqueous Media

Tailoring Atomic Metal Species for Electrochemical-Driven Urea Synthesis Coupled with CO2 and Nitrogen Sources in Aqueous Media

The GAPS programme at TNG

Context. Atmospheric characterisation plays a key role in the study of exoplanetary systems, giving hints about the current and past conditions of the planets. The information retrieved from the analysis of pivotal lines such as the Hα and He I triplet allow us to constrain the evolutionary path of the planets due to atmospheric photo-evaporation. After focussing for many years on ultra-hot Jupiters, atmospheric characterisation is slowly moving towards smaller and colder planets, which are harder to study due to the difficulties in extracting the planetary signal and which require more precise analysis. Aims. We aim to characterise the atmosphere of TOI-5398 b (P ~ 10.59 days), the outer warm Saturn orbiting a young (~650 Myr) G-type star that also hosts the small inner planet TOI-5398 c (P ~ 4.77 days). Both planets are suitable for atmospheric probing due to the closeness to their host star, which results in strong photo-evaporation processes, especially the larger outer one with an estimated transmission spectroscopy metric of 288 (higher than those of several well-known hot Jupiters). Methods. We investigated the atmosphere of planet b, analysing the data collected during a transit with HARPS-N and GIANO-B high-resolution spectrographs, employing both cross-correlation and single-line analysis to study the presence of atomic species. Incidentally, we recorded the simultaneous transit of planet c, and hence we also focussed on discerning the origin of the signal. We expect planet b to be the cause of the detected signal, since, according to existing evaporation models, it is currently expected to lose more mass than planet c. Results. We detected the presence of Hα and He I triplets, two markers of the photo-evaporation processes predicted for the system, retrieving a height in the atmosphere of 2.33 Rp and 1.65 Rp, respectively. We confirmed these predictions by employing the models computed with the ATES software, which predict a He I absorption arising from planet b comparable with the observed one. Moreover, the ATES models suggested an He/H ratio of 1/99 to match our observations. The investigation of atomic species led to the detection of an Na I doublet via single-line analysis, while the cross-correlation did not return a detection for any of the atomic species investigated.

Influence of the C + H2O -> H2CO solid-state reaction onastrochemical networks and the formation of complex organic molecules

The solid-state reaction C + H$_2$O rightarrow H$_2$CO has recently been studied experimentally and claimed as a new `non-energetic' pathway to complex organic and prebiotic molecules in cold astrophysical environments. We compared results of astrochemical network modelling with and without the C + H$_2$O surface reaction. A typical, generic collapse model in which a dense core forms from initially diffuse conditions was used along with the astrochemical kinetics model MAGICKAL. The inclusion of the reaction does not notably enhance the abundance of formaldehyde itself; however, it significantly enhances the abundance of methanol (formed by the hydrogenation of formaldehyde) on the dust grains at early times, when the high gas-phase abundance of atomic C leads to relatively rapid adsorption onto the grain surfaces. As a result, the gas-phase abundance of methanol is also increased due to chemical desorption, quickly reaching abundances close to sim 10$^ $ n$_H$, which decline strongly under late-time, high-density conditions. The reaction also influences the abundances of simple ice species, with the CO$_2$ abundance increased in the earliest, deepest ice layers, while the water-ice abundance is somewhat depressed. The abundances of various complex organic molecules are also affected, with some species becoming more abundant and others less. When gas-phase atomic carbon becomes depleted, the grain-surface chemistry returns to behaviour that would be expected if there had been no new reaction. Our results show that fundamental reactions involving the simplest atomic and molecular species can be of great importance for the evolution of astrochemical reaction networks, thus providing motivation for future experimental and theoretical studies.

Constructing electron-enriched Cu-Mn binuclear sites for enhanced catalytic ozonation toward wastewater purification

Rational construction of electron-enriched active sites in single-atom catalysts to accelerate interfacial electron transfer and boost catalytic ozonation activity is still a challenging task. Herein, electron-enriched Cu-Mn binuclear sites were successfully immobilized onto defect-rich N-doped carbon (Cu-Mn/NvC) in activating O3 for degradation of organic pollutants with high ionization potential from water. The Cu-Mn/NvC with Cu-Nv-Mn sites achieves almost 100 % removal of 4-chlorophenol in 60 min by catalytic ozonation with a degradation rate of 0.067 min−1, which is 3.94 times faster than Mn/NC, exceeding the reported values. The nonradicals of surface atomic oxygen species (*O/*OO) and singlet oxygen (1O2) are the dominant ROS responsible for contaminants degradation. The Cu-Nv-Mn sites can capture electrons from nitrogen vacancies, acting as electron enrichment centers that provide more electrons to O3. The Cu doping elevates Mn d-band center closer to the Fermi energy level and decreases the adsorption energy by 0.494 eV, significantly accelerating electron transfer from the Mn d-bands to the 2p orbital of O3, which enhances the activation of O3 to generate *O/*OO and 1O2 and thus improves the degradation of organic pollutants. Additionally, the excellent catalytic activity towards real wastewater and exceptional reusability after ten cycles demonstrate the superiority of the proposed system for practical application in wastewater treatment. This study provides an efficient pathway for activating O3 by accelerating interfacial electron transfer via the design of electron-rich metal dual-atom sites in carbon-based catalysts.

Single-photon large-momentum-transfer atom interferometry scheme for Sr or Yb atoms with application to determining the fine-structure constant

The leading experimental determinations of the fine-structure constant α currently rely on atomic photon-recoil measurements from Ramsey-Bordé atom interferometry with large-momentum transfer to provide an absolute mass measurement. We propose an experimental scheme for an intermediate-scale differential atom interferometer to measure the photon recoil of neutral atomic species with a single-photon optical clock transition. We calculate trajectories for our scheme that optimize the recoil phase while nullifying the undesired gravity-gradient phase by considering independently launching two clouds of ultracold atoms with the appropriate initial conditions. For Sr and Yb, we find an atom interferometer of height 3 m to be sufficient for an absolute mass measurement precision of Δm/m∼1×10−11 with current technology. Such a precise measurement would halve the current uncertainty in α, an uncertainty that would no longer be limited by an absolute mass measurement. The removal of this limitation would allow the current uncertainty in α to be reduced by a factor of 10 by corresponding improvements in relative mass measurements, thus paving the way for higher-precision tests of the standard model of particle physics. Published by the American Physical Society 2024

The influence of continuum lowering on the equilibrium composition of plasma: case study of laser-induced plasma on a WC–Cu target

Abstract Composition of plasma obtained by laser ablation of cermet WC-Cu is calculated under the assumption of local thermodynamical equilibrium. Special attention is paid to the effect of lowering the ionization potential, the influence of which in the Saha equations is reflected both through the exponential Boltzmann term and through the partition functions of atomic and ionic species present in the plasma. The effect on these two terms are separated and quantified. It has been shown that the correction of the partition functions due to the reduction of the ionization potential is of greater importance than the correction of Boltzmann term, at higher temperatures for atomic species. It is thus necessary for the precise determination of the plasma composition, especially at higher temperatures. The effect of lowering the ionization potential on different types of atoms as well as on different ionic states is analyzed. Тhe change of the partition function due to the lowering of ionization energy affects also the concentration of single charged ions in an amount comparable to the correction of the Boltzmann term.

Mn-Fe Dual-Metal Assemblages on Carbon-Coated Al2O3 Spheres for Catalytic Ozonation Oxidation: Structure, Performance, and Reaction Mechanism.

Catalysts with high catalytic activity and low production cost are important for industrial application of heterogeneous catalytic ozonation (HCO). In this study, we designed a carbon-coated aluminum oxide carrier (C-Al2O3) and reinforced it with Mn-Fe bimetal assemblages to prepare a high-performance catalyst Mn-Fe/C-Al2O3. The results showed that the carbon embedding significantly improved the abundance of surface oxygen functional groups, conductivity, and adsorption capacity of γ-Al2O3, while preserving its exceptional mechanical strength as a carrier. The prepared Mn-Fe/C-Al2O3 catalyst exhibited satisfactory catalytic ozonation activity and stability in the degradation of p-nitrophenol (PNP). Electron paramagnetic resonance (EPR) and quenching experiments reveal that radical ( ⋅ OH and ⋅ O2 ⋅ ) and nonradical oxidation (1O2) dominated the PNP degradation process. Theoretical calculations corroborated that the anchored atomic Fe and Mn sites regulated the local electronic structure of the catalyst. This modulation effectively promoted the activation of O3 molecules, resulting in the generation of atomic oxygen species (AOS) and reactive oxygen species (ROS). The economic analysis on Mn-Fe/C-Al2O3 revealed that it was a cost-competitive catalyst for HCO. This study not only deepens the understanding on the reaction mechanism of HCO with transition metal/carbon composite catalysts, also provides a high-performance and cost-competitive ozone catalyst for prospective application.

LiDB: Database of atomic radiative lifetimes for plasma processes

LiDB is a database of molecular radiative lifetimes (Owens et al., 2023), created to aid in the modelling of radiative effects in low-temperature plasmas. Here, we report the addition of atomic radiative lifetimes to LiDB. Datasets are generated for neutral and singly-charged atomic species based on energy levels, transitions, and transition probabilities extracted from the National Institute of Standards and Technology (NIST) Atomic Spectra Database (ASD). The main data output of LiDB is radiative lifetimes of atomic states defined uniquely by atomic term symbols and electronic configurations. The effects of the total angular momentum quantum number J on the lifetimes are averaged over using an atomic state lumping procedure. LiDB also provides partial lifetimes which yield information on the dominant radiative decay channels from each state. Datasets are available for 35 neutral and 19 singly-charged atoms with new species to be added in the future. LiDB is freely available at www.exomol.com/lidb where users can dynamically view atomic and molecular datasets or use an application programming interface (API) to request data.

Ambient-condition acetylene hydrogenation to ethylene over WS2-confined atomic Pd sites

Ambient-condition acetylene hydrogenation to ethylene (AC-AHE) is a promising process for ethylene production with minimal additional energy input, yet remains a great challenge due to the difficulty in the coactivation of acetylene and H2 at room temperature. Herein, we report a highly efficient AC-AHE process over robust sulfur-confined atomic Pd species on tungsten sulfide surface. The catalyst exhibits over 99% acetylene conversion with a high ethylene selectivity of 70% at 25 oC, and a record space-time yield of ethylene of 1123 molC2H4 molPd−1 h−1 under ambient conditions, which is nearly four times that of the typical Pd1Ag3/Al2O3 catalyst, and exhibiting superior stability of over 500 h. We demonstrate that the confinement of Pd-S coordination induces positively-charged atomic Pdδ+, which not only facilitates C2H2 hydrogenation but also promotes C2H4 desorption, thereby enabling a high conversion of C2H2 to C2H4 at room temperature while suppressing over-hydrogenation to C2H6.

A Gravitational-like Relationship of Dispersion Interactions is Exhibited by 40 Pairs of Molecules and Noble Gas Atoms.

We present computational results of many-body dispersion (MBD) interactions for 40 pairs of molecular and atomic species: hydrocarbons, silanes, corresponding fluorinated derivatives, pairs which have multiple H---H contacts between the molecules, as well as pairs having π-π interactions, and pairs of noble gases. The calculations reveal that the MBD stabilization energy (EDISP,MBD) obeys a global relationship, which is gravitational-like. It is proportional to the product of the masses of the two molecules (M1M2) and inversely proportional to the corresponding distances between the molecular centers-of-mass (RCOM-COM) or the H---H distances of the atoms mediating the interactions of the two molecules (RH-H). This relationship reflects the interactions of instantaneous dipoles, which are formed by the ensemble of bonds/atoms in the interacting molecules. Using the D4-corrected dispersion energy (EDISP,D4), which accounts for three-body interactions, we find that the EDISP,MBD and EDISP,D4 data sets are strongly correlated. Based on valence-bond modeling, the dispersion interactions occur primarily due to the increased contributions of the oscillating-ionic VB structures which maintain favorable electrostatic interactions; the [Sub─C+:H-+H:C-─Sub] and [Sub─C:-+H -H:C+─Sub] structures; Sub symbolizes general residues. This augmented contribution is complemented by simultaneously diminished-weights of the destabilizing pair of structures, [Sub─C+:H--H:C+─Sub] and [Sub─:C- H++H:C-─Sub]. The local charges are propagated to the entire ensemble of bonds/atoms by partially charging the Sub residues, thus bringing about the "gravitational-like" dependence of dispersion.

Optical manipulation of spin states in ultracold magnetic atoms via an inner-shell hz transition

Lanthanides, like erbium and dysprosium, have emerged as powerful platforms for quantum-gas research due to their diverse properties, including a significant large spin manifold in their absolute ground state. However, effectively exploiting the spin richness necessitates precise manipulation of spin populations, a challenge yet to be fully addressed in this class of atomic species. In this work, we present an all-optical method for deterministically controlling the spin composition of a dipolar bosonic erbium gas, based on a clocklike transition in the telecom window at 1299nm. The atoms can be prepared in just a few tens of microseconds in any spin-state composition using a sequence of Rabi-pulse pairs, selectively coupling Zeeman sublevels of the ground state with those of the long-lived clocklike state. Finally, we demonstrate that this transition can also be used to create spin-selective light shifts, thus fully suppressing spin-exchange collisions. These experimental results unlock exciting possibilities for implementing advanced spin models in isolated, clean, and fully controllable lattice systems. Published by the American Physical Society 2024

Experimental realization of multiple frequency photoassociation in an optical dipole trap.

The generation of cold molecules is an important topic in the field of cold atoms and molecules and has received relevant advanced research attention in ultracold chemistry, quantum computation, and quantum metrology. With a high atomic phase space density, optical dipole traps have been widely used to prepare, trap, and study cold molecules. In this work, Rb2 molecules were photoassociated in a magneto-optical trap to obtain a precise rovibrational spectrum, which provided accurate numerical references for the realization of multiple frequency photoassociation. By meeting the harsh requirements of photoassociation in optical dipole traps, the cold molecule photoassociation process was well explored, and different photoassociation resonances were simultaneously addressed in a single optical dipole trap. This method can be universally extended to simultaneously photoassociate cold molecules with different internal states or atomic species in a single optical dipole trap, thus advancing generous cold molecule studies such as cold molecule collision dynamics.

Local structure maturation in high entropy oxide (Mg,Co,Ni,Cu,Zn)1‐x(Cr,Mn)xO thin films

AbstractHigh entropy oxides (HEOs) have garnered much interest due to their available high degree of tunability. Here, we study the local structure of (MgNiCuCoZn)0.167(MnCr)0.083O, a composition based on the parent HEO (MgNiCuCoZn)0.2O. We synthesized a series of thin films via pulsed laser deposition at incremental oxygen partial pressures. X‐ray diffraction shows lattice parameters to decrease with increased pO2 pressures until the onset of phase separation. X‐ray absorption fine structure shows that specific atomic species in the composition dictate the global structure of the material as Cr, Co, and Mn shift to energetically favorable coordination with increasing pressure. Transmission electron microscopy analysis on a lower‐pressure sample exhibits a rock salt structure, but the higher‐pressure sample reveals reflections reminiscent of the spinel structure. In all, these findings give a more complete picture of how (MgNiCuCoZn)0.167(MnCr)0.083O forms with varying initial conditions and advances fundamental knowledge of cation behavior in high entropy oxides.

Structural and Dynamical Effects of the CaO/SrO Substitution in Bioactive Glasses.

Silicate glasses containing silicon, sodium, phosphorous, and calcium have the ability to promote bone regeneration and biodegrade as new tissue is generated. Recently, it has been suggested that adding SrO can benefit tissue growth and silicate glass dissolution. Motivated by these recent developments, the effect of SrO/CaO-CaO/SrO substitution on the local structure and dynamics of Si-Na-P-Ca-O oxide glasses has been studied in this work. Differential thermal analysis has been performed to determine the thermal stability of the glasses after the addition of strontium. The local structure has been studied by neutron diffraction augmented by Reverse Monte Carlo simulation, and the local dynamics by neutron Compton scattering and Raman spectroscopy. Differential thermal analysis has shown that SrO-containing glasses have lower glass transition, melting, and crystallisation temperatures. Moreover, the addition of the Sr2+ ions decreased the thermal stability of the glass structure. The total neutron diffraction augmented by the RMC simulation revealed that Sr played a similar role as Ca in the glass structure when substituted on a molar basis. The bond length and the coordination number distributions of the network modifiers and network formers did not change when SrO (x = 0.125, 0.25) was substituted for CaO (25-x). However, the network connectivity increased in glass with 12.5 mol% CaO due to the increased length of the Si-O-Si interconnected chain. The analysis of Raman spectra revealed that substituting CaO with SrO in the glass structure dramatically enhances the intensity of the high-frequency band of 1110-2000 cm-1. For all glasses under investigation, the changes in the relative intensities of Raman bands and the distributions of the bond lengths and coordination numbers upon the SrO substitution were correlated with the values of the widths of nuclear momentum distributions of Si, Na, P, Ca, O, and Sr. The widths of nuclear momentum distributions were observed to soften compared to the values observed and simulated in their parent metal-oxide crystals. The widths of nuclear momentum distributions, obtained from fitting the experimental data to neutron Compton spectra, were related to the amount of disorder of effective force constants acting on individual atomic species in the glasses.

Light-induced fictitious magnetic fields for quantum storage in cold atomic ensembles

In this paper, we have demonstrated that optically generated fictitious magnetic fields can be utilized to extend the lifetime of quantum memories in cold atomic ensembles. All the degrees of freedom of an AC Stark shift, such as polarization, spatial profile, and temporal waveform, can be readily controlled in a precise manner. Temporal fluctuations over several experimental cycles and spatial inhomogeneities along a cold atomic gas have been compensated by an optical beam. The advantage of employing fictitious magnetic fields for quantum storage lies in the speed and spatial precision with which these fields can be synthesized. Our simple and versatile technique can find widespread application in coherent pulse and single-photon storage across various atomic species. Published by the American Physical Society 2024

Bi-intercalated epitaxial graphene on SiC(0001)

Abstract The intercalation of graphene with suitable atomic species is one of the most frequently applied methods to decouple the graphene layer from the substrate in order to establish the classical electronic properties of graphene. In this context, we studied the bismuth (Bi) intercalation of the (6√3×6√3)R30° reconstructed so-called "zeroth layer graphene'' on SiC(0001). 
As reported earlier by Sohn et al. [J. Korean Phys. Soc. 78, 157 (2021)], two phases are formed depending on the amount of intercalated Bi, which in turn is controlled by the annealing temperature: The α phase, showing a 1×1 periodicity with respect to the substrate, and, at higher temperatures, the √3×√3 reconstructed β phase. We characterise both phases and the transformation from the α to the β phase by photoelectron spectroscopy, normal incidence x-ray standing waves, electron diffraction and electron microscopy. We clearly see an almost complete intercalation of the graphene layers in both phases, with strong (covalent) interaction between the topmost Si atoms of the substrate and the Bi intercalant, but only weak (van der Waals) interaction between Bi and the graphene layer. The n-doping of the graphene found for the α phase decreases continuously during the phase transformation, in agreement with a reduced density of the Bi intercalating layer. Missing core level shifts of the surface species as well as the normal incidence x-ray standing waves results indicate that all surface Si atoms remain saturated during the transition and no dangling bonds are formed. Low energy electron microscopy and diffraction reveal the coexistance of both phases after annealing to intermediate temperatures and allow a quantitative analysis of island sizes and numbers.

High-throughput dataset of impurity adsorption on common catalysts in biomass upgrading applications

An extensive dataset consisting of adsorption energies of pernicious impurities present in biomass upgrading processes on common catalysts and support materials has been generated. This work aims to inform catalyst and process development for the conversion of biomass-derived feedstocks to fuels and chemicals. A high-throughput workflow was developed to execute density functional theory calculations for a diverse set of atomic (Al, B, Ca, Cl, Fe, K, Mg, Mn, N, Na, P, S, Si, Zn) and molecular (COS, H2S, HCl, HCN, K2O, KCl, NH3) species on 35 unique surfaces for transition-metal (Ag, Au, Co, Cu, Fe, Ir, Ni, Pd, Pt, Re, Rh, Ru) and metal-oxide (Al2O3, MgO, anatase-TiO2, rutile-TiO2, ZnO, ZrO2) catalysts and supports. Approximately 3,000 unique adsorption geometries and corresponding adsorption energies were obtained.

Coarsening kinetics of alloy-doped nanoporous metals

Due to their high surface-to-volume ratios, nanoporous metals are being explored for a range of catalytic and structural applications. However, these materials have thermodynamically unstable morphologies and degrade via coarsening at elevated temperatures. One potential mitigation strategy is to introduce atomic species that inhibit diffusional transport, but there is limited mechanistic understanding. To begin addressing this knowledge gap, the impact of a slow-diffusing dopant on the coarsening behavior of a nanoporous metal is studied using kinetic Monte Carlo simulations. The simulations were analyzed using reaction models and isoconversional analyses to extract constitutive coarsening laws, which confirm a coarsening exponent associated with classical surface diffusion. In addition, a rate equation is derived for the role of alloying dopants. It is found that only a few atomic percent is needed to stymie coarsening over experimentally relevant timescales, which has broad implications for the future design and tailoring of these materials.

Circumstellar Interaction in the Ultraviolet Spectra of SN 2023ixf 14–66 Days After Explosion

SN 2023ixf was discovered in M101 within a day of the explosion and rapidly classified as a Type II supernova with flash features. Here we present ultraviolet (UV) spectra obtained with the Hubble Space Telescope 14, 19, 24, and 66 days after the explosion. Interaction between the supernova ejecta and circumstellar material (CSM) is seen in the UV throughout our observations in the flux of the first three epochs and asymmetric Mg ii emission on day 66. We compare our observations to CMFGEN supernova models that include CSM interaction ( Ṁ<10−3 M ⊙ yr−1) and find that the power from CSM interaction is decreasing with time, from L sh ≈ 5 × 1042 erg s−1 to L sh ≈ 1 × 1040 erg s−1 between days 14 and 66. We examine the contribution of individual atomic species to the spectra on days 14 and 19, showing that the majority of the features are dominated by iron, nickel, magnesium, and chromium absorption in the ejecta. The UV spectral energy distribution of SN 2023ixf sits between that of supernovae, which show no definitive signs of CSM interaction, and those with persistent signatures assuming the same progenitor radius and metallicity. Finally, we show that the evolution and asymmetric shape of the Mg ii λ λ 2796, 2802 emission are not unique to SN 2023ixf. These observations add to the early measurements of dense, confined CSM interaction, tracing the mass-loss history of SN 2023ixf to ∼33 yr prior to the explosion and the density profile to a radius of ∼5.7 × 1015 cm. They show the relatively short evolution from a quiescent red supergiant wind to high mass loss.