Atomic Transition Research Articles

An integrated wavemeter based on fully-stabilized resonant electro-optic frequency comb

Optical frequency combs provide a powerful tool for precise measurement of the optical frequency, holding significant importance in fields such as spectroscopy, optical communication and optical clock. The frequency stability of the comb line determines the precision of the frequency measurement, but the delicate interplay between high precision, low power consumption and integration still needs to be optimized. To this aim, here we demonstrate a frequency measurement scheme based on a fully stabilized electro-optic comb, in which the pump laser frequency and repetition rate are independently locked to the atomic transition and microwave signal. The measurement precision of the demonstrated wavemeter can reach sub-kHz-level, and the parallel measurement of multiple wavelengths can be performed. Therefore, by combining the technical scheme reported here with advanced integrated functional devices, our system is expected to provide a feasible solution for chip-scale frequency precision measurement and reference.

Control of photon-photon interaction via a cavity.

Controlling the interaction between photons is one of the important technologies applied to quantum information processing at the few-photon level. We investigate the two-photon interaction via a Ξ-type atom, where one atomic transition is coupled to a one-dimensional waveguide, and the other transition is coupled to a cavity field. Whether the cavity is initially in the vacuum state or not, determines the effective configuration of the quantum emitter. When the cavity is in the vacuum state, only one bound state appears. We further found that the joint probability of transmitted photons oscillates with their spatial separation due to the coexistence of two bound states, if the cavity is in fock state |n〉 (n ≠ 0). With the incoming wave function consists entirely of plane waves, we present the exact out-state function that exhibit the bunching and antibunching behaviors. And, we discuss in detail with the behaviors of varying both the photon pair energy(E) and the energy difference between the two photons (Δ). Moreover, the spatial attraction and repulsion between the two transmitted photons can be controlled by the parameters of the cavity.

Rational design single-atom modified Zr2CO2 MXene as a promising catalyst for nitrogen reduction reaction

Renewable production of ammonia via the electrocatalytic nitrogen reduction reaction (NRR) is highly desirable. However, rational design of electrocatalysts with high promising activity under ambient conditions is a challenging subject. In this work, the stability, NRR activity and selectivity of single transition metal (TM, TM = Ti, V, Fe, Ni, Nb, Mo, Ru, and W), nonmetal B and N, and TM and N3 co-modification Zr2CO2 (named TM/Zr2CO2, B(N)/Zr2CO2, and TMN3/Zr2CO2, respectively) are investigated by density functional theory (DFT) calculations. The results revealed that single atom (both transition metal and nonmetal atoms) modification can greatly enhance the NRR catalytic activity and selectivity of original Zr2CO2, and different nonmetal doping concentration can deliver different NRR activity by adjust the interaction strength between doping atom and Zr atom. Among the studied materials, W/Zr2CO2 possesses the highest NRR performance via the distal pathway with the NRR overpotential (ηNRR) of 0.14 V, B/Zr2CO2 possesses the highest NRR performance (ηNRR = 0.26 V) and selectivity via the enzymatic pathway, and for the co-doped systems, RuN3/Zr2CO2 delivers the highest NRR activity with the corresponding ηNRR of 0.54 V. The crystal orbital Hamilton population (COHP), density of states, charge transfers, and work function (Φ) results indicated that the TM and nonmetal atoms can adjust the electronic properties of the Zr2CO2 surface to break the inertness of N2 and form the key intermediate *NNH or *N-*NH, and therefore enhance their NRR activity. The ab initio molecular dynamics (AIMD) simulation results suggested that the structures of the modified Zr2CO2 are dynamically stable at reaction temperature. These results indicated that the proposed surface modifications by W and nonmetal B are the effective approaches for achieving promising NRR electrocatalysts for N2 fixation.

Sensitive Detection of an Erbium Isotope in an Atomic Beam Using Cavity Ring-Down Spectroscopy.

We have applied cavity ring-down spectroscopy (CRDS) to the study of the 166Er isotope in an atomic beam. These measurements were realized with an external cavity diode laser tuned to the 400.9 nm atomic transition of erbium and a customized high-finesse ring-down optical cavity under vacuum. Erbium atomic beams of different number densities were generated in a tantalum foil micro-crucible within the cavity. Absorbance values of the 166Er isotope between 3 × 10-6 and 7 × 10-5 were measured with a best-case precision on the order of 10-6, which is remarkable when considering the extreme temperatures at which the measurements were conducted, and the short detection path which is characteristic of collimated atomic beams. Number densities of erbium atoms were inferred to be between 2 × 106 and 6 × 107 cm-3. This work demonstrates for the first time the ability of studying dilute atomic beams of refractory materials with high accuracy utilizing CRDS. In these initial studies, we used erbium as a model system, but we expect to extend the proposed approach to the measurement of isotopes of uranium and plutonium for nuclear non-proliferation applications.

Novel machine learning and differentiable programming techniques applied to the VIP-2 underground experiment

In this work, we present novel machine learning and differentiable programming enhanced calibration techniques used to improve the energy resolution of the Silicon Drift Detectors (SDDs) of the VIP-2 underground experiment at the Gran Sasso National Laboratory. We achieve for the first time a full width at half maximum in VIP-2 below 180 eV at 8 keV, improving around 10 eV on the previous state-of-the-art. SDDs energy resolution is a key parameter in the VIP-2 experiment, which is dedicated to searches for physics beyond the standard quantum theory, targeting Pauli exclusion principle violating atomic transitions. Additionally, we show that this method can correct for potential miscalibrations, requiring less fine-tuning with respect to standard methods.

Updated Reference Wavelengths for Si vii and Mg vii Lines in the 272–281 Å Range

New reference wavelengths for atomic transitions of Mg vii and Si vii in the 272–281 Å wavelength range are derived using measurements from the Extreme-ultraviolet Imaging Spectrometer (EIS) on board the Hinode spacecraft. Mg vii and Si vii are important ions for measuring plasma properties in the solar transition region at around 0.6 MK. The six Si vii wavelengths are 13–21 mÅ and 7–11 mÅ longer than the values in the NIST Atomic Spectra Database (ASD) and the compilations of B. Edlén, respectively. The four Mg vii wavelengths are shorter than the values in the ASD by 8–12 mÅ but show reasonable agreement with the Edlén values. The new wavelengths will lead to more accurate Doppler shift measurements from the EIS instrument and will be valuable for spectral disambiguation modeling for the upcoming Multi-Slit Solar Explorer mission.

An Executive Information System: Inherent Information and Functional Information

This review article deals with quantum biology, the new tool that helps traditional biology unravel some mysteries concerning life and living organisms on Earth. We use Einstein’s famous equation to explain how an unknown energy realm creates the material universe. We demonstrate how material existence precedes living existence and elucidate how non-living atoms transition to living molecules, Francis Crick’s faded dream that comes to reality. Finally, we expose the two types of Information available inside a cell to sustain life in living organisms and elaborate on a new formulation of the biogenesis theory.

Sub-Doppler dichroism as a useful tool in alkali atom hyperfine spectroscopy

Analytical modeling of the sub-Doppler dichroic atomic vapor laser lock error signal shows that the slope of this error signal could be of interest for the identification of transitions in alkali atom hyperfine spectroscopy. Among four D1 line transitions of alkali atoms, the slope sign of the sub-Doppler error signal is different only for the case when the Landé g-factor is negative for both the ground and excited states. The analytical model used, which includes all sublevel transitions, shows very good agreement with the experimental spectroscopy results. The use of this technique allows us to accurately characterize hyperfine transitions in alkali atoms without the need for advanced spectroscopic tools.

Photonic Crystal Surface Modes for Trapping and Waveguiding of Ultracold Atoms.

The design of a photonic system for the trapping and waveguiding of ultracold atoms far above a dielectric surface is proposed and analyzed. The system consists of an optical rib waveguide deposited on a planar one-dimensional photonic crystal, which sustains two wavelengths of photonic crystal surface modes tuned in the red and blue sides relative to the atomic transition of the neutral atom. The addition of a third blue-tuned wavelength to the system allows the neutral atoms to be stabilized in the lateral dimension above the rib waveguide. Trapping atoms at relatively large distances, more than 600 nm above the dielectric surface, allows to reduce the influence of Casimir-Polder forces in this system. The detailed design methodology and specifications of the photonic system are provided. The presented design can be employed in atomic chips and quantum sensors.

Advancing frequency locking: Modified FPGA-Guided direct modulation spectroscopy for laser stabilization

In this paper, we propose a cost-effective laser frequency locking scheme based on frequency modulation spectroscopy (FMS) for precision measurements and experiments in various fields. We demonstrate that by digitally modulating the detected signal frequency using a Field-Programmable-Gate-Array (FPGA) driven by a home-built lock-in and a proportional–integral–derivative (PID) control system, our system achieves higher precision, user-friendliness, and versatility. Our system generates a 20 V peak-to-peak amplified voltage to a piezo transducer (PZT), which enables a mode-hop free laser scan of approximately 2 ±0.2 GHz. We directly modulate the detected saturation absorption signal with a sinusoidal waveform, then demodulate it to obtain multiple zero crossing locking points on the D2 transition of Cs at 852.35 nm. We optimized the system for three commonly used atomic transitions and found that researchers can select any of the zero crossing peaks for frequency stabilization depending on their experimental requirements, we locked the laser at the crossover transition. We measured the long-time frequency fluctuation and power spectral density and found that the frequency fluctuation of the laser is much less than the natural line width of the D2 transition of Cs. Our results demonstrate that our laser frequency locking scheme is effective and practical for precision measurements and experiments in various fields.

Experimental atomic data of spectral lines – I. Cs, Ba, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Re, and Os in the 370–1000 nm interval

ABSTRACT Atomic data are fundamental for plasma diagnostics in laboratory and astrophysics through spectroscopy. These data are extensively present in data bases for light elements, however incomplete for high-mass atoms. This paper presents the results of systematic spectroscopy of 17 elements with high Z, expected to be produced in kilonova events generated by neutron star mergers, whose spectral lines are not yet fully identified in stellar spectra and fusion devices. Experimental data are from échelle high-resolution (λ/Δλ = 60 000) spectroscopy of hollow cathode lamps obtained with the Catania Astrophysical Observatory Spectropolarimeter covering the 3700–10 000 Å range in a single exposure. A total of about 7700 spectral lines with energy level classification not previously listed in the NIST, Kurucz, and VALD data bases are here reported for neutral and singly ionized atomic transitions. For the spectral lines of any species, we report the measured wavelengths and their relative intensities. If possible, we also estimate the transition probabilities under the assumptions of optically thin emission and electric-dipole transitions. These are converted into oscillator strengths ready to be inserted in astrophysical data bases for spectral synthesis.

Extrinsic electronic states to tune the luminescence and bonding nature of Cs2NaInCl6 double perovskite

Halide double perovskites have been extensively investigated in recent years as more stable and environmentally friendly materials with significant optoelectronic properties. Herein, we introduce Mn2+ ions in the Cs2NaInCl6 lattice to impart new electronic pathways to the otherwise weak optically active double perovskite for tuning its luminescent behaviour. X-ray diffraction, Raman, UV–visible, Photoluminescence (PL), and time–resolved PL (TRPL) spectroscopy are used to investigate the effect of Mn 2+ feed ratio on structural, vibrational, and optical properties. The chemical environment and surface morphology of the Mn2+ ions doped Cs2NaInCl6 double perovskite were investigated using X-ray photoelectron (XPS), energy dispersive X-ray (EDS) spectroscopies, and scanning electron microscopy. Results of the Rietveld refinement and Raman spectra divulge a decrease in In-Cl and Na-Cl bond length upon Mn2+ incorporation. The microstructure of the Cs2NaInCl6 double perovskite system was also studied using HRTEM analysis. UV–visible studies demonstrated a tremendous increase in absorption and a slight increase in band gap upon Mn2+ doping. PL and TRPL measurements of Mn2+: Cs2NaInCl6 discloses its red luminescence at 614 nm corresponding to the d-d atomic transition of Mn2+ with a long lifetime of 2.1 ms. Electron density investigations using maximum entropy method (MEM) demonstrate clear evolution of In-Cl and Na-Cl bonds from a highly ionic nature in pure Cs2NaInCl6 to strong covalent nature in Mn2+: Cs2NaInCl6 double perovskites. This affirms the simultaneous replacement of In, Na ions by Mn2+ to maintain charge neutrality in the compound and tune the electronic states of the Cs2NaInCl6 system.

Electromagnetically induced transparency and Autler-Towns effect in multi-level cascade type system in 133Cs

The probe field propagation through a twelve-level Ξ type atomic system, having two ground energy levels, four intermediate energy levels and six upper energy levels, is studied theoretically in presence of a control field connected from intermediate energy levels to upper energy levels of the transitions of 133Cs atom. Optical Bloch equations (OBEs) for the system are derived by density matrix formalism and are solved numerically under Doppler free and Doppler broadened conditions. The control field can simultaneously remain resonant or nearly resonant with certain hyperfine transitions and highly detuned with respect to other transitions. Under Doppler free condition the probe absorption curve shows multiple electromagnetically induced transparency peaks (EIT) formed within largely separated Autler-Towns (A-T) peaks. The A-T peaks are formed due to the dressing of the hyperfine transitions coupled by a highly detuned control field. The EIT windows get widened with increase in the Rabi frequency of the control field. The numerical result is compared with analytically solved reduced three-level Ξ type system. At room temperature the multiple transparency peaks get masked due to thermal averaging and an overall transparency like feature appears in the simulated Doppler broadened probe absorption curve.

Sensitivity improvement in the measurement of minor components by spatial confinement in fiber-optic laser-induced breakdown spectroscopy

Nuclear power overhaul can benefit from a fiber-optic laser-induced breakdown spectroscopy (FO-LIBS) setup for in situ composition measurements. Regarding FO-LIBS, the pulsed energy of the fiber-delivery laser is limited, and the spot profile received by the sample surface is distorted from a Gaussian to a flat-top distribution. Therefore, the induced plasma in FO-LIBS is characterized by weakened emission, shortened lifetime, and insufficient sampling of minor components compared with that of conventional LIBS. This could not meet the quantitative demands of the minor component with a concentration of 0.01 wt% or lower in structural steel. In this study, by modifying the mechanical structure of the front-end sensor, a space constraint condition can be created for plasma emission enhancement. By combining the optical diagnostics of fast photograph and shadowgraph, shockwave propagation and plasma expansion can be visualized synchronously. The reflected shockwave decelerates in the process of propagating towards the plasma, accompanied by morphological changes from the oblate cylinder to the hemisphere. It can be demonstrated that the plasma is constricted by the reflected shockwave associated with a significant increase in the plasma temperature and electron number density. The plate spacing determines the time delay of spectral enhancement and also determines the enhancement factor corresponding to the velocity attenuation of shockwave propagation over a long distance. The enhancement factor is found to be inversely proportional to the quadratic square of the propagation velocity of shockwave just after reflection, and shows an upward trend with increasing upper-level energy of atomic transitions. A maximum enhancement factor of ∼3.52 is realized with a time delay of 4 μs at a plate spacing of 3 mm, and trace components Mo, V, and Cu are newly recognized, which cannot be observed in conventional FO-LIBS. Meanwhile, the calibration of trace Cr and Mn suggests that the quantitative results using the sensor coupled with spatial confinement are comparable, and the limits of detection are reduced to 31 ppm and 475 ppm, respectively.

An atomic filter laser with a compact Voigt anomalous dispersion optical filter

The study of atomic physics has been greatly influenced by the development of high-stability diode lasers whose output corresponds to the atomic transition. Recently, an atomic filter laser “Faraday laser” shines on stage, owing to its great robustness to the fluctuation of the diode parameters and potentially higher tolerance to vibration. However, cost reduction and portability require the Faraday laser to have a more compact structure. Here, we report on the development of a promising atomic filter laser—a “Voigt laser”—using a Voigt anomalous dispersion optical filter (VADOF) as the frequency-selective element, which has a structural advantage in miniaturization. The influencing factors toward the VADOF are investigated in detail to produce a parameter set for the best performance of a Voigt laser. In this case, the Voigt laser has great robustness to the fluctuation in the diode current and temperature, where the wavelength fluctuation is ±0.5 pm with the variation of the diode parameters (diode current: 73–150 mA and diode temperature: 12–30 °C). In addition, the wavelength of the Voigt laser fluctuates about ± 0.5 pm for 48-h free-running operation and shows excellent reproducibility without manual adjustment. The laser system developed here provides a stable and reliable laser source for substantially improving existing technologies such as the atomic clock, electromagnetically induced transparency, and laser cooling of atoms.

Self-healing of fractured diamond.

Materials that possess the ability to self-heal cracks at room temperature, akin to living organisms, are highly sought after. However, achieving crack self-healing in inorganic materials, particularly with covalent bonds, presents a great challenge and often necessitates high temperatures and considerable atomic diffusion. Here we conducted a quantitative evaluation of the room-temperature self-healing behaviour of a fractured nanotwinned diamond composite, revealing that the self-healing properties of the composite stem from both the formation of nanoscale diamond osteoblasts comprising sp2- and sp3-hybridized carbon atoms at the fractured surfaces, and the atomic interaction transition from repulsion to attraction when the two fractured surfaces come into close proximity. The self-healing process resulted in a remarkable recovery of approximately 34% in tensile strength for the nanotwinned diamond composite. This discovery sheds light on the self-healing capability of nanostructured diamond, offering valuable insights for future research endeavours aimed at enhancing the toughness and durability of brittle ceramic materials.

Frequency tunable single photon diode based on giant atom coupling to a waveguide.

The single photon scattering properties in a waveguide coupling to a giant atom with a three-level system are investigated theoretically. One of the transitions of the giant atom couples to the waveguide at two points while the other one is driven by a classical field. Using the analytical expressions of the single photon scattering amplitudes, the conditions for realizing perfect single photon nonreciprocal scattering are discussed in both Markovian regime and non-Markovian regime. In the Markovian regime, the perfect non-reciprocity can be realized by adjusting the external classical field, the energy dissipation of the giant atom, the phase difference between the two coupling strengths and the accumulated phase resulting from the photon propagating between the two coupling points. In the non-Markovian regime, the non-reciprocal scattering phenomenon becomes more abundant due to the time delay. However, the analytical results show that the perfect non-reciprocity can still be achieved. When the incident photon is resonant with the giant atom, the nonreciprocity can be switched by controlling the classical field. For the non-resonant single photon, one can adjust the Rabi frequency of the classical field to obtain the perfect non-reciprocal single photon transmission. Our work provides a manner to realize a frequency tunable single photon diode.

Competition between Zeeman and hyperfine pumping in thermal atomic vapor

We present ab initio reduced rate equation models to study the interplay of Zeeman and hyperfine pumping, which determines the Doppler-broadened absorption spectra of an arbitrarily polarized probe laser, in thermal atomic vapor. Our simple models (with maximum seven levels) accurately predict the dependence of probe absorption on its polarization for the 87Rb D2 line (residual error <2%) without any fitting parameters, while being ∼100× less computational resource intensive as compared to numerically complex full multi-level models that treat all (up to 23) the magnetic (m F ) sub-levels present in the system individually. We demonstrate that either Zeeman or hyperfine pumping dominates depending on whether the atomic transitions being probed are primarily closed or open.

Algebraic relations from finite-nuclear-mass effects to test atomic transition rates

Algebraic relations from finite-nuclear-mass effects to test atomic transition rates

Homogeneous Nanostructured VO2@SiO2 as an Anti-Reflecting Layer in the Visible/Near Infrared Wavelength.

Low reflectivity is of great significance to photoelectric devices, optical displays, solar cells, photocatalysis and other fields. In this paper, vanadium oxide is deposited on pattern SiO2 via atomic layer deposition and then annealed to characterize and analyze the anti-reflection effect. Scanning electron microscope (SEM) images indicate that the as-deposited VOx film has the advantages of uniformity and controllability. After annealing treatment, the VO2@pattern SiO2 has fewer crevices compared with VO2 on the accompanied planar SiO2 substrate. Raman results show that there is tiny homogeneous stress in the VO2 deposited on pattern SiO2, which dilutes the shrinkage behavior of the crystallization process. The optical reflection spectra indicate that the as-deposited VOx@pattern SiO2 has an anti-reflection effect due to the combined mechanism of the trapping effect and the effective medium theory. After annealing treatment, the weighted average reflectance diminished to 1.46% in the visible near-infrared wavelength range of 650-1355 nm, in which the absolute reflectance is less than 2%. Due to the multiple scattering effect caused by the tiny cracks generated through annealing, the anti-reflection effect of VO2@pattern SiO2 is superior to that of VOx@pattern SiO2. The ultra-low reflection frequency domain amounts to 705 nm, and the lowest absolute reflectance emerges at 1000 nm with an astonishing value of 0.86%. The prepared anti-reflective materials have significant application prospects in the field of intelligent optoelectronic devices due to the controllability of atomic layer deposition (ALD) and phase transition characteristics of VO2.