Search Results (60)

The single-step Rydberg excitation of cesium atoms requires a 319 nm ultraviolet laser with a narrow laser linewidth, high frequency stability, and high output power. To meet these requirements, in this work, we construct a high-power, single-frequency UV laser system at this wavelength. In this system, the frequency stabilization of the 1560.492 nm seed laser is critical to the performance of the ultraviolet laser. We employ nonlinear frequency conversion technology, the 1560.492 nm laser is frequency-doubled to 780.246 nm via a single pass through a PPLN crystal, and function integration is realized based on the modular parameter adjustment interface provided by the PyRPL software. Subsequently, the 1560.492 nm laser is stabilized to the $D_2$ hyperfine transition line of Rb-87 atoms using polarization spectroscopy (PS) and radio-frequency-modulated saturation absorption spectroscopy (RF-SAS). A comparative study of these two techniques shows that RF-SAS achieves superior stabilization performance, with the residual frequency fluctuation of the frequency-doubled laser being 1.07 MHz over 30 min. According to frequency doubling theory, the actual residual frequency fluctuation of the 1560.492 nm fundamental-frequency laser can be calculated as 0.535 MHz. Compared with our earlier scheme that utilized an ultra-low-expansion (ULE) optical cavity as a frequency reference, the present scheme eliminates the long-term drift induced by environmental factors. In contrast to frequency stabilization relying on discrete instruments, this integrated scheme significantly reduces the cost, simplifies the system architecture, saves space, and greatly enhances the flexibility and controllability of the system. It therefore provides a reliable and cost-effective solution to ensure the portability and practicability of high-performance UV laser sources. This high-precision frequency stabilization scheme directly guarantees the performance of the 319 nm UV laser, suppressing its linewidth below 10 kHz. Thus, it fully meets the stringent laser linewidth and frequency stability requirements for the single-step Rydberg excitation of cesium atoms and provides a reliable light source foundation for subsequent precision spectroscopic measurements. Full article

In PAC spectroscopy, hyperfine interactions of a radioactive probe nucleus with its surroundings are measured, providing information about the local atomic structure and dynamics at the probe site. In the so-called fast reorientation time regime for fluctuating nuclear quadrupole interactions (NQIs), the PAC signal is an exponentially decaying function, with decay constant λ depending on both the hyperfine interaction and dynamics. For a molecular system in solution, dynamics may originate from Brownian molecular tumbling (rotational diffusion) with rotational correlation time τ_c and from local dynamics at the probe site, occurring at a characteristic time scale τ_loc. The τ_c and the τ_loc cannot be discriminated in a single PAC spectrum; however, assuming that they scale differently with viscosity and temperature, a series of experiments in which these parameters are varied may allow for discrimination of τ_c and the τ_loc. Three models are presented for the effect of dynamics on the PAC signal: (1) the Stokes–Einstein–Debye model with linear scaling of λ with viscosity ξ; (2) a more general model presenting a power law scaling of λ with (ξ/ξ₀)ⁿ; and (3) a model that includes rotational and local dynamics leading to an expression for λ that scales with ξ/(ξ + c), where c is a constant that depends on temperature, molecular volume, and τ_loc. These models may serve as different approaches to analyze PAC data and their dependence on temperature and solvent viscosity in the fast reorientation time regime, and they can be applied to design experiments for optimal discrimination of global rotational diffusion and local dynamics at the probe site. Full article

This paper investigates the dynamics of quantum and classical geometric correlations in the hyperfine structure of the hydrogen atom under pure dephasing noise, focusing on the interplay between entangled initial states and environmental effects. We employ the Lindblad master equation to model dephasing, deriving differential equations for the density matrix elements to capture the evolution of the system. The study explores various entangled initial states, characterized by parameters $a_1$, $a_2$, and $a_3$, and their impact on correlation dynamics under different dephasing rates $\Gamma$. A trace distance approach is utilized to quantify classical and quantum geometric correlations, offering comparative insights into their behavior. Numerical analysis reveals a transition point where classical and quantum correlations equalize, followed by distinct decay and stabilization phases, influenced by initial coherence along the z-axis. Our results reveal a universal sudden transition from classical to quantum decoherence, consistent with observations in other open quantum systems. They highlight how initial state preparation and dephasing strength critically influence the stability of quantum and classical correlations, with direct implications for quantum metrology and the development of noise-resilient quantum technologies. By focusing on the hyperfine structure of hydrogen, this study addresses a timely and relevant problem, bridging fundamental quantum theory with experimentally accessible atomic systems and emerging quantum applications. Full article

This article introduces the main characteristics of PyMossFit, a software for Mössbauer spectra fitting. It is explained how each aspect of the code works. Based on the Lmfit Python package, it is a robust data fitting tool. Designed to run through Jupyter Notebook in the Google Colab cloud, it also allows one to work via multiple devices and operating systems. In addition, it allows the fitting procedure to be performed collaboratively among researchers. The software performs the folding of raw data with a discrete Fourier transform. Data smoothing is available with the use of a Savitzky–Golay algorithm. Moreover, a K-nearest neighbor algorithm enables users to determine the present phases by matching the correlations of hyperfine parameters from a local database. Full article

Solid-state spin centers are at the forefront of developing advanced quantum technologies, engaging in applications of sensing, communication and computing. A semiconductor host matrix compatible with existing silicon technology provides a robust platform for holding spin defects and an opportunity for external manipulation. In this article, negatively charged nitrogen-vacancy (NV) centers in the hexagonal hh position in a 6H polytype silicon carbide crystal was studied using high-frequency (94 GHz) electron paramagnetic (EPR) and electron nuclear double resonances (ENDOR) spectroscopy. Experimentally determined values of hyperfine and quadrupole interactions of ¹⁴N were compared with the values obtained for the centers in NV_k2k1 positions. The distribution of spin density of the defect within a supercell of the SiC crystal lattice was calculated using the density functional theory approach. The theoretical estimation of electron-nuclear interaction constants turned out to be in close agreement with the experimental values, which allows us to refine the microscopic model of a point defect. The temperature dependence of the spin Hamiltonian values (δA/δT ≅ 180 Hz/K) was studied with the possibility of observing the ¹⁴N NMR signal at room temperature. The fundamental knowledge gained about interactions’ parameters’ behavior lays the foundation for the creation of promising quantum platforms. Full article

In this work, we investigate the quantum coherence and purity in hydrogen atoms under dissipative dynamics, with a focus on the hyperfine structure states arising from the electron–proton spin interaction. Using the Lindblad master equation, we model the time evolution of the density matrix of the system, incorporating both the unitary dynamics driven by the hyperfine Hamiltonian and the dissipative effects due to environmental interactions. Quantum coherence is quantified using the $L_1$ norm and relative entropy measures, while purity is assessed via von Neumann entropy, for initial states, including a maximally entangled Bell state and a separable state. Our results reveal distinct dynamics: for the Bell states, both coherence and purity decay exponentially with a rate proportional to the dissipation parameter, whereas for a kind of separable state, coherence exhibits oscillatory behavior modulated via the hyperfine coupling constant, superimposed on an exponential decay, and accompanied by a steady increase in entropy. Higher dissipation rates accelerate the loss of coherence and the growth of von Neumann entropy, underscoring the environment’s role in suppressing quantum superposition and driving the system towards mixed states. These findings enhance our understanding of coherence and purity preservation in atomic systems and offer insights for quantum information applications where robustness against dissipation is critical. Full article

Avoided level crossing muon spin resonance (ALC-$\mu$SR) is used to characterize muoniated free radicals. These radicals are used as probes of the local environment and reorientational motion of specific components in complex systems. The parameter that provides information about the anisotropic motion is the motionally-averaged muon dipolar-hyperfine coupling constant ($⟨D_{\mu }^{\Vert }⟩$). The ALC-$\mu$SR spectra of muoniated radicals in anisotropic environments frequently have Lorentzian-like ${\mathsf{\Delta }}_1$ resonances, which makes it challenging to extract $⟨D_{\mu }^{\Vert }⟩$. In this paper, we derive a means to estimate$|⟨D_{\mu }^{\Vert }⟩|$ from ALC-$\mu$SR spectra with Lorentzian-like resonances by measuring the amplitude, width, and position of the ${\mathsf{\Delta }}_1$ resonance and the amplitude, width, and position of a ${\mathsf{\Delta }}_0$ resonance. Numerical simulations were used to test this relationship for radicals with a wide range of muon and proton hyperfine parameters. We use this methodology to determine $|⟨D_{\mu }^{\Vert }⟩|$ for the Mu adducts of the cosurfactant 2-phenylethanol in ${\mathrm{C}}_{12}$E₄ bilayers. From this we determined the amplitude of the anisotropic reorientational motion of the cosurfactant. Full article

The mass $m_{{\mu }^{-}}$ of the negative muon is one of the parameters of the elementary particle Standard Model and it allows us to verify the CPT (charge–parity–time) symmetry theorem by comparing $m_{{\mu }^{-}}$ value with the mass $m_{{\mu }^{+}}$ of the positive muon. However, the experimental determination precision of $m_{{\mu }^{-}}$ is $3.1\mathrm{ppm}$, which is an order of magnitude lower than the determination precision of $m_{{\mu }^{+}}$ at $120\mathrm{ppb}$. The authors aim to determine $m_{{\mu }^{-}}$ and the magnetic moment ${\mu }_{{\mu }^{-}}$ with a precision of $\mathcal{O}\left(10\mathrm{ppb}\right)$ through spectroscopy of the hyperfine structure (HFS) of muonic helium-4 atom ${(}^4\mathrm{He}{\mu }^{-}{e}^{-})$ under high magnetic fields. ${}^4\mathrm{He}{\mu }^{-}{e}^{-}$ is an exotic atom where one of the two electrons of the ${}^4\mathrm{He}$ atom is replaced by a negative muon. To achieve the goal, it is necessary to determine the HFS of ${}^4\mathrm{He}{\mu }^{-}{e}^{-}$ with a precision of $\mathcal{O}\left(1\mathrm{ppb}\right)$. This paper describes the determination procedure of the HFS of ${}^4\mathrm{He}{\mu }^{-}{e}^{-}$ in weak magnetic fields reported recently, and the work towards achieving the goal of higher precision measurement. Full article

The investigation and clarification of the properties of surface-functionalized superparamagnetic nanoparticles in a biological environment are key challenges prior to their medical applications. In the present work, electron paramagnetic resonance spectroscopy (EPR) combined with the spin labeling technique was utilized to better understand the behavior of nitroxides attached to magnetite nanoparticles dispersed in body fluid. EPR spectra of spin-labeled, silane-coated Fe₃O₄ nanoparticles in human serum and whole blood were recorded and analyzed for both room- and low-temperature values. In all cases, the obtained EPR signal consisted of a broad line from magnetite cores and a characteristic signal from the attached 4-Amino-2,2,6,6-tetramethylpiperidine-1-oxyl (4-amino-TEMPO). Even for liquid samples, the anisotropic components of magnetic tensors did not fully average out, which was reflected in the differences in the intensity of three narrow hyperfine lines from nitroxide. At 230 K the irregular slow-motion signal from the attached radical was also simulated using the EasySpin toolbox, which allowed to determine the parameters related to magnetic tensors and the dynamics of the spin label. The study showed that the anisotropy of the motion of the spin label 4-amino-TEMPO reflects its interactions with the surrounding medium and the manner of the attachment of the nitroxide to the surface of nanoparticles. Full article

Here, we report the results of a Mössbauer study on hyperfine electrical and magnetic interactions in quadruple perovskite BiMn₇O₁₂ doped with ⁵⁷Fe probes. Measurements were performed in the temperature range of 10 K < T < 670 K, wherein BiMn_6.96⁵⁷Fe_0.04O₁₂ undergoes a cascade of structural (T₁ ≈ 590 K, T₂ ≈ 442 K, and T₃ ≈ 240 K) and magnetic (T_N1 ≈ 57 K, T_N2 ≈ 50 K, and T_N3 ≈ 24 K) phase transitions. The analysis of the electric field gradient (EFG) parameters, including the dipole contribution from Bi³⁺ ions, confirmed the presence of the local dipole moments p_Bi, which are randomly oriented in the paraelectric cubic phase (T > T₁). The unusual behavior of the parameters of hyperfine interactions between T₁ and T₂ was attributed to the dynamic Jahn–Teller effect that leads to the softening of the orbital mode of Mn³⁺ ions. The parameters of the hyperfine interactions of ⁵⁷Fe in the phases with non-zero spontaneous electrical polarization (P_s), including the P1 ↔ Im transition at T₃, were analyzed. On the basis of the structural data and the quadrupole splitting Δ(T) derived from the ⁵⁷Fe Mössbauer spectra, the algorithm, based on the Born effective charge model, is proposed to describe P_s(T) dependence. The P_s(T) dependence around the Im ↔ I2/m phase transition at T₂ is analyzed using the effective field approach. Possible reasons for the complex relaxation behavior of the spectra in the magnetically ordered states (T < T_N1) are also discussed. Full article

Nuclear Magnetic Resonance (NMR) spectroscopy is the ideal tool to address the structure, reactivity and dynamics of both inorganic and biological substances. The knowledge of nuclear spin interaction and spin dynamics is increasingly consolidated, and this allows for tailoring pulse sequences. When dealing with paramagnetic systems, several decades of research have led to the development of rule-of-the-thumb criteria for optimizing the experiments, allowing for the detection of nuclei that are in very close proximity to the metal center. In turn, the observation of these systems, coupled with the development of robust and accessible quantum chemical methods, is promising to provide a link between the spectra and the structural features through the interpretation of the electronic structure. In this review, we list the challenges encountered and propose solutions for dealing with paramagnetic systems with the greatest satisfaction. In our intentions, this is a practical toolkit for optimizing acquisition and processing parameters for routine experiments aimed at detecting signals influenced by the hyperfine interaction. The implications of paramagnetic shift and line broadening are examined. With this endeavor, we wish to encourage non-expert users to consider the application of paramagnetic NMR to their systems. Full article

The molecular structure of a van der Waals-bonded complex involving 2,6-di-tert-butylphenol and a single argon atom has been determined through rotational spectroscopy. The experimentally derived structural parameters were compared to the outcomes of quantum chemical calculations that can accurately account for dispersive interactions in the cluster. The findings revealed a π-bound configuration for the complex, with the argon atom engaging the aromatic ring. The microwave spectrum reveals both fine and hyperfine tunneling components. The main spectral doubling is evident as two distinct clusters of lines, with an approximate separation of 179 MHz, attributed to the torsional motion associated with the hydroxyl group. Additionally, each component of this doublet further splits into three components, each with separations measuring less than 1 MHz. Investigation into intramolecular dynamics using a one-dimensional flexible model suggests that the main tunneling phenomenon originates from equivalent positions of the hydroxyl group. A double-minimum potential function with a barrier of 1000 (100) cm⁻¹ effectively describes this extensive amplitude motion. However, the three-fold fine structure, potentially linked to internal motions within the tert-butyl group, requires additional scrutiny for a comprehensive understanding. Full article

In this study, we give a thorough evaluation of the structural, magnetic, and magnetocaloric properties in iron-rich PrFe${}_{11}$Ti intermetallic alloy with ThMn${}_{12}$-type structure using a combination of experimental and theoretical analysis. X-ray diffraction coupled with Rietveld refinement was used to characterize the structure, which revealed a unique tetragonal crystal structure with $I4/mmm$ space group. The $8i$ site was identified as the preferred site for the Ti atom. This finding was confirmed by various techniques, including XRD, DFT, and Mössbauer spectrometry. Magnetic properties were studied through intrinsic magnetic measurements and magnetocaloric effect analysis. Mössbauer spectroscopy was employed to probe the local magnetic environment and for further characterization of the material’s magnetic properties. The experimental results were complemented by theoretical calculations based on density functional theory (DFT). A promising magnetocaloric effect is observed, with a significant maximum magnetic entropy ($-\Delta S_M^{\max }$ = 2.5 J·kg${}^{-1}$·K${}^{-1}$) and a relative cooling power about 70 J·kg${}^{-1}$ under low magnetic field change ${\mu }_0\Delta H$ = 1.5 T. Overall, our results provide a deeper understanding of the structural and magnetic properties of the material under study and demonstrate the effectiveness of the combined experimental and theoretical approach in the investigation of complex materials. The insights gained from this study could have implications for the development of advanced magnetic materials with enhanced properties for potential magnetic applications. Full article

Magnetic Functional Nanomaterials Co_1−yZn_yRE_xFe_2−xO₄ (RE (rare-earth) = La,Sm,Gd) were prepared using the sol–gel combustion method. XRD characterization confirms that the ferrite samples we synthesized are single-phase cubic structures. The variation in the average crystalline size and lattice parameter is related to RE ion doping. The Mössbauer spectra of CoRE_xFe_2−xO₄ are two sets of magnetic six-wire peaks that indicate the ferrimagnetic behavior of the sample. The calcination temperature greatly influences the absorption area of Mössbauer for CoFe₂O₄, indicating that the calcination temperature affects the iron ion content at the octahedral B and tetrahedral A sites. Additionally, scanning electron microscopy measurements of the substituted specimens reveal that the ferrite powders are nanoparticles. With an increase in RE ions, the coercivity increases, and the saturation magnetization changes obviously. The XRD characterization of Co_0.7Zn_0.3La_xFe_2−xO₄ shows that the main crystalline phase of the sample is the cubic spinel structure phase, and there are fewer secondary crystalline phases. The lattice parameter tends to decrease with the substitution of La³⁺ ions. The average grain size decreased significantly with the increase in La content. From ferrimagnetic state transition to relaxation behavior, the hyperfine magnetic field decreases in La concentration by room temperature Mössbauer spectra. With the substitution of La³⁺ ions, both the saturation magnetization and coercivity of the samples were reduced, and the coercivity of all samples was lower. Full article

For the realization of an optical nuclear clock, the first isomeric excited state of thorium-229 (^229mTh) is currently the only candidate due to its exceptionally low-lying excitation energy ($8.338\pm 0.024$ eV). Such a nuclear clock holds promise not only to be a very precise metrological device but also to extend the knowledge of fundamental physics studies, such as dark matter research or variations in fundamental constants. Considerable progress was achieved in recent years in characterizing ^229mTh from its first direct identification in 2016 to the only recent observation of the long-sought-after radiative decay channel. So far, nuclear resonance as the crucial parameter of a nuclear frequency standard has not yet been determined with laser-spectroscopic precision. To determine another yet unknown basic property of the thorium isomer and to further specify the linewidth of its ground-state transition, a measurement of the ionic lifetime of the isomer is in preparation. Theory and experimental investigations predict the lifetime to be 10³–10⁴ s. To precisely target this property using hyperfine structure spectroscopy, an experimental setup is currently being commissioned at LMU Munich. It is based on a cryogenic Paul trap providing long-enough storage times for ^229mTh ions, that will be sympathetically cooled with ⁸⁸Sr⁺. This article presents a concept for an ionic lifetime measurement and discusses the laser-optical part of a setup specifically developed for this purpose. Full article