Splitting Of Spectral Lines Research Articles

XIAM-NQ: Implementation of exact quadrupole coupling

In rotational spectroscopy, the nuclear quadrupole coupling of spins to the rotation of a molecule frequently leads to significant hyperfine splittings of spectral lines, complicating spectral analysis. This complexity increases further when internal rotation fine splittings, particularly from methyl groups, are also present. The XIAM program, recognized in the community for its ability to address methyl internal rotation and handle nuclear quadrupole coupling for a single nucleus, while neglecting off-diagonal matrix elements in the quantum number J, has now been enhanced. The updated version, XIAM-NQ, includes the previously omitted matrix elements, enabling an exact treatment of quadrupole coupling. This new version offers precise spectral fits with minimal fitting times, even for molecules containing bromine and iodine nuclei. The effectiveness of XIAM-NQ is demonstrated on o-halotoluenes and m-chlorotoluene.

Sensitivity of motional Stark effect on different beam energy components for radial electric field measurements in tokamak plasmas.

Measurement of the internal magnetic field is crucial for determining the equilibrium, stability, and current density of a plasma in a tokamak. A motional Stark Effect (MSE) diagnostic was developed to provide a measurement of the internal magnetic field in tokamaks by analyzing the emission from the interaction of the plasma particle with an injected neutral beam. The Stark effect causes the shifting and splitting of deuterium spectral lines due to the Lorentz electric field. However, it is difficult to accurately measure the internal magnetic field components since the radial electric field inherently formed inside the plasma is mixed with the Lorentz field. Under the circumstances in the Korea Superconducting Tokamak Advanced Research (KSTAR) device, one possible approach is to derive a radial electric field by measuring and comparing the polarization angles from the full and half-energy components of the neutral beam. To utilize the polychromatic MSE diagnostics in KSTAR, the half-energy component wavelength bands according to various magnetic field and beam energy combinations have been calculated, and the filter combinations required for those measurements have been selected. The Stokes-filter model used to evaluate the effect of multiple-ion-source neutral beam injection on the MSE measurements has been extended to infer the sensitivity of this approach to take the non-ideal bandpass filter effects into account.

High-resolution spectroscopy of LaAlO3-Pr3+ pseudo-cubic perovskite single crystals: Crystal-field parameters, hyperfine and deformation splittings

We report high-resolution measurements and analysis of the optical transmission and emission spectra of a concentration series of La(1-x)PrxAlO3 (x = 10−3, 9 ⋅ 10−3, and 2 ⋅ 10−2) single crystals in a wide frequency range ((2-27) ⋅ 103 cm−1) at temperatures 5–300 K, below the structural phase transition from the cubic Pm3‾m to the rhombohedral R3‾c phase. Pr3+ ions substitute for La3+ ions at sites with point symmetry D3. All recorded spectral lines are assigned to specific initial and final crystal-field (CF) energy levels, the scheme of CF levels is constructed and described by an appropriate set of CF parameters. The structural phase transition is accompanied by shear strains and the formation of ferroelastic twin domains of four types compressed along one of the four C3 axes in the parent cubic crystal lattice. Specific features of the measured spectra, namely, anomalous broadening of spectral lines and doublet structure of some lines corresponding to transitions between CF singlets and doublets, are considered as a result of interaction of 4f electrons with the field of random shear deformations competing at the boundaries of twin domains. Modeling of the observed line shapes was performed taking into account both hyperfine interactions and random lattice strains, as well as the effect of temperature. The width (6.6 ± 0.7)⋅10− 4 of the introduced two-dimensional distribution function of random strains was found from a comparison of simulated and measured profiles of the split spectral lines. The results of this work can be applied for quantitative assessment of crystal quality.

Spectral characterization of elemental emissions, experimental insights and theoretical evaluation

This experimental study delves into the spectral analysis of five discrete spectral lamps, namely helium, sodium, mercury, cadmium and zinc, utilizing a suite of scientific instrumentation including an optical spectrometer with converging lenses and a diffraction grating. The primary objective is to determine the wavelengths corresponding to visible spectral lines emitted by these lamps. Calibration of the spectrometer with the helium lamp facilitated the derivation of the diffraction grating constant. Subsequent measurements of diffraction angles allowed for the computation of experimental wavelengths, which were then compared with theoretical values. Analysis revealed slight discrepancies between experimental and theoretical values, likely attributed to systematic errors such as extraneous light sources and parallax errors in angle measurements. Furthermore, examination of spectral line splitting demonstrated the removal of degeneracy within specified energy levels, resulting in the observation of distinct spectral components. Overall, this study underscores the significance of meticulous experimental techniques in the elucidation of fundamental physical phenomena and highlights the interplay between theory and observation in spectral analysis.

Positive Trions in InP/ZnSe/ZnS Colloidal Nanocrystals.

InP-based colloidal nanocrystals are being developed as an alternative to cadmium-based materials. However, their optical properties have not been widely studied. In this paper, the fundamental magneto-optical properties of InP/ZnSe/ZnS nanocrystals are investigated at cryogenic temperatures. Ensemble measurements using two-photon excitation spectroscopy revealed the band-edge hole state to have 1Sh symmetry, resolving some controversy on this issue. Single nanocrystal microphotoluminescence measurements provided increased spectral resolution that facilitated direct detection of the lowest energy confined acoustic phonon mode at 0.9 meV, which is several times smaller than the previously reported values for similar nanocrystals. Zeeman splitting of narrow spectral lines in a magnetic field indicated a bright trion emission. A simple trion model was used to identify a positive trion charge. Furthermore, the Zeeman split spectra allowed the direct measurement of both the electron and hole g-factors, which match existing theoretical predictions.

Testing pulsation diagnostics in the rapidly oscillating magnetic Ap star γ Equ using near-infrared CRIRES+ observations

Context. Pulsations of rapidly oscillating Ap stars and their interaction with the stellar magnetic field have not been studied in the near-infrared (near-IR) region despite the benefits these observations offer compared to visual wavelengths. The main advantage of the near-IR is the quadratic dependence of the Zeeman effect on the wavelength, as opposed to the linear dependence of the Doppler effect. Aims. To test pulsation diagnostics of roAp stars in the near-IR, we aim to investigate the pulsation behaviour of one of the brightest magnetic roAp stars, γ Equ, which possesses a strong surface magnetic field of the order of several kilogauss and exhibits magnetically split spectral lines in its spectra. Methods. Two magnetically split spectral lines belonging to different elements, the triplet Fe I at 1563.63 nm and the pseudo-doublet Ce III at 1629.2 nm, were recorded with CRIRES+ over about one hour in the H band with the aim of understanding the character of the line profile variability and the pulsation behaviour of the magnetic field modulus. Results. The profile shapes of both studied magnetically split spectral lines vary in a rather complex manner probably due to a significant decrease in the strength of the longitudinal field component and an increase in the strength of the transverse field components over the last decade. A mean magnetic field modulus of 3.9 kG was determined for the Zeeman triplet Fe I at 1563.63 nm, whereas for the pseudo-doublet Ce III at 1629.2 nm we observe a much lower value of only about 2.9 kG. For comparison, a mean field modulus of 3.4kG was determined using the Zeeman doublet Fe II at 6249.25 in optical PEPSI spectra recorded just about two weeks before the CRIRES+ observations. Different effects that may lead to the differences in the field modulus values are discussed. Our measurements of the mean magnetic field modulus using the line profiles recorded in different pulsational phase bins suggest a field modulus variability of 32 G for the Zeeman triplet Fe I at 1563.63 nm and 102 G for the pseudo-doublet Ce III at 1629.2 nm.

The Accuracy of Frequency Estimation of Structure Vibration under Ambient Excitation: Problems, Causes, and Methods

Accurate identification of building structure frequencies forms the basis for damage detection. The structural dynamic response signal, under ambient excitation, can be transformed into a superposition of multiple single-frequency exponentially damped sinusoids combined with random white noise. However, the peak power spectrum of the response signal tends to exhibit line splitting, compromising the precision of frequency identification. This study examines the accuracy characteristics of the single-frequency free damping vibration signal (SFFDVS) and derives the Cramer–Rao lower bound for the frequency estimator. It thoroughly analyzes the factors influencing the accuracy of SFFDVS frequency identification. The study reveals that the primary cause of spectral line splitting is the random delay inherent in SFFDVS. Based on the maximum likelihood method (MLM), this research introduces the MLM algorithm for SFFDVS and provides a simulation analysis. The findings indicate that the MLM estimation algorithm for frequency parameters effectively addresses spectral line splitting and offers robust noise resistance and recognition accuracy.

The effects of gravitational waves on a hydrogen atom

We investigate the influence of gravitational waves on a freely falling hydrogen atom by analyzing the dynamics of the bound electron described by the Dirac equation in the curved spacetime of a gravitational wave. From this, we derive the corresponding Dirac Hamiltonian in the local inertial frame of the atom, assuming gravitational waves are described by the linearized theory of general relativity. To maintain meaningful physical interpretations while obtaining a non-relativistic description, we employ the Foldy–Wouthuysen transformation. Through the analysis of resulting interaction terms and comparison with flat spacetime counterparts, valuable insights into the effects of gravitational waves (GWs) on the hydrogen atom are gained. Additionally, we explore selection rules governing the coupling between GWs and the atom and utilize first-order perturbation theory to quantify the induced energy shifts and spectral line splitting. This investigation contributes to our understanding of the interplay between quantum systems and gravitational waves, which could lead to alternative method of GWs indirect detection. However, measuring such tiny energy shifts would require a telescope with very high spectral resolution.

The State of Water in "Ionic Liquid [bmim]Cl/AlCl3/H2O" Systems.

The unique physical and chemical properties of ionic liquids (ILs) determine their numerous applications in "green" chemistry and material science. Recently, systems based on ILs have been considered to be promising for use in a new generation of electrochemical devices. The results of a nuclear magnetic resonance (NMR) study of the microstructure of 1-butyl-3-methylimidazolium chloride (IL)/water mixtures in the presence of Al3+ cations are presented. For the first time, the splitting of spectral lines of water in such systems has been recorded. Comparing the 1H and 27Al NMR data, we have detected the existence of different solvate complexes of Al3+ with Cl- and estimated the characteristic times of exchange processes. For the system under study, a model of the Al3+ cation environment and its evolution with temperature and water content has been described. Quantum-chemical calculations have been performed to substantiate the model.

Investigating exceptional points in dark-bright mode-coupled plasmonic systems.

Exceptional points (EPs) of non-Hermitian systems are gaining more and more attention due to their important applications in unidirectional transmitters, sensors, etc. However, theoretical studies on EPs of reflection, transmission, and absorption spectra are less available. In this paper, in the dark-bright mode-coupled plasmonic systems, the variations of EPs of reflection, transmission, and absorption spectra are numerically investigated using temporal coupled-mode theory, and an assumption is given using the representation transformation theory. The intermediate representation (IR) is firstly proposed and related to the reflection spectrum, while the normal representation (NR) is associated with the absorption spectrum. In the region far from EPs, the IR (or NR) describes the reflection (or absorption) spectrum well. Near EPs, modified formulas similar to the representation transformation theory are given. In order to verify the correctness of the assumption, two metasurfaces are designed. And the simulation results are in good agreement with the assumption and it is found in the near-infrared and visible-light band that the absorption loss of the dark mode is linearly related to the EPs of reflection, transmission, and absorption spectra, while the radiation loss of the bright mode is only linearly related to the EPs of the absorption spectrum. These laws can help to manipulate the splitting of spectral lines for reflection, transmission, and absorption by adjusting the radiation loss and absorption loss of bright mode, the absorption loss of dark mode, and the coupling coefficients between two resonant modes. This research provides a guiding scheme for the design of micro and nano photonics devices.

A DZ white dwarf with a 30 MG magnetic field

ABSTRACTMagnetic white dwarfs with field strengths below 10 MG are easy to recognize since the Zeeman splitting of spectral lines appears proportional to the magnetic field strength. For fields ≳100 MG, however, transition wavelengths become chaotic, requiring quantum-chemical predictions of wavelengths and oscillator strengths with a non-perturbative treatment of the magnetic field. While highly accurate calculations have previously been performed for hydrogen and helium, the variational techniques employed become computationally intractable for systems with more than three to four electrons. Modern computational techniques, such as finite-field coupled-cluster theory, allow the calculation of many-electron systems in arbitrarily strong magnetic fields. Because around 25 per cent of white dwarfs have metal lines in their spectra, and some of those are also magnetic, the possibility arises for some metals to be observed in very strong magnetic fields, resulting in unrecognizable spectra. We have identified SDSS J114333.48+661531.83 as a magnetic DZ white dwarf, with a spectrum exhibiting many unusually shaped lines at unknown wavelengths. Using atomic data calculated from computational finite-field coupled-cluster methods, we have identified some of these lines arising from Na, Mg, and Ca. Surprisingly, we find a relatively low field strength of 30 MG, where the large number of overlapping lines from different elements make the spectrum challenging to interpret at a much lower field strength than for DAs and DBs. Finally, we model the field structure of SDSS J1143+6615 finding the data are consistent with an offset dipole.

Comparing simulated and experimental spectral line splitting in visible spectroscopy diagnostics in the HL-2A tokamak

We established the passive-visible spectroscopy diagnostics (P-VSD) and active-VSD (A-VSD) spectral splitting models for the HL-2A tokamak. Spectral splitting due to the influence of electromagnetic fields on the spectra in VSD is studied. Zeeman splitting induced by the magnetic field ( B ) is used to distinguish reflected light overlap in the divertor for P-VSD. Stark splitting caused by the Lorentz electric field ( E Lorentz) from the neutral beam injection particle’s interaction with the magnetic field ( V beam× B ) is used to measure the safety factor q profile for A-VSD. We give a comparison and error analysis by fitting the experimental spectra with the simulation results. The distinguishing of edge (scrape-off layer and divertor) hydrogen/deuterium spectral lines and the q profile derived from the spectra provides a reference for HL-2M VSD.

Observation of Zeeman splitting effect in a laser-driven coil

The Zeeman splitting effect is observed in a strong magnetic field generated by a laser-driven coil. The expanding plasma from the coil wire surface is concentrated at the coil center and interacts with the simultaneously generated magnetic field. The Cu I spectral lines at wavelengths of 510.5541, 515.3235, and 521.8202 nm are detected and analyzed. The splittings of spectral lines are used to estimate the magnetic field strength at the coil center as ∼31.4 ± 15.7 T at a laser intensity of ∼5.6 × 1015 W/cm2, which agrees well with measurements using a B-dot probe. Some other plasma parameters of the central plasma disk are also studied. The temperature is evaluated from the Cu I spectral line intensity ratio, while the electron density is estimated from the Stark broadening effect.

HD 144941: the most extreme helium-strong star

Since its discovery about 50 yr ago, HD 144941 has generally been classified as a peculiar member of the extreme helium (EHe) supergiant stars, a very rare class of low-mass hydrogen-deficient stars. We report the detection of a strong longitudinal magnetic field based on spectropolarimetry with FORS2 on the ESO VLT with surface-averaged longitudinal field strengths as large as −9 kG. This is further constrained by the detection of Zeeman splitting of spectral lines to a field strength of at least 15 kG, explaining the recent finding of surface spots for this star. The quantitative analysis of the stellar atmosphere based on a hybrid non-local thermodynamic equilibrium approach and new optical spectra yields an effective temperature of 22 000 ± 500 K, a logarithmic surface gravity of 4.20 ± 0.10, and a surface helium fraction of 0.950 ± 0.002 by number. While the metal abundances are about a factor of 10 sub-solar in absolute number, the metal-to-hydrogen ratios are typical of massive early-type stars, indicating that helium fallback in a weak, fractionated stellar wind in the presence of a magnetic field took place – the canonical mechanism for the formation of the helium-strong phenomenon. Both the spectroscopic and the Gaia EDR3 parallax imply HD 144941 to be a luminous massive star. Kinematically, we argue that HD 144941 has reached its high Galactic latitude as a runaway star. We conclude that instead of being a comparatively high-gravity low-mass EHe star, HD 144941 is by far the most extreme member of the magnetic massive helium-strong stars, with almost all atmospheric hydrogen substituted by helium.

Detection of an extremely strong magnetic field in the double-degenerate binary merger product HD 144941

ABSTRACT HD 144941 is an extreme He (EHe) star, a rare class of subdwarf OB star formed from the merger of two white dwarf (WD) stars. Uniquely amongst EHe stars, its light curve has been reported to be modulated entirely by rotation, suggesting the presence of a magnetic field. Here, we report the first high-resolution spectropolarimetric observations of HD 144941, in which we detect an extremely strong magnetic field both in circular polarization (with a line-of-sight magnetic field averaged over the stellar disc 〈Bz〉 ∼−8 kG) and in Zeeman splitting of spectral lines (yielding a magnetic modulus of 〈B〉 ∼17 kG). We also report for the first time weak H α emission consistent with an origin and a centrifugal magnetosphere. HD 144941’s atmospheric parameters could be consistent with either a subdwarf or a main-sequence (MS) star, and its surface abundances are neither similar to other EHe stars nor to He-strong magnetic stars. However, its H α emission properties can only be reproduced if its mass is around 1 M⊙, indicating that it must be a post-MS object. Since there is no indication of binarity, it is unlikely to be a stripped star, and was therefore most likely produced in a WD merger. HD 144941 is therefore further evidence that mergers are a viable pathway for the generation of fossil magnetic fields.

Influence of local fields on the dynamics of four-wave mixing signals from 2D semiconductor systems

In recent years the physics of two-dimensional semiconductors was revived by the discovery of the class of transition metal dichalcogenides. In these systems excitons dominate the optical response in the visible range and open many perspectives for nonlinear spectroscopy. To describe the coherence and polarization dynamics of excitons after ultrafast excitation in these systems, we employ the Bloch equation model of a two-level system extended by a local field describing the exciton–exciton interaction. We calculate four-wave mixing (FWM) signals and analyze the dependence of the temporal and spectral signals as a function of the delay between the exciting pulses. Exact analytical results obtained for the case of ultrafast (δ-shaped) pulses are compared to numerical solutions obtained for finite pulse durations. If two pulses are used to generate the nonlinear signal, characteristic spectral line splittings are restricted to short delays. When considering a three-pulse excitation the line splittings, induced by the local field effect, persist for long delays. All of the found features are instructively explained within the Bloch vector picture and we show how the exciton occupation dynamics govern the different FWM signals.

Introduction of Zeeman splitting in CHIANTI

High-resolution spectra emitted by laboratory plasmas provide invaluable diagnostic tools for the measurement of plasma properties. To be implemented, they require a large amount of atomic data and transition rates, which are available in several spectral codes. In this paper we present a new feature added to the CHIANTI code, which allows us to calculate the Zeeman splitting of spectral lines in the presence of a magnetic field with known intensity and orientation. When combined with the CHIANTI database and software to calculate level populations and line emissivities, this new feature returns the emissivities in all four Stokes parameters, that can be utilized for the measurement of the magnetic field inside laboratory plasma chambers, along with other plasma parameters. This new feature can be applied to the analysis of the emission of laboratory plasmas created in different devices.

Optical isolation of spectral lines emitted by sputtered tungsten in a weakly magnetized plasma

Optical isolation of the clockwise or the counter-clockwise circular polarization of spectral lines was applied to emission of sputtered tungsten atoms. As a result one measures the weak magnetic field at plasma-surface interface resulting in splitting of spectral lines (W I at 4008.751 Å and 4982.593 Å) being negligibly small with respect to the Doppler broadening. One relies only on the phase rotation of a reflected circular polarized light propagating at the normal incidence to the mirror-like surface. The spectral shift of the signal from sputtered W atoms on the detector using high-resolution spectrometer provides the value of the magnetic field at a known dispersion, i.e. no further modeling or additional assumption on the distribution of atoms is required. The isolation of spectral line components is equivalent to isolation of the effect of the magnetic field from the measured line shape. It is complete for Zeeman triplet lines and partial for other lines. The results are found to be in a very good agreement of 3% with calculations and the Zeeman resolved laser absorption spectroscopy (10%) on metastable levels of Ar I atoms.

Ab-initio theory of photoionization via resonances.

We present an ab initio approach for computing the photoionization spectrum near autoionization resonances in multi-electron systems. While traditional (Hermitian) theories typically require computing the continuum states, which are difficult to obtain with high accuracy, our non-Hermitian approach requires only discrete bound and metastable states, which can be accurately computed with available quantum chemistry tools. We derive a simple formula for the absorption line shape near Fano resonances, which relates the asymmetry of the spectral peaks to the phase of the complex transition dipole moment. Additionally, we present a formula for the ionization spectrum of laser-driven targets and relate the "Autler-Townes" splitting of spectral lines to the existence of exceptional points in the Hamiltonian. We apply our formulas to compute the autoionization spectrum of helium, but our theory is also applicable for nontrivial multi-electron atoms and molecules.

The EPR spectra of a D4h symmetry four-nuclear molecular complex

A study of the EPR spectra of aspin s=1/2 four-nuclear single molecular magnet with D4h symmetry, having ferromagnetic nearest neighbor and local interactions such as the Dzyaloshinsky-Moriya (DMI), axial, and azimuthal anisotropy, was performed. The evolution of the spin tetramer EPR spectra is described as a function of the spin-spin interaction parameters. The impact of spin-mixing on the splitting of spectral lines is considered for intermultiplet and intramultiplet transitions. The study yields simple relations that connect the parameters of isotropic exchange interaction, DMI, and local anisotropy to the frequency ratios of certain spectral lines.