Spectroscopic Parameters Research Articles

Laser cooling with intermediate state of spin–orbit coupling of LuF molecule

This work presents a theoretical study of the laser cooling feasibility of the molecule LuF, in the fine structure level of approximation. An ab-initio complete active space self-consistent field (CASSCF)/MRCI with Davidson correction calculation has been done in the Λ(±) and Ω(±) representations. The corresponding adiabatic potential energy curves and spectroscopic parameters have been investigated for the low-lying electronic states. The calculated values of the internuclear distances of the X3Σ0+ and (1)3Π0+ states show the candidacy of the molecule LuF for direct laser cooling. Since the existence of the intermediate (1)3Δ1 state cannot be ignored, the investigation has been done by taking into consideration the two transitions (1)3Π0+−(1)3Δ1 and (1)3Π0+ −X3Σ0+. The calculation of the Franck–Condon factors, the radiative lifetimes, the total branching ratio, the slowing distance, and the laser cooling scheme study prove that the molecule LuF is a good candidate for Doppler laser cooling.

Observation of the electronic band system 23Σg--a3Πu of C2 in the vacuum ultraviolet region.

A systematic spectroscopic study of the dicarbon molecule C2 has important applications in various research fields, such as astrochemistry and combustion. In the short vacuum ultraviolet (VUV) wavelength region, recent theoretical calculations have predicted many absorption band systems of C2, but only few of them have been verified experimentally yet. In this work, we employed a tunable VUV laser radiation source based on the two-photon resonance-enhanced four-wave mixing method and a time-of-flight mass spectrometer to investigate the absorption bands of C2 in the VUV range of 64 000-66 000cm-1. The electronic transition 23Σg-(v')-a3Πu(v″) of C2 has been observed and identified experimentally for the first time. The term value Te for the 23Σg- state is determined to be 66 389.9 ± 0.5cm-1 above the ground state X1Σg+, and the vibrational and rotational constants are also determined. The experimentally measured spectroscopic parameters in this study are in excellent agreement with the theoretical results based on high-level abinitio calculations.

The ground, v2 = 1, 2 and v4 = 1 states of 14ND3 analyzed at experimental accuracy

Ammonia is the object of extensive investigations due to the peculiar pattern of its interacting vibration states and its central role in astronomical sciences. 14ND3 is of interest in astrochemistry because the determination of deuterium fractionation ratios in ammonia and its deuterated isotopologues contributes to a deeper knowledge of the chemistry in the cold, dense cores of the interstellar medium. Here, the ground, v2 = 1, 2 and v4 = 1, a, s states of 14ND3 are analyzed thanks to new spectra recorded with the Canadian Light Source synchrotron, from 60 to 1500 cm−1 at a resolution ranging from 0.00096 to 0.003 cm−1. Overall, 7765 inversion, rotation-inversion, and vibration–rotation-inversion transitions in ν2, 2ν2, ν4, 2ν2 ← ν2, 2ν2 ← ν4, ν4 ← ν2, ν2 ← ν2, 2ν2 ← 2ν2, and ν4 ← ν4 have been fitted simultaneously to characterize the s and a levels of the excited states. 4021 and 2388 transitions were assigned in the cold and hot bands, respectively, and 150 inversion and 1206 inversion-rotation transitions in v2 = 1, 2 and v4 = 1. The effective Hamiltonian adopted includes all symmetry allowed interactions between and within the studied excited states, according to the most recent results on ammonia. The transitions have been reproduced at experimental accuracy using 118 spectroscopic parameters, determined with high precision. In addition, a new analysis of the ground state has been performed. 9256 data have been fitted, 78 inversion and 837 rotation-inversion transitions, and 8341 ground state combination differences. An improved set of parameters and term values are derived thanks to the increased precision of the newly assigned rotation-inversion transitions with J/ K values up to 31/30 and to the larger number of the ground state combination differences.

Evaluation of carbonification of coals using a portable Raman spectrometer

AbstractThe estimation of the degree of carbonification of coals can be investigated using the Raman microspectroscopy applied for the analysis of grains of selected macerals (altered remains of organic particles). This approach allows for the best control of the analyses such as precise selection and orientation of the maceral grains to be analysed. On the other hand, the miniaturized, especially handheld Raman spectrometers typically offer a significantly less controlled environment with the issues including large laser spot sizes and the focusing issues. However, the advantages of the miniaturized spectrometers include fast analyses and the possibility of in situ analyses. This study illustrates that it is possible to discriminate among the coals of different degrees of maturation of the carbonaceous matter and other types of carbonaceous matter using the data acquired with a portable Raman spectrometer using spectroscopic parameters: D and G band widths and wavenumber positions. The issues inherent to the analyses of such heterogeneous materials such as coals using a portable spectrometer were addressed. Moreover, the variability in the Raman spectroscopic backgrounds of a wide range of coals from lignite to anthracite necessitated the utilization of a robust background removal function. This study shows that modern portable Raman spectrometers with the appropriate excitation are capable of basic discrimination among the different types of carbonaceous matter, with implications towards fast in situ analyses of carbonaceous matter in rocks as an additional tool for a geologist.

Accurate mass–radius ratios for Hyades white dwarfs

ABSTRACT We use the ESPRESSO spectrograph at the Very Large Telescope to measure velocity shifts and gravitational redshifts of eight bona fide Hyades white dwarfs, with an accuracy better than 1.5 per cent. By comparing the gravitational redshift measurements of the mass-to-radius ratio with the same ratios derived by fitting the Gaia photometry with theoretical models, we find an agreement to better than one per cent. It is possible to reproduce the observed white dwarf cooling sequence and the trend of the mass-to-radius ratios as a function of colour using isochrones with ages between 725 and 800 Myr, tuned for the Hyades. One star, EGGR 29, consistently stands out in all diagrams, indicating that it is possibly the remnant of a blue straggler. We also computed mass-to-radius ratios from published gravities and masses, determined from spectroscopy. The comparison between photometric and spectroscopic stellar parameters reveals that spectroscopic effective temperature and gravity are systematically larger than the photometric values. Spectroscopic mass-to-radius ratios disagree with those measured from gravitational redshift, indicating the presence of systematics affecting the white dwarf parameters derived from the spectroscopic analysis.

Assessment of UV-VIS spectra analysis methods for quantifying the absorption properties of chromophoric dissolved organic matter (CDOM)

Several ultraviolet-visible (UV-VIS) spectral analysis methods have been used to quantify the absorption properties of chromophoric or colored dissolved organic matter (CDOM). Different spectroscopic parameters can be used as surrogates of optical properties; furthermore, advanced mathematical tools have also been applied to investigate the absorption spectrum. This study evaluated the most commonly used spectroscopic parameters in remote sensing research and advanced mathematical methods using absorption data on primary biomass constituents (BCs) in aqueous states. We found that, out of the eight spectrometric parameters, the spectral slope in the 275–295 nm range (S275–295) had the strongest correlation with the hydrogen to carbon ratio (H/C), and the spectral slope ratio (275–295 to 350–400 nm) SR and the absorbance ratio between 465 and 665 nm (E4/E6) had a strong correlation with the oxygen to carbon ratio (O/C). Additionally, the spectroscopic parameter values for the solutions of the BCs exhibited distinguishable differences. Gaussian fitting was suitable for single CDOM components but not for complex mixtures. Derivative analysis can be used for single-component discrimination with an extensive investigation of the absorption properties of this component. Additionally, we propose a possible bottom-up perspective to track the origins of CDOM through the absorption spectrum.

Discriminating Congested Vibrational Peaks of Condensed Organic Materials with Time- and Frequency-Resolved Coherent Anti-Stokes Raman Scattering Spectroscopy

The spectral congestion of highly overlapping vibrational peaks of molecules in condensed phases is a persistent challenge in conventional linear vibrational spectroscopy, making it difficult to accurately determine the spectroscopic parameters. This study demonstrates the utility of time- and frequency-resolved coherent anti-Stokes Raman scattering (CARS) spectroscopy with a time-delayed picosecond probe pulse in resolving congested C-H stretching vibrational peaks of condensed organic matters. The results show that the overlapping vibrational peaks of polymeric films and oily liquids, which are not easily distinguishable in spontaneous Raman spectroscopy, can be separated in the time-resolved CARS (tr-CARS) spectra. To understand the physical basis of the enhanced spectral resolution, we examine the time series of CARS spectra obtained by varying the delay time between the pump and probe pulses. The global fit analysis indicates that the effective suppression of faster Raman free-induction-decay components and instantaneous nonresonant background signals contributes to improved spectral resolution. Additionally, the present study reveals that the CARS spectra at a sufficient probe delay time are highly sensitive to the incident and detection polarizations, further improving vibrational peak distinguishability through polarization-controlled tr-CARS.

Accurate Structures and Spectroscopic Parameters of Phenylalanine and Tyrosine in the Gas Phase: A Joint Venture of DFT and Composite Wave-Function Methods.

A general strategy for the accurate computation of conformational and spectroscopic properties of flexible molecules in the gas phase is applied to two representative proteinogenic amino acids with aromatic side chains, namely, phenylalanine and tyrosine. The main features of all the most stable conformers predicted by this computational strategy closely match those of the species detected in microwave and infrared experiments. Together with their intrinsic interest, the accuracy of the results obtained with reasonable computer times paves the route for accurate investigations of other flexible bricks of life.

The Solvation Effect of C=O Group of Cyclic Anhydrides in Solution.

The paper reports the results of investigation intermolecular interactions between alanine and sarcosine anhydride in organic solvents. The absorption frequencies of cyclic dipeptide in solvents were measured by IR spectroscopy. The effect of Van der Waals interactions and the hydrogen bonding of solvents on absorption frequencies of the C=O group of anhydrides was discussed. The spectroscopic parameters for C=O∙∙∙H-O hydrogen bonding complexes of anhydride with methanol in aprotic and proton donor solvent are obtained. In multi-particle complexes of dipeptides with aliphatic alcohols, the hydrogen bond enhancement was between 10 and 16%, which is significantly lower than it is for amide complexes.

Computational Protocol for the Identification of Candidates for Radioastronomical Detection and Its Application to the C3H3NO Family of Isomers

The C3H3NO family of isomers is relevant in astrochemistry, even though its members are still elusive in the interstellar medium. To identify the best candidate for astronomical detection within this family, we developed a new computational protocol based on the minimum-energy principle. This approach aims to identify the most stable isomer of the family and consists of three steps. The first step is an extensive investigation that characterizes the vast number of compounds having the C3H3NO chemical formula, employing density functional theory for this purpose. The second step is an energy refinement, which is used to select isomers and relies on coupled cluster theory. The last step is a structural improvement with a final energy refinement that provides improved energies and a large set of accurate spectroscopic parameters for all isomers lying within 30 kJ mol-1 above the most stable one. According to this protocol, vinylisocyanate is the most stable isomer, followed by oxazole, which is about 5 kJ mol-1 higher in energy. The other stable species are pyruvonitrile, cyanoacetaldehyde, and cyanovinylalcohol. For all of these species, new computed rotational and vibrational spectroscopic data are reported, which complement those already available in the literature or fill current gaps.

Influence of TiO2 concentration on near-infrared emission of germanate glasses doped with Tm3+ and Tm3+/Ho3+ ions

In this work, Tm3+ doped and Tm3+/Ho3+ co-doped germanate glasses with various TiO2 concentrations have been examined using optical spectroscopy. The broad emission bands corresponding to 3F4→3H6 (1.8 μm) and 5I7→5I8 (2 μm) transitions of thulium and holmium ions were registered, respectively. It was observed that the intensity of near-infrared emission bands significantly changes with increasing titanium oxide content in the glass composition. Furthermore, the energy transfer process from Tm3+ to Ho3+ ions in studied glass systems was confirmed and discussed. The dependence of spectroscopic parameters like full width at half maximum (FWHM) and energy transfer efficiency (ηET) on increased TiO2 concentration in glass host was established.

Deeper insights into the density functional theory of structural, optical, and photoelectrical properties using 5-[(4-oxo-4H-chromen-3-yl) methylidene]-4-oxo (thioxo)-6-thioxo-2-sulfido-1, 3, 2-diazaphosphinanes

The structure–activity relationship studied by DFT calculations and contacted with practical antimicrobial results for compounds 1–4 is discussed in detail. In light of this compounds 1–4 have been studied by using DFT/B3LYB/6-311++G (d,p) at the level of theory, the geometrical parameters, bond lengths and bond angles have been discussed. The results of quantum mechanical calculations showed that the presence of phosphorus and sulfur atoms changed the planarity of the parent compound 1 by the range from − 11 to 125°. The electronic parameter and dipole moment of these compounds in the ground state theoretically is analyzed by computing HOMO and LUMO pictures. Using frontier molecular orbital analysis, various spectroscopic and quantum chemical parameters are evaluated. Besides, absorption energies, oscillator strength, and electronic transitions of 1,3,2-diazaphosphinines 1–4 molecules have been derived at TD-DFT/CAM-B3LYP/6-311++G (d,p) computations utilizing, then the CAM-B3LYP method is “the Coulomb-attenuating method bases” set studied the electronic absorption spectra theoretically in the gas phase (TD-DFT) with the polarized split-valence 6-311++G (d, p) basis sets, in addition, the corrected linear response polarizable continuum model and measured experimentally in methanol and cyclohexane indicate a good agreement with the observed spectra (practically) in UV–Vis spectra. The molecular electrostatic potential surfaces plots have been computed to understand reactivity points.

Rotational spectroscopy of oxirane-2,2-[formula omitted], [formula omitted]-CD[formula omitted]CH[formula omitted]O, and its tentative detection toward IRAS 16293-2422 B

We prepared a sample of oxirane doubly deuterated at one C atom and studied its rotational spectrum in the laboratory for the first time between 120 GHz and 1094 GHz. Accurate spectroscopic parameters up to eighth order were determined, and the calculated rest frequencies were used to identify c-CD2CH2O tentatively in the interstellar medium in the Atacama Large Millimeter/submillimeter Array Protostellar Interferometric Line Survey (PILS) of the Class 0 protostellar system IRAS 16293-2422. The c-CD2CH2O to c-C2H4O ratio was estimated to be ∼0.054 with Trot=125 K. This value translates to a D-to-H ratio of ∼0.16 per H atom which is higher by a factor of 4.5 than the ∼0.036 per H atom obtained for c-C2H3DO. Such increase in the degree of deuteration referenced to one H atom in multiply deuterated isotopologs compared to their singly deuterated variants have been observed commonly in recent years.

Spectroscopic Parameters of 15 Low-Lying Doublet and Quartet Λ-S States as Well as 36 Ω States of VO

Spectroscopic Parameters of 15 Low-Lying Doublet and Quartet Λ-S States as Well as 36 Ω States of VO

Approximate mass spectra and root mean square radii of quarkonia using Cornell potential plus spin-spin interactions

We proposed a global spin-dependent potential energy function which fits the description of the non-relativistic quark model. The spin dependencies of our model result from the harmonic approximation of the Gaussian function in the spin-spin component. The approximation enables us to obtain analytical solutions of the bound states for the heavy mesons singlet and triplet states using the conventional Nikiforov-Uvarov method. The obtained mass spectra and expectation values for the low through high-lying quantum states are in agreement with the results obtained for other potential functions in the existing literature. The splitting of the masses occurs at a distance greater than the obtained characteristic radius of the heavy mesons which were found to be within the experimentally observed 1fm. The proposed potential model may be extended to obtain other meson spectroscopic parameters such as the decay constants, wave function at the origin and electromagnetic radiative transitions.

Improving the Path to Obtain Spectroscopic Parameters for the PI3K—(Platinum Complex) System: Theoretical Evidences for Using 195Pt NMR as a Probe

The absence of adequate force field (FF) parameters to describe certain metallic complexes makes new and deeper analyses impossible. In this context, after a group of researchers developed and validated an AMBER FF for a platinum complex (PC) conjugated with AHBT, new possibilities emerged. Thus, in this work, we propose an improved path to obtain NMR spectroscopic parameters, starting from a specific FF for PC, allowing to obtain more reliable information and a longer simulation time. Initially, a docking study was carried out between a PC and PI3K enzyme, aiming to find the most favorable orientation and, from this pose, to carry out a simulation of classical molecular dynamics (MD) with an explicit solvent and simulation time of 50 ns. To explore a new PC environment, a second MD simulation was performed only between the complex and water molecules, under the same conditions as the first MD. After the results of the two MDs, we proposed strategies to select the best amino acid residues (first MD) and water molecules (second MD) through the analyses of hydrogen bonds and minimum distance distribution functions (MDDFs), respectively. In addition, we also selected the best frames from the two MDs through the OWSCA algorithm. From these resources, it was possible to reduce the amount and computational cost of subsequent quantum calculations. Thus, we performed NMR calculations in two chemical environments, enzymatic and aqueous, with theory level GIAO–PBEPBE/NMR-DKH. So, from a strategic path, we were able to obtain more reliable chemical shifts and, therefore, propose safer spectroscopic probes, showing a large difference between the values of chemical shifts in the enzymatic and aqueous environments.

Study of Central Intensity Ratio of Seyfert Galaxies in Nearby Universe

We use the recently discovered simple photometric parameter Central Intensity Ratio (CIR) determined for a sample of 57 nearby (z < 0.02) Seyfert galaxies to explore the central features of galaxies and their possible connection with galaxy evolution. The sample of galaxies shows strong anti-correlation between CIR and mass of their central supermassive black holes (SMBHs). The SMBH masses of ellipticals are systematically higher for a given CIR value than those for lenticulars and spirals in the sample. However, the correlation between CIR and central velocity dispersion is weak. CIR appears less influenced by the excess flux produced by the central engine in these galaxies, when compared to spectroscopic parameters like velocity dispersion and O iv flux, and proves to be a fast and reliable tool for estimating central SMBH mass.

Cooperative hydrogen bonding in thiazole⋯(H2O)2 revealed by microwave spectroscopy.

Two isomers of a complex formed between thiazole and two water molecules, thi⋯(H2O)2, have been identified through Fourier transform microwave spectroscopy between 7.0 and 18.5GHz. The complex was generated by the co-expansion of a gas sample containing trace amounts of thiazole and water in an inert buffer gas. For each isomer, rotational constants, A0, B0, and C0; centrifugal distortion constants, DJ, DJK, d1, and d2; and nuclear quadrupole coupling constants, χaa(N) and [χbb(N) - χcc(N)], have been determined through fitting of a rotational Hamiltonian to the frequencies of observed transitions. The molecular geometry, energy, and components of the dipole moment of each isomer have been calculated using Density Functional Theory (DFT). The experimental results for four isotopologues of isomer I allow for accurate determinations of atomic coordinates of oxygen atoms by r0 and rs methods. Isomer II has been assigned as the carrier of an observed spectrum on the basis of very good agreement between DFT-calculated results and a set of spectroscopic parameters (including A0, B0, and C0 rotational constants) determined by fitting to measured transition frequencies. Non-covalent interaction and natural bond orbital analyses reveal that two strong hydrogen bonding interactions are present within each of the identified isomers of thi⋯(H2O)2. The first of these binds H2O to the nitrogen of thiazole (OH⋯N), and the second binds the two water molecules (OH⋯O). A third, weaker interaction binds the H2O sub-unit to the hydrogen atom that is attached to C2 (for isomer I) or C4 (for isomer II) of the thiazole ring (CH⋯O).

Vibrationally Resolved Inner-Shell Photoexcitation of the Molecular Anion C2.

Carbon 1s core-hole excitation of the molecular anion C2 - has been experimentally studied at high resolution by employing the photon-ion merged-beams technique at a synchrotron light source. The experimental cross section for photo-double-detachment shows a pronounced vibrational structure associated with and core excitations of the C2 - ground level and first excited level, respectively. A detailed Franck-Condon analysis reveals a strong contraction of the C2 - molecular anion by 0.2 Å upon this core photoexcitation. The associated change of the molecule's moment of inertia leads to a noticeable rotational broadening of the observed vibrational spectral features. This broadening is accounted for in the present analysis which provides the spectroscopic parameters of the C2 - and core-excited levels.

Machine learning-assisted cell-imprinted electrochemical impedance sensor for qualitative and quantitative analysis of three bacteria

In this work, a cell-imprinted electrochemical impedance sensor was developed for the qualitative and quantitative detection of three pathogenic bacteria through machine learning. A whole-cell imprinted polymer for three bacteria, Escherichia coli (EC), Staphylococcus aureus (SA) and Vibrio parahaemolyticus (VP), was prepared by electrochemical polymerization on the electrode surface using 3-aminophenylboronic acid as a monomer to build an electrochemical impedance sensor. Six electrochemical impedance spectroscopic (EIS) parameters were extracted to construct the dataset used as the feature input of the machine learning model. And, random forest algorithm was selected and optimized to construct a bacteria classifier, which could qualitatively identify and semi-quantitatively detect the three bacteria in a categorical form. In addition, quantitative detection in the concentration range of 1.0 × 101 ∼ 1.0 × 106 CFU/mL could be achieved by weighting classification concentrations through a normalization method, enabling sensitive, accurate, cheap and rapid detection of source dataset samples, non-source samples and real samples. This simple detection strategy can meet the requirement of rapid screening and diagnosis of pathogenic bacteria in the field.