Ultraviolet Absorption Spectroscopy Research Articles

Study on Nitrite Nitrogen Based on Ultraviolet Visible Absorption Spectrometry

In order to improve the accuracy of nitrite nitrogen detection, this template proposed a method for rapid determination of nitrite nitrogen in water based on ultraviolet visible absorption spectroscopy. The experimental object is the absorption spectrum of sodium nitrite standard solution with a concentration range of 0.1 to 17 mg·L-1, the continuous projection algorithm SPA (Continuous Projections Algorithm) is used to screen out the characteristic wavelengths related to nitrite nitrogen. the absorbance at the characteristic wavelengths and the sample concentration are fitted using Support Vector Regression (SVR) to establish a regression model for nitrite nitrogen, The decision coefficient R2 and root mean square error RMSE are used as the evaluation indicators of the model. The experiment found that the R2 and RMSE of the mixed prediction model established using the continuous projection algorithm support vector regression (SPA-SVR) modeling method were 0.999654 and 0.000479 mg·L-1 respectively, and their modeling effects were better than those of the three mixed prediction models, KPCA-SVR, PCA-SVR, and Lasso-SVR, achieving rapid and accurate measurement of nitrite nitrogen.

Hydrogen sulfide measurement of combustion gaseous product using ultraviolet absorption spectroscopy

Measurement of hydrogen sulfide (H2S) in gaseous product can provide direct reference for high-temperature corrosion of industrial combustion equipment. Aiming at the interference effect of overlapping measurement of absorption spectrum for H2S and other combustion gas components in UV absorption spectroscopy, the simulation calculation of ultraviolet band absorption spectrum of the typical gaseous products of coal combustion were carried out. The cross interference effects of combustion gaseous products were analyzed in detail. Due to the SO2 and H2S gas under typical combustion condition have equivalent absorption strength in the 228 nm-233 nm band, the influence of SO2 on H2S concentration inversion must be emphatically considered, and the inversion algorithm of H2S gas concentration under the background interference of combustion gaseous products SO2 was put forward. In order to validate the measurement accuracy by the inversion algorithm, the measurement experiments of gas mixture of H2S and SO2 were carried out. The results show that the algorithm can effectively solve the problem of cross interference between the detection of H2S and SO2 in the combustion gaseous products by UV absorption spectroscopy. On this basis, the sampling, pre-treatment and H2S gas concentration measurement system for boiler flue gas near the wall was developed and applied to measure H2S concentration of flue gas near the wall in a 1000 MW ultra-supercritical coal-fired power generation boiler. The results can provide important references for combustion adjustment and high-temperature corrosion prevention of boiler.

Effects of ultrasound on the structural and functional properties of sheep bone collagen

The study evaluated the effect of an ultrasound-assisted treatment on the structural and functional properties of sheep bone collagen (SBC). The type and distribution of SBC were analyzed by proteome (shotgun) technology combined with liquid chromatography-tandem mass spectrometry. Compared with pepsin extraction, the ultrasound-assisted treatment significantly increased the collagen extraction rate by 17.4 pp (P < 0.05). The characteristic functional groups and structural integrity of collagen extracted by both methods were determined via Fourier transform infrared spectroscopy, ultraviolet absorption spectroscopy, and fluorescence spectroscopy. Circular dichroism spectra revealed that the ultrasound-assisted pretreatment reduced α-helix content by 1.6 pp, β-sheet content by 21.9 pp, and random coils content by 28.4 pp, whereas it increased β-turn content by 51.9 pp (P < 0.05), compared with pepsin extraction. Moreover, ultrasound-assisted treatment collagen had superior functional properties (e.g., solubility, water absorption, and oil absorption capacity) and foaming and emulsion properties, compared with pepsin extraction. Furthermore, the relative content of type I collagen in ultrasound-assisted extracted SBC was highest at 79.66%; only small proportions of type II, VI, X, and XI collagen were present. Peptide activity analysis showed that SBC had potential antioxidant activity, dipeptidyl peptidase 4 inhibitory activity, and angiotensin-converting enzyme inhibitory activity; it also had anticancer, antihypertensive, anti-inflammatory, and immunomodulatory effects.

Nitrate Measurement in Seawater with a Turbidity Correction Algorithm based on Ultraviolet Spectrophotometry

Turbidity usually has a great impact on the actual measurement of the value of nitrate concentrations in the seawater. In this study, a new turbidity correction approach for nitrate concentrations measurement in the seawater based on ultraviolet absorption spectroscopy is presented. Experiments were carried out to prove the improvement of the turbidity correction method with ultraviolet spectroscopy. The orthogonal projections to latent structures (O-PLS) algorithm was chosen to correct the additional information in absorbance caused by turbidity. The experimental results show that the influence of turbidity could be excellently removed. Compared with the standard normalized variate (SNV) transformation, the O-PLS algorithm could better reduce the influence of turbidity on the nitrate absorbance and improve the measurement accuracy in turbid seawater. The linear correlation coefficient (R2) of the prediction results in test samples is 0.9999 and RMSEP is 0.1886 μmol/L.

Carrier and Phonon Dynamics in Multilayer WSe2 Captured by Extreme Ultraviolet Transient Absorption Spectroscopy

Carrier and phonon dynamics in a multilayer WSe2 film are captured by extreme ultraviolet (XUV) transient absorption (TA) spectroscopy at the W N6,7, W O2,3, and Se M4,5 edges (30–60 eV). After the broadband optical pump pulse, the XUV probe directly reports on occupations of optically excited holes and phonon-induced band renormalizations. When compared with density functional theory calculations, XUV transient absorption due to holes is identified below the W O3 edge whereas signals at the Se M4,5 edges are dominated by phonon dynamics. Therein, 0.4 ps hole relaxation time, 1.5 ps carrier recombination time, and 1.7 ps phonon heating time are extracted. The acquisition of hole and phonon-induced signals in a single experiment can facilitate the investigation of the correlations between electron and phonon dynamics. Furthermore, the simultaneous observation of signals from different elements can be further extended to explore photochemical processes in multilayers and alloys, thereby providing key information for their applications in electronics, photocatalysts, and spintronics.

Green synthesis of iron nanoparticles using Cleistocalyx operculatus leaves extract and application iron nanoparticles to treat oganic dye Methylene Blue

Green synthesis is a potential method and increasingly popular for synthesizing nanoparticles. In this study, iron nanomaterial was green sythesized using Cleistocalyx operculatus leaves extract as reducing agent. Morphology and structure of the as-prepared nanomaterial was characterized by scanning microscope, X-ray diffraction analysis methods. The collected product is iron nano material with the morphology is paticles with the diameter is approximatly 100 nm. The iron nanomaterial revealed the high degradation performance toward Methylene Blue (MB) solution. The removal color of MB is determined and confirmed by the visible ultraviolet (UV-Vis) absorption spectroscopy which is proportional to the amount of nanomaterial used and is influenced by pH conditions.

Up-conversion and downconversion studies of Nd3+ doped borophosphate glasses

Neodymium doped borophosphate glasses have been synthesizsed by melt quenching technique to investigate their luminescence properties. The increase in density and decrease in molar volume with increasing concentration of Nd2O3 (0.1 mol% to 0.5 mol%) established the participation of Nd3+ in the glass structure. Non-crystalline nature of prepared glasses is confirmed by the absence of sharp peaks in X-ray diffraction spectra. The various structural units due to B2O3, P2O5, and PbO were identified by Fourier transform infrared spectroscopy. Ultraviolet visible absorption spectroscopy showed various absorption peaks/bands at 742 nm (4F7/2+4S3/2), 684 nm (4F9/2), 626 nm (2H11/2), 581 nm (4G5/2+2G7/2), 523 nm (4G7/2+4G9/2+ 2K13/2), 431 nm (2D5/2+2P1/2), 358 nm (4D3/2+4D5/2), 338 nm (2I11/2), and 315 (4D7/2+2I13/2+2L15/2). The optical parameters, namely indirect band gap, molar refractivity, molar polarizability, electronic polarizability and dielectric constant showed linear trend with increasing concentration of Nd2O3. Judd-Ofelt parameters followed Ω6> Ω4> Ω2 trend. The experimental and calculated oscillator strength for 584 nm is highest among all transitions because it is hypersensitive in nature. Upon 806 nm excitation, four visible peaks at 489 nm, 540 nm, 605 nm and 671 nm were observed. Excited state absorption up-conversion and energy transfer up-conversion mechanisms were responsible for visible up-conversion. At 338 nm, ultraviolet energy is downconverted to 448 nm, 529 nm, 591 nm. Commission International de I'Eclairage (CIE) chromaticity coordinates were evaluated from the up-conversion emission spectra and the coordinates lie in green region.

Effect of SWEEPS and PIPS techniques on dye extrusion in photodynamic therapy procedure after root canal preparation

AimThe aim of this study is to measure and compare the amount of apical extrusion of the methylene blue as photosensitizer using Laser-activated irrigation(LAI) techniques (SWEEPS, PIPS) and photodynamic therapy (PDT). Materials and methods40 single-rooted premolar teeth were selected and their root canals were cleaned and prepared. The photosensitizer, Methylene blue (MB), was used as dye which applied inside the root canals and the access cavities. Then the teeth were randomly allocated to 4 groups. Different techniques (SWEEPS, PIPS, PDT) were used in 3 groups. One group received no activation. Data related to the concentration of the extruded methylene blue was measured using ultraviolet and visible (UV–Vis) absorption spectroscopy. Absorption peak intensity of MB in the wavelength of 668 nm was considered as the concentration index according to Beer Lambert law. Taking into account the normal distribution of this data, one-way ANOVA analysis was used to evaluate the effects of the independent variables on the amount of apical extrusion of the irrigant. ResultsBased on the results of ANOVA analysis, there was no significant difference between the amounts of apical extrusion of MB between different groups (p = 0.628) ConclusionUsing SWEEPS and PIPS techniques, despite diffusion of the photosensitizer, didn't lead to any difference in the amount of apical extrusion. Therefore, these LAI techniques can be used safely for root canal irrigation.

Design of Carbon Nanocomposites Based on Sodium Alginate/Chitosan Reinforced with Graphene Oxide and Carbon Nanotubes.

The aim of this study was to use a simple, low-cost and environmentally friendly synthesis method to design nanocomposites. For this purpose, carbon nanostructures were used to reinforce the chitosan/alginate bond in order to improve the mechanical, solubility, water absorption and barrier (protection against UV radiation) properties of the chitosan/alginate structure. Scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), ultraviolet and visible light absorption spectroscopy (UV-VIS) and color analysis were utilized, and the thickness and mechanical properties of the obtained films were determined. The tests that were carried out showed an equal distribution of nanostructures in the composite material and the absence of chemical interactions between nanoparticles and polymers. It was also proven that the enrichment of the polysaccharide composite with graphene oxide and carbon nanotubes positively affected its absorption, mechanical capabilities and color.

Temperature and anion ligand field dependence of LnCl3 (Ln = Nd, Dy, Sm) electronic absorption spectra in LiCl–KCl eutectic molten salt

A comprehensive knowledge of the coordination, bonding, and speciation of elements in molten salt mixtures is necessary to understand and predict the chemical and physical properties of the salt. Absorption spectroscopy can yield information about the chemistry of species of interest in alkali halide molten salt mixtures by revealing information about the electronic structure and transitions of those species. In this study, ultraviolet (UV), visible (vis), and near-infrared (NIR) absorption spectroscopy was used to examine changes to the electronic structure of trivalent Nd, Sm, and Dy in LiCl–KCl eutectic molten salt with changes in temperature and the anion composition of the melt. With increasing temperature, changes to spectral features suggest a distortion of the coordination complexes. Changes to lineshape with the substitution of alternative halide anions were examined and analyzed, revealing differences in the coordination for I− versus F− with the lanthanides. Gaussian peak fitting was used to show that the changes in lineshape with the progressive addition of F− anions can be explained by the superposition of a set of absorption bands from complexes with all Cl− anion ligands and a set of blueshifted absorption bands from complexes containing both F− and Cl− anion ligands. This work yields a new method to analyze and interpret change to electronic absorption spectra for f-block elements dissolved in alkali halide molten salts as well as new observations of the interactions of larger and smaller halide anions with lanthanides in Cl−-based molten salts.

Ozone Concentration Measurement of an Atmospheric Pressure Air Plasma Jet by Ultraviolet Absorption Spectroscopy

Atmospheric pressure plasma jets have great potentials for various biomedical applications due to abundance with active oxygen species. In this article, an air plasma jet with a geometry of microhollow cathode discharge has been developed, which operates in a pulsed mode or a continuous mode depending on the dissipated power of the plasma jet. There are some continuous spectra emitted from the plasma jet, whose integrated intensity indicates that electron density increases with the increase of dissipated power, while decreases with increasing air flow rate for both of the two modes. Moreover, the electron density in the continuous mode is higher than that in the pulsed mode. Gas temperature of the plasma jet is obtained by the best fitting of the simulated and the experimental optical emission spectrum of OH (A-X), and ozone concentration produced by the plasma jet is measured by means of ultraviolet absorption spectroscopy. Results indicate that both ozone concentration and gas temperature decrease with increasing distance from the jet nozzle. At the jet nozzle, both of them increase with increasing dissipated power. However, ozone concentration decreases, while gas temperature increases with increasing air flow rate. The results are very important for the biomedical application of plasma jet.

Effect of freezing-air thawing pretreatment of cutting fluid wastewater on the organics' distribution, transfer and transformation

The cutting fluid wastewater was treated by freezing-air thawing method. After thawing, stable stratification occurred in the thawing wastewater, and the froth floated on the liquid surface, and the liquid from top to bottom was divided into the first layer, the second layer, the third layer and the fourth layer. The molecular weight (MW) distribution and organics characteristics of the froth layer and each layer wastewater were analyzed by ultrafiltration membrane filtration combined with mass balance, three-dimensional fluorescence excitation-emission matrix spectroscopy, ultraviolet absorption spectroscopy, flourier transform infrared spectroscopy and droplet size analysis. The results showed that the cutting fluid wastewater contained 66.74 % organics with MW > 100 kDa and 17.04 % organics with MW < 1 kDa, and the organics might contain aromatic and heterocyclic compounds. After three times of freezing-air thawing: 27.53 % of organic matter was volatilized into the air; the froth layer was mainly macromolecular organic matter with MW > 100 kDa, accounting for 94.59 %; from the froth layer to the fourth layer wastewater, the content of macromolecules with MW > 100 kDa gradually decreased, while the content of small molecules with MW < 1 kDa gradually increased. The results of molecular weight distribution analysis, spectroscopy analysis and droplet size analysis indicated that during the freezing-air thawing process, there was not only the demulsification maybe but also the destruction of molecular structure. The molecular weight distribution of the mixture of the froth layer and the fourth layer wastewater were close to that of the raw cutting fluid wastewater, so the mixture of the froth layer and the fourth layer wastewater could be reused in metal process. The wastewater in the first, second and third layers had better biodegradability, which could be treated by biological method.

Analysis of ozone generation in a planar atmospheric pressure air dielectric barrier discharge reactor

This work investigates O3 production in a planar atmospheric pressure air dielectric barrier discharge reactor numerically and experimentally. The surface temperature of the reactor is measured by an infrared (IR) thermal imager, and the O3 densities of cases in the reactive zone are measured by ultraviolet absorption spectroscopy. The 1.5D plasma fluid model (PFM) with transverse convection is employed to capture the average properties of a single microdischarge (MD) generated in the reactor. The concept of equivalent reaction is proposed to calculate spatial-cyclic average species sources obtained by the 1.5D PFM and provided to the chemical model of a 3D gas flow model (GFM) for obtaining density distributions of reactive species generated by MDs in the reactive zone. The simulated temperature distribution of the reactor surface is validated by that measured with the IR thermal imager since the gas temperature was reported as a critical discharge parameter for O3 generation. The simulated O3 densities show the same trend as the flow rate changes, which demonstrates the proposed model captures the average discharge dynamics in different operating conditions. In the 1.5D PFM, the simulated results show that the O3 molecules produced in the case of 4 SLM are much more than those produced in the case of 1 SLM though the O atoms produced in the case of 1 SLM are around 20% more than those produced in the case of 4 SLM. In the case of 1 SLM, more than 48% of O3 molecular generated are destructed, while only around 14% of O3 molecules are destructed in the case of 4 SLM. The analysis shows that around 73% of O atoms generated in the 1.5D PFM are consumed in the formation of O3 molecules in the case of 4 SLM, while only 18% of O atoms generated in the case of 1 SLM are consumed in the formation of O3 molecules. In the 3D GFM, the O3 destructed is around 24% of that destructed in the 1.5D PFM in the case of 4 SLM due to the oxidation reaction of NO, while only 11% of O3 molecules destructed as that destructed in the 1.5D PFM in the case of 1 SLM. The amounts of O3 molecules generated in the 3D GFM are minor if they are compared with those generated in the 1.5D PFM in all cases. The overall O3 yield efficiency reaches 97 g kWh−1 with the O3 concentration increasing up to 2700 ppm in the case of 4 SLM, while the O3 yield efficiency decreases to 10 g kWh−1 and O3 concentration drops to 1400 ppm in the case of 1 SLM.

Synthesis and characterization studies of glycine 4-nitrophenolate crystal doped with nickel chloride

Crystals with nonlinear optical characteristics have wide applicability in laser optics and communication. Glycine − 4- Nitrophenolate crystals doped with Nickel chloride were synthesized from the aqueous solution by using a slow evaporation technique at constant temperature. The various characterisation studies were carried out for the crystal synthesised using the proposed approach. The crystallinity nature of doped synthesised crystals were determined using XRD Pattern. The existence of different functional groups for this synthesised crystal was observed with the help of Fourier Transform Infrared Spectroscopy (FTIR) which is in the range of 600–4000 cm−1. The synthesized crystal also exhibits good optical transmittance which was examined using ultraviolet and visible (UV–vis) absorption spectroscopy. The band gap energy was calculated to be 3.37 eV. The thermal stability characteristics of the complex Glycine − 4- Nitrophenolate crystals doped with Nickel chloride crystals were studied using thermogravimetric analysis (TG) and differential thermal analysis (DTA) and it was noticed that it is stable up to 230 °C. The SEM studies were also carried out to study the morphology of this synthesised crystals. Thus, synthesized crystals exhibits favourable features for nonlinear optical applications observed from the characterization studies.

Improve color stability of plant extract dye through chemical grafting of laccase to wood substrate

Plant-derived extract can be a potential eco-friendly dye used to color the wood, especially for wood from fast-growing tree that usually is neutral in color. In this study, the extract from heat-treated larch (Larix gmelinii (Rupr.) Kuzen.) was used to dye poplar wood (Populus tomentosa Carr.). The laccase-catalyzed grafting was used to improve the color stability. The color stability was evaluated with the CIELab system, color fastness, and color strength (K/S), and the mechanism of dyeing and anti-UV was characterized with Gas chromatography mass spectrometry (GC-MS), ultraviolet absorption spectroscopy (UV), and Fourier transform infrared spectroscopy (FTIR). The results indicated that the color stability to water, UV, and open environment can be improved significantly through the grafting of extract to wood substrate. The color fastness to water boiling, UV irradiation, or outdoor exposure of extract-dyed poplar wood was higher than that of AGR-dyed poplar, and can be further improved by enzymatic grafting. The total color difference ΔE * of extract-grafted poplar after water boiling, UV irradiation, or outdoor exposure was 5.9, 9.0, or 7.7, which was significantly lower than that of extract-dyed poplar (ΔE * =7.9, 9.5, or 11.0) or AGR-dyed poplar (ΔE * =14.3, 13.0, or 13.4). The extract-grafted poplar wood had exhibited satisfied color stability at various environmental conditions. Larch extract dye grafted poplar has color tending to be dark with hues of red and yellow. The compounds in extract dye consist of isovanillic acid, methyl vanillate, a nd the UV absorber BP-6 that have contributed to the dyeing effect. This method can be used to realize residues reuse of wood industry by-products and the production of dyed wood with satisfactory color stability.

Indazole-derived synthetic cannabinoids: Absolute configuration determination and structure characterization by circular dichroism and DFT calculations

An increasing number of products containing synthetic cannabinoids pose a growing crisis to public health worldwide. Recently, a rising number of cases of serious adverse health effects, intoxications, and death cases associated with synthetic cannabinoids were reported. The current study represents the comprehensive structural analysis of three new synthetic cannabinoids (AB-, ADB- and AMB-FUBINACA) in solution investigated by electronic and vibrational circular dichroism together with the conventional methods of infrared and ultraviolet absorption spectroscopy, all supported by the density functional theory (DFT) calculations. The best level of theory to reproduce the experimental wavenumbers and wavelengths was found to be the B3PW91 method with a 6-311++G(d,p) basis set including the implicit solvent effect simulation. Very good agreement between the experimental and simulated spectra allowed us to determine the absolute configuration and a detailed interpretation of the IR absorption, VCD, ECD and UV spectra of AB-, ADB- and AMB-FUBINACA. In addition, the HOMO and LUMO electronic transitions were calculated.

Enantioseparation and a comprehensive spectroscopic analysis of novel synthetic cathinones laterally substituted with a trifluoromethyl group

Recently, the number of structural modifications of synthetic cathinones has been growing making them the second largest group of new psychoactive substances in Europe. Although they are abused because of their various psychoactive effects, some compounds from this group also serve as pharmaceuticals. Since synthetic cathinones are chiral molecules with one chiral center, their biological, toxicological, and pharmacological properties may significantly differ according to their absolute configuration and enantiomeric excess. In this study, we have synthesized two substances bearing a pharmacologically interesting trifluoromethyl group and developed a chiral liquid chromatography method using a polysaccharide chiral stationary phase to separate the corresponding enantiomers of both these drugs. Subsequently, we utilized molecular spectroscopic methods including chiroptical (electronic circular dichroism and vibrational circular dichroism) and non-polarizable (infrared and ultraviolet absorption) spectroscopies. In combination with density functional theory calculations, we have obtained stable conformers of selected enantiomers in solution and their relative abundances, which we used to simulate their spectra. The experimental and calculated data have been used to elucidate the 3D structure of the enantiomerically pure compounds and assign the absolute configuration of all prepared compounds.

Evidence of excited-state lifetime enhancement in dimyristoyl-phosphocholine nanodiscs by ultraviolet absorption spectroscopy

Ultraviolet absorption spectroscopy is an analytical tool that is commonly utilized to determine protein concentrations, primarily due to characteristic absorption of tryptophan and tyrosine at 280 nm. Accurate concentration determination is essential to the accuracy of many biophysical techniques, and ultraviolet absorption provides a convenient and rapid method to assess protein concentration. However, the widespread usage of this method assumes that ultraviolet absorption is the same for individual amino acids in aqueous solution (where the molar extinction coefficient was measured) as for the amino acid in the conformational environment of the protein of interest. We demonstrate that additional considerations may be necessary for the membrane scaffold protein in dimyristoyl-phosphocholine nanodiscs through ultraviolet absorption spectroscopy of nanodiscs, liposomes, the membrane scaffold protein, and a mixture of liposomes and the non-nanodisc-associated protein. The aromatic amino acids of the membrane scaffold protein absorb significantly less light at 280 nm when associated with lipids in a lipoprotein assembly, which we plausibly attribute to an enhancement of chromophore excited-state lifetimes due to reduced intramolecular motion in the nanodisc. We caution that using the molar absorptivity of the membrane scaffold protein alone to determine nanodisc concentrations may not yield accurate results. Instead, the molar absorptivity of each nanodisc formulation should be explored independently to account for the unique conformational environment of each nanodisc.

Study on the concentration retrieval of SO2 and NO2 in mixed gases based on the improved DOAS method.

NO2 and SO2 are important components of air pollutants, and their absorption spectra are superimposed at 193-253 nm. The superposed spectra affect the gas concentration retrieval based on the ultraviolet differential optical absorption spectroscopy (DOAS) method. In this study, a suitable wavelength band was chosen for concentration retrieval, moreover, the characteristics of the quasi-periodic variation of absorption cross-section with wavelength was given sufficient attention and then the superposed spectra were separated by the Fast Fourier transform (FFT) method. The concentration of the gases to be measured was calculated according to the relationship between the amplitude of absorbance after FFT and the gas concentration. The experimental results prove that by using an absorption cell with a 700 mm optical path, the relative deviation absolute value of the retrieval concentration of SO2 in a NO2 and SO2 gas mixture is less than 1.471%, and that of NO2 in a NO2 and SO2 gas mixture is less than 7.207%. The method has good adaptability, high detection precision, whether single SO2, NO2 or a mixture of both, and important reference value for the development of DOAS and future research on the high-precision detection of more types of mixed gases in the ultraviolet band, such as gas mixtures of NO2, SO2 and NO in flue gas.

Observation of Refractive Index Line Shape in Ultrafast XUV Transient Absorption Spectroscopy

Ultrafast extreme ultraviolet (XUV) transient absorption spectroscopy measures the time- and frequency-dependent light losses after light–matter interactions. In the linear region, the matter response to an XUV light field is usually determined by the complex refractive index n ˜ . The absorption signal is directly related to the imaginary part of n ˜ , namely, the absorption index. The real part of n ˜ refers to the real refractive index, which describes the chromatic dispersion of an optical material. However, the real refractive index information is usually not available in conventional absorption experiments. Here, we investigate the refractive index line shape in ultrafast XUV transient absorption spectroscopy by using a scheme that the XUV pulse traverses the target gas jet off-center. The jet has a density gradient in the direction perpendicular to the gas injection direction, which induces deflection on the XUV radiation. Our experimental and theoretical results show that the shape of the frequency-dependent XUV deflection spectra reproduces the refractive index line profile. A typical dispersive refractive index line shape is measured for a single-peak absorption; an additional shoulder structure appears for a doublet absorption. Moreover, the refractive index line shape is controlled by introducing a later-arrived near-infrared pulse to modify the phase of the XUV free induction decay, resulting in different XUV deflection spectra. The results promote our understanding of matter-induced absorption and deflection in ultrafast XUV spectroscopy.