Absorption Phenomena Research Articles

Rational Molecular Design for Balanced Locally Excited and Charge‐ Transfer Nature for Two‐Photon Absorption Phenomenon and Highly Efficient TADF‐Based OLEDs

The pursuit of highly efficient thermally activated delayed fluorescence (TADF) emitters with two‐photon absorption (2PA) character is hampered by the concurrent achievement of a small singlet‐triplet energy gap (ΔEST) and high photoluminescence quantum yield (ФPL). Here, by introducing a terephthalonitrile unit into a sterically crowded donor‐π‐donor structure, inducing a hybrid electronic excitation character, we designed unique TADF emitters possessing 2PA ability. This rational molecular design was achieved through a main π‐conjugated donor‐acceptor‐donor backbone in line with locally excited feature renders a large oscillator strength and transition dipole moment, maintaining a high 2PA cross‐section value. The ancillary N‐donor‐acceptor‐donor with charge transfer character highly balances the TADF phenomenon by minimizing ΔEST. A near‐unity ФPL value with a large radiative decay rate over an order of magnitude higher than the intersystem crossing rate and a high horizontal orientation ratio of 0.95 were simultaneously attained for TPCz2NP. The organic light‐emitting diodes fabricated with this material exhibit a high maximum external quantum efficiency of 25.4% with an elevated 2PA cross‐section (σ2) value up to 143 GM at 850 nm. These findings offer a venue for designing high‐performance TADF emitters with exceptional performance inclusive of 2PA properties, expanding for future functional material design.

Rational Molecular Design for Balanced Locally Excited and Charge- Transfer Nature for Two-Photon Absorption Phenomenon and Highly Efficient TADF-Based OLEDs.

The pursuit of highly efficient thermally activated delayed fluorescence (TADF) emitters with two-photon absorption (2PA) character is hampered by the concurrent achievement of a small singlet-triplet energy gap (ΔEST) and high photoluminescence quantum yield (ФPL). Here, by introducing a terephthalonitrile unit into a sterically crowded donor-π-donor structure, inducing a hybrid electronic excitation character, we designed unique TADF emitters possessing 2PA ability. This rational molecular design was achieved through a main π-conjugated donor-acceptor-donor backbone in line with locally excited feature renders a large oscillator strength and transition dipole moment, maintaining a high 2PA cross-section value. The ancillary N-donor-acceptor-donor with charge transfer character highly balances the TADF phenomenon by minimizing ΔEST. A near-unity ФPL value with a large radiative decay rate over an order of magnitude higher than the intersystem crossing rate and a high horizontal orientation ratio of 0.95 were simultaneously attained for TPCz2NP. The organic light-emitting diodes fabricated with this material exhibit a high maximum external quantum efficiency of 25.4% with an elevated 2PA cross-section (σ2) value up to 143GM at 850 nm. These findings offer a venue for designing high-performance TADF emitters with exceptional performance inclusive of 2PA properties, expanding for future functional material design.

Experimental characterization of thermal and viscous powers in porous media under oscillating flow

Porous materials are integrated components across various industries, offering unique properties such as high surface area, low density, and good permeability. They have a wide range of applications including energy conversion, with relevance in sound absorption and thermoacoustic phenomena. Understanding the intricate energy conversion mechanisms within the microstructure of porous materials under oscillating flows, such as sound waves, is paramount for optimizing their performance in these applications. The techniques currently used for testing porous materials enable the characterization of the behaviour of the porous matrix when subjected to an acoustic wave, without consideration to energetic quantities. Here, this paper presents two novel measurement techniques allowing for the experimental quantification of the power dissipated within the porous material, by making an explicit distinction between thermal relaxation and viscous dissipation effects. The study involves a model to quantify the viscous and thermal energetic behaviours from which analytical expressions guiding the elaboration of the proposed experimental techniques are derived, and finally validated through experimental data. Experimental tests have been carried out on three different samples (polyester fibers, wire mesh and triangular pores sample) largely used both in acoustic and thermoacoustic fields. The experimental data compared with the theoretical prediction for each sample allow to validate the measurement methodologies. By bridging theoretical modelling with experimental validation, this work contributes to the broader understanding and utilization of porous materials in energy conversion applications.

Investigating Quantum Confinement and Enhanced Luminescence in Nanoporous Silicon: A Photoelectrochemical Etching Approach Using Multispectral Laser Irradiation

This study explores electrochemical etching to form porous silicon (PS), which has diverse biomedical and energy applications. Our objective is to gain new insights and drive significant scientific and technological advancements. Specifically, we study the effect of electrochemical etching of P-type silicon using laser irradiation in a hydrofluoric acid (HF) solution. The formation of the nanoscale PS structure can be successfully controlled by incorporating laser irradiation into the electrochemical etching process. The wavelength and power of the laser influence the formation of nanoporous silicon (NPS) on the surface during the electrochemical etching process. The luminous flux is monitored with the help of a customized integrating sphere system and an LED-based excitation source to find the light flux values distributed across the P-type nanolayer PS wafers. Analysis of the NPS and luminescence characteristics shows that the laser bandwidth controls the band gap energy absorption (BEA) phenomenon during the electrothermal reaction. It is demonstrated that formation of the NPS layer can be controlled in this combined laser irradiation and electrochemical etching technique by adjusting the range of the laser wavelength. This also allows for further precise control of the numerical trend of the luminous flux.

Peierls Distortion Induced Giant Linear Dichroism, Second-Harmonic Generation, and In-Plane Ferroelectricity in NbOBr2.

The Peierls distortion plays an essential role in governing the in-plane ferroelectricity and nonlinear optical characteristics of anisotropic niobium oxide dihalides, such as NbOCl2 and NbOI2. Despite its significance, experimental investigation into the structural, optical, and ferroelectric properties of NbOBr2 has been lacking. Here, the successful fabrication of centimeter-sized, high-quality NbOBr2 single crystals, enabling direct observation of Peierls distortion using aberration-corrected scanning transmission electron microscopy, is reported. Notably, the magnitude of Peierls distortion in NbOBr2 falls between that observed in NbOCl2 and NbOI2. Furthermore, the existence of giant linear dichroism absorption and second-harmonic generation (SHG) phenomena associated with Peierls distortion is confirmed. Exfoliated NbOBr2 flakes exhibit single-domain ferroelectricity, with the polarization switchable by an electric field. Temperature-dependent SHG measurements reveal a Curie temperature of ≈502K for ferroelectric NbOBr2. This work demonstrates that NbOBr2 holds promise for polarized nonlinear optical devices, as well as for nonvolatile information processing and storage devices.

High Entropy Ceramics for Electromagnetic Functional Materials

AbstractMicrowave absorbing materials play an increasingly important role in modern electronic warfare technology for enhancing electromagnetic compatibility and suppressing electromagnetic interference. High‐entropy ceramics (HECs) possess extraordinary physical and chemical properties, and more importantly, the high tunability of multi‐component HECs has brought new opportunities to microwave absorbing materials. Rich crystallographic distortions and multi‐component occupancies enable HECs to have highly efficient microwave absorption properties, excellent mechanical properties, and thermal stability. Therefore, the structural advantages of HECs are integrated from comprehensive perspectives, emphasizing on the role of dielectric and magnetic properties in the absorption phenomenon. Strategies are proposed to improve the microwave absorption capacity of HECs, including composition optimization, microstructure engineering, and post‐treatment technology. Finally, the problems and obstacles associated with high‐entropy materials (HEMs) research are discussed. The innovative design concepts of high‐entropy microwave absorbing ceramics are highlighted.

Ultrafast carrier dynamics and transient nonlinear absorption in chalcogenide perovskite BaZrS3

The unique combination of excellent semiconducting properties in halide perovskites and the high stability and nontoxicity of oxide perovskites has led to a recent surge in interest in chalcogenide perovskite BaZrS3 for optoelectronic applications. However, to realize its potential in future device technologies, a comprehensive understanding of photoexcited carrier dynamics and transient optical response is imperative, yet it remains largely unexplored for BaZrS3. In this work, employing transient absorption spectroscopy, we have revealed that photoexcited carriers in epitaxial BaZrS3 nanofilms exhibit two exponential decay components relating to optical phonon cooling and interband recombinations. Meanwhile, our investigation unveils an intriguing transient nonlinear absorption phenomenon in BaZrS3, characterized by the ultrafast switching of the pump-induced transparency (i.e., the saturable absorption) to the absorption enhancement within a timescale commensurate with the measurement resolution (hundreds of femtosecond). This study provides crucial dynamic insights essential for leveraging chalcogenide perovskites, such as BaZrS3, in the development of advanced optoelectronic devices.

Underwater image restoration via spatially adaptive polarization imaging and color correction

Polarization imaging is extensively employed in underwater image restoration owing to its effectiveness in eliminating backscattered light. However, the existing polarization-based imaging methods rely on the strong assumption that the degrees of polarization (DoPs) of the target and backscattered light remain constant. Additionally, these methods ignore wavelength-specific absorption phenomena. To address these challenges, we propose an underwater image restoration method via spatially adaptive polarization imaging and color correction. First, based on optimal polarization difference images, we propose a method for calculating the spatial DoP of the target. In this method, the polarization characteristics of the target and background are fully exploited, and a scoring function is designed to achieve an optimal differential image. Second, we propose an adaptive local optimization method to estimate the spatial DoP of backscattering, which involves dividing the image into multiple local regions, and then employing improved particle swarm optimization (IPSO) algorithms to obtain the optimal value of DoP for each region. Finally, we introduce an adaptive compensation method based on the channel with minimal color absorption to correct color shifts during underwater polarization imaging. Extensive experiments demonstrate that our method exhibits superior generalization capability and outstanding restoration performance compared to existing methods.

3D-printed polarization-independent low-cost flexible frequency selective surface based dual-band microwave absorber

Abstract A 3D-printed polarization-independent low-cost lightweight and flexible frequency selective surface based dual-band microwave absorber is presented in this paper. Two concentric square loops fabricated at different heights using 3D printing technology are responsible for exhibiting dual-band responses at 3.32 GHz (S-band) and 5.46 GHz (C-band) with more than 97% absorptivities. The corresponding full widths at half maximum bandwidths are observed as 230 MHz (3.21–3.44 GHz) and 450 MHz (5.27–5.72 GHz). The proposed topology is polarization-insensitive owing to the four-fold symmetry. The absorption phenomenon is explained with the analysis of current distributions at the surface and impedance curves at the frequencies of resonance. Further, the performance has been evaluated for both planar and curved surfaces with different angles of curvature, and the good agreement between the measured and simulated responses confirms the flexible behavior of the proposed structure.

A Sustainable Solution for the Adsorption of C.I. Direct Black 80, an Azoic Textile Dye with Plant Stems: Zygophyllum gaetulum in an Aqueous Solution.

The presence of pollutants in water sources, particularly dyes coming by way of the textile industry, represents a major challenge with far-reaching environmental consequences, including increased scarcity. This phenomenon endangers the health of living organisms and the natural system. Numerous biosorbents have been utilized for the removal of dyes from the textile industry. The aim of this study was to optimize discarded Zygophyllum gaetulum stems as constituting an untreated natural biosorbent for the efficient removal of C.I. Direct Black 80, an azo textile dye, from an aqueous solution, thus offering an ecological and low-cost alternative while recovering the waste for reuse. The biosorbent was subjected to a series of characterization analyses: scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) method, X-ray diffraction (XRD), and infrared spectroscopy (IR) were employed to characterize the biosorbent. Additionally, the moisture and ash content of the plant stem were also examined. The absorption phenomenon was studied for several different parameters including the effect of the absorption time (0 to 360 min), the sorbent mass (3 to 40 g/L), the pH of the solution (3 to 11), the dye concentration (5 to 300 mg/L), and the pH of the zero-charge point (2-12). Thermodynamic studies and desorption studies were also carried out. The results showed that an increase in plant mass from 3 to 40 g/L resulted in a notable enhancement in dye adsorption rates, with an observed rise from 63.96% to 97.08%. The pH at the zero-charge point (pHpzc) was determined to be 7.12. The percentage of dye removal was found to be highest for pH values ≤ 7, with a subsequent decline in removal efficiency as the pH increased. Following an initial increase in the amount of adsorbed dye, equilibrium was reached within 2 h of contact. The kinetic parameters of adsorption were investigated using the pseudo-first-order, pseudo-second-order and Elovich models. The results indicated that the pseudo-first-order kinetic model was the most appropriate for the plant adsorbent. The isotherm parameters were determined using the Langmuir, Frendlich, Temkin, and Dubinin-Radushkevich models. The experimental data were more satisfactory and better fitted using the Langmuir model for the adsorption of dye on the plant. This study demonstrated that Zygophyllum gaetulum stems could be employed as an effective adsorbent for the removal of our organic dye from an aqueous solution.

From the few main colors to their spectra: discussion on robustness or mutability of a material’s color

The present work intends to bring a new approach to the creation of target colorations in pigment research and development. Rather than proposing a “chemist's” approach, i.e. based on knowledge of the accessible energy levels of the electrons in matter whose transfer will produce absorption phenomena, we propose here, “without any compositional guide”, to establish the spectra corresponding to the 6 main colors (red-green-blue-cyan-magenta-yellow): the created spectra for the modeling are created without trying to correspond to any specific composition. Hence, we propose herein a “process” which can be directly transferred to experimental spectra associated with experimental compounds, whatever their nature: organic or inorganic, metallic, semi-conducting or insulating, etc. Since “out of all compositional guide” does not mean “unrealistic”, we have first shown that inorganic pigments, which are made up of absorption phenomena associated with the three main types of electronic transfer, can be robustly simulated in absorbance space by a linear combination of Gaussian functions. Briefly, this work led us to show several interesting conclusions in successive stages: • A single phenomenon can already create yellow, magenta, and blue colors with very good agreement, • All colors can be created with two-Gaussian spectra, • Very different spectra can lead to the same coloration (metamerism, which is already largely documented in literature). We showed that these “metameric” spectra then have properties of robustness (maintenance of coloration) for a change of the illuminant or a shift in the energy position of the absorption bands, which can be highly variable. Some colorations are intrinsically more robust than others to these environmental changes.

A Carbazole-based Fluorescent Probe with AIE Performance and a Large Stokes Shift for Peroxynitrite Detection and Imaging in Live Cells.

A carbazole-based fluorescent probe YCN with AIE performance and a large Stokes shift (242nm) shift was synthesized by attaching 4-acetonitrile pyridine to the 3-phenylaldehyde butylcarbazole. Its structure was characterized by 1H NMR, 13C NMR and MS. Probe YCN has high selectivity and sensitivity toward ONOO-. The addition of ONOO- to the probe YCN solution results in a noticeable color change from pale yellow to colorless under natural light, and a fluorescent color change from bright orange-yellow to bright yellow-green under a 365nm UV lamp, which can be distinguished by the naked eye. The research results on the reaction mechanism showed that when YCN reacted with ONOO-, -C = C- was oxidized and broken into -CHO, and the ICT effect was significantly inhibited, resulting in changes in UV absorption and fluorescence emission phenomenon. The recognition mechanism was verified by 1H NMR, mass spectrometry (MS) and density function theory (DFT) calculations. The experiments of live cells imaging suggested that compound YCN can be used as a fluorescent probe for the detection of ONOO- in HeLa cells. This result indicates that YCN has potential application prospects in the biological aspects.

Effect of the coconut fibers and cement on the physico-mechanical and thermal properties of adobe blocks

This work aimed to investigate the effect of cement and coconut fibers on the thermal and physico-mechanical characteristics of adobe blocks. Thus, a clayey raw material consisting of kaolinite (62 wt%), quartz (31 wt%), goethite (2 wt%) with a plasticity index of 21.5 % was used to manufacture adobe blocks amended with cement and coconut fibers. First the adobe blocks were formulated with an optimal cement content of 4 wt% before adding coconut fibers up to 1 wt%. The physico-mechanical and thermal characteristics of manufactured composites were then studied. According to the results obtained, the incorporation of coconut fibers into the clay-cement matrix decreases the apparent density and volume shrinkage and increases the porosity of the adobe blocks. The presence of coconut fibers in adobe blocks promotes the phenomenon of water absorption. The combined effect of the formation of calcium silicate hydrate (CSH) and hydrogen bonds between fibers molecules and those of clayey minerals leads to an improvement in the mechanical properties of adobe blocks. The thermal conductivity of adobe blocks decreases with the fiber content due to the presence of pores and cellulose molecules in the fibers which have an insulating nature. Taking into account their physico-mechanical and thermal properties, adobe blocks containing 0.6 wt% coconut fibers and 4 wt% cement are suitable for building sustainable habitats and thermally comfortable.

Poly(acrylic acid)-Sodium Alginate Superabsorbent Hydrogels Synthesized by Electron-Beam Irradiation-Part II: Swelling Kinetics and Absorption Behavior in Various Swelling Media.

Hybrid hydrogels with superabsorbent properties based on acrylic acid (20%), sodium alginate (0.5%) and poly(ethylene oxide) (0.1%) were obtained by electron-beam irradiation between 5 and 20 kGy, and are characterized by different physical and chemical methods; the first results reported showed gel fractions over 87%, cross-link densities under 9.9 × 103 mol/cm3 and swelling degrees of 400 g/g. Two types of hydrogels (without and with 0.1% initiator potassium persulfate) have been subjected to swelling and deswelling experiments in different swelling media with different pHs, chosen in accordance with the purpose for which these superabsorbent materials were obtained, i.e., water and nutrients carriers for agricultural purposes: 6.05 (distilled water), 7.66 (tap water), 5.40 (synthetic nutrient solution) and 7.45 (organic nutrient solution). Swelling kinetics and swelling dynamics have been also studied in order to investigate the influence of swelling media type and pH on the absorption phenomenon. The swelling and deswelling behaviors were influenced by the hydrogel characteristics and pH of the swelling media. Both the polymeric chain relaxation (non-Fickian diffusion) and macromolecular relaxation (super case II) phenomenon were highlighted as a function of swelling media type.

Magnetic field enhanced laser absorption on a metallic surface incorporated with shape-dependent nanostructures

Abstract This communication proposes an analytical model to investigate the nanoparticle-based nonlinear absorption phenomenon associated with an obliquely incident p-polarized laser beam on a metallic surface. In this scheme, the surface is ingrained with noble-metal spherical nanoparticles and cylindrical nanoparticles in the presence of an external static magnetic field. The absorption of laser energy in the presence of nanoparticles (NPs) is attributed to surface plasmon resonance and enhanced magnetic-field effects. The absorption phenomenon is significantly enhanced by the incorporation of nanostructures and a magnetic field. The ellipticity characterizing parameter, which significantly influences the resonant frequency of different nanometric structures, has also been analysed and discussed. The effects of varying the magnetic field intensity, incident angle, size, and spacing of the NP were examined to determine their influence on the anomalous absorption of the laser. Furthermore, a direct dependency was found between the absorption coefficient and transmission coefficient of the incident laser, as well as the dimensions of the NPs. Several applications have direct relevance to this study, including biosensors such as DNA sensors and immunosensors, photothermal therapy, photoacoustic imaging, optoelectronic devices, solar cells, and surface-enhanced Raman spectroscopy.

Photoelectrocatalytic property and DFT calculations of TiO2 with broadened infrared light absorption by Gd2O3:Er3+

In this paper, erbium-doped gadolinium oxide rare earth oxide nanoparticles (Gd2O3:Er3+) with good light absorption capacity from the visible to the infrared region were prepared by polyol method, and then compounded with TiO2 by hydrothermal method. SEM, TEM, XPS, UV–vis and electrochemical workstation were used to study the morphology, structure, UV–vis light absorption and photoelectrochemical (PEC) properties of Gd2O3:Er3+/TiO2. The results showed that the Gd2O3:Er3+ spherical nanoparticles with a particle size of about 15 nm were uniformly distributed on the surface of the TiO2 nanorod array, and the Gd2O3:Er3+/TiO2 nanocomposites had good light absorption capacity in the infrared region. Furthermore, the photocurrent densities of Gd2O3/TiO2 and Gd2O3:Er3+/TiO2 were 2.08 and 2.75 times higher than those of TiO2, respectively, manifesting that the broadening of infrared light absorption can improve the PEC property of TiO2. Meanwhile, the DFT calculation results showed that the energy band of Gd2O3:Er3+/TiO2 was significantly narrower than that of TiO2, indicating that Gd2O3:Er3+/TiO2 had a redshift phenomenon of UV–vis absorption. The calculation results of state density showed that the f orbital of Gd2O3:Er3+ intersected with the d orbital of TiO2, indicating that there is an electron transfer between Gd2O3:Er3+ and TiO2.

Ligand-controlled UV light absorption property and neuromorphic behavior of a new Th(IV)- bisphosphoramide complex

This article describes the synthesis and photophysical properties of a new furan-based bisphosphoramide ligand (L) and its Th(IV) complex characterized by various analytical and spectroscopic techniques. As expected, L, associated with several double bonds within the structure and the possible π → π* transitions, displays strong absorption in the UV region. Notably, the absorption of UV light decreases significantly in an exclusive manner for the L-Th4+ complex, and such behavior was not observed with most of the transition metals as well as f-metal ions. The ligand-to-metal binding ratio of L-Th4+ was found to be 1:1 through the Job’s plot. This photophysical property was successfully explored in the selective determination of Th4+ ions in aqueous solutions. The limit of detection (LOD) for Th4+ and limit of quantitation (LOQ) were determined to be 1.04 x 10-7 M and 3.472 x 10-7 M, respectively. In order to get an insight at the molecular level, a density functional theory (DFT) investigation was performed to comprehend the sensing mechanism and interaction in the detection of Th4+ by L. Furthermore, this salient UV light absorption phenomenon was employed in exploring the artificial synaptic behavior of the L-Th4+ complex which can have remarkable memory and applications in neuromorphic devices.

Cathodoluminescence emission and electron energy loss absorption from a 2D transition metal dichalcogenide in van der Waals heterostructures

Nanoscale variations of optical properties in transition metal dichalcogenide (TMD) monolayers can be explored with cathodoluminescence (CL) and electron energy loss spectroscopy (EELS) using electron microscopes. To increase the CL emission intensity from TMD monolayers, the MoSe2 flakes are encapsulated in hexagonal boron nitride (hBN), creating van der Waals (VdW) heterostructures. Until now, the studies have been exclusively focused on scanning transmission electron microscopy (STEM-CL) or scanning electron microscopy (SEM-CL), separately. Here, we present results, using both techniques on the same sample, thereby exploring a large acceleration voltage range. We correlate the CL measurements with STEM-EELS measurements acquired with different energy dispersions, to access both the low-loss region at ultra-high spectral resolution, and the core-loss region. This provides information about the weight of the various absorption phenomena including the direct TMD absorption, the hBN interband transitions, the hBN bulk plasmon, and the core losses of the atoms present in the heterostructure. The S(T)EM-CL measurements from the TMD monolayer only show emission from the A exciton. Combining the STEM-EELS and S(T)EM-CL measurements, we can reconstruct different decay pathways leading to the A exciton CL emission. The comparison with SEM-CL shows that this is also a good technique for TMD heterostructure characterization, where the reduced demands on sample preparation are appealing. To demonstrate the capabilities of SEM-CL imaging, we also measured on a SiO2/Si substrate, quintessential in the sample preparation of two-dimensional materials, which is electron-opaque and can only be measured in SEM-CL. The CL-emitting defects of SiO2 make this substrate challenging to use, but we demonstrate that this background can be suppressed by using lower electron energy.

Sunflower Pollen-Derived Microspheres Selectively Absorb DNA for microRNA Detection.

Herein, we report the finding that a naturally sunflower pollen-derived microspheres (HSECs) with hierarchical structures can selectively absorb polyC and polyA with high efficiency and affinity. HSECs exhibit the capability to selectively absorb polyC and polyA ssDNA under neutral and acidic conditions. It has been observed that the presence of metal cations, specifically Ca2+, enhances the absorption efficiency of HSECs. Mechanically, this absorption phenomenon can be attributed to both electrostatic interactions and cation-π interactions. Such an appealing property enables the functionalization of HSECs for broad potential biomedical applications, such as microRNA detection.

Simulation of Gas Sweetening Process using Extended NRTL and Stages Efficiency as Modeling Approach

Gas sweetening is a process to remove CO2 and H2S from natural gas. The current established technology is by using Amine contactor where the solvent used is in form of Amine solution. To simulate the effect of different solvent, electrolyte-NRTL is used to model the equilibrium, and mass transfer-kinetic is used to model the rate-based processes. This modeling approach is rather complex and available only in commercial and proprietary process simulation software. Therefore we propose an alternative modeling approach where we use extended NRTL and stage efficiency to model the acid gas absorption processes. We find that this approach is quite good to describe CO2 absorption, yet unsuccessful to calculate the H2S absorption. Inadequate vapor liquid equilibrium parameter regression for H2S, specifically at low partial pressure might cause the problem. However the stage efficiency approach shows good result where it is comparable to rate-based model and corresponds to current understanding of physico-chemical phenomenon of acid gas absorption.