Pressure-induced Shifts Research Articles

Towards improved spectroscopic applications in multi-gas environments: CO2 spectral line parameter measurement and analysis

The ν1 + 2ν2 + ν3 band of 12CO2 is dominated by weak absorption lines near 2.0 uμm, which has potential application in planetary atmosphere, astrophysical, and hydrocarbon fuel combustion investigations. High-quality spectral line parameters are the foundation of spectroscopic technology. In this work, high-resolution infrared spectra of CO2 were recorded over 5005–5008 cm−1 range using a Distributed Feedback (DFB) laser with a linewidth of Δν < 0.0001 cm−1. H2-, N2-, O2-, Ar-, air- and CO2- line-intensity, collision broadening coefficients, pressure shift coefficients were determined for CO2 transitions R44e, R46 e, R48 e, R50 e at room temperature. Voigt and Rautian profiles were utilized to retrieve the measured line shape of each individual transition at various pressures. The new data extend and complement previous measurements over the target spectral region. In addition, a comprehensive analysis of the measured spectral line shape parameters is conducted to elucidate the characteristics of spectral line intensity, broadening, and pressure-induced shift coefficients under different molecular collision conditions. This has the potential to be valuable for modeling spectral calculations of multi-component systems, optimizing multi-gas environmental spectral calculation, and developing new spectral diagnostic methods.

Heterogeneity dynamics: influencing rock type responses to overburden pressure, Permian–Triassic of the Persian Gulf

This study considers the impact of reservoir pressures on rock type variations within the Permian–Triassic formations in the Persian Gulf. Lithological composition, textures, visible porosity, pore types, and cementations of 328.85 m of carbonate rocks from Kangan and Dalan formations were determined using a polarizing microscope. Porosity, permeability, and rock types were analyzed under ambient and reservoir pressures. Findings showed limestone’s frequent rock type changes under reservoir pressure via the Winland method, while dolomite samples showed significant alterations using the flow zone indicator method. Grainstones predominated overall, persisting even amidst pressure-induced rock type shifts, indicating texture’s minimal influence. Pore throat size of low porosity samples rapidly decreased under reservoir pressure, leading to substantial rock type changes. Fewer alterations were observed based on permeability-to-porosity ratio via the flow zone indicator method. Additionally, low permeability samples exhibited varied rock types under the Winland method, while flow zone indicator method transitions mainly occurred within specific permeability ranges. In essence, this study offers a detailed understanding of pressure’s intricate interplay with rock types and properties in Persian Gulf carbonate reservoirs.

Pressure-induced band gap shift and enhanced optical properties of quaternary Heusler TaAlCuCo: DFT study

Pressure-induced band gap shift and enhanced optical properties of quaternary Heusler TaAlCuCo: DFT study

Revisiting Jupiter's deuterium fraction in the rotational ground-state line of HD at high spectral resolution

The cosmic deuterium fraction, set by primordial nucleosynthesis and diminished by subsequent astration, is a valuable diagnostic tool to link the protosolar nebula to the history of star formation. However, in the present-day Solar System, the deuterium fraction in various carriers varies by more than an order of magnitude and reflects environmental conditions rather than the protosolar value. The latter is believed to be preserved in the atmospheres of the gas giant planets, yet determinations inferred from the CH$_3$D/CH$_4$ pair require a larger fractionation correction than those from HD/H$_2$, which are close to unity. The question of whether a stratospheric emission feature contaminates the absorption profile forming in subjacent layers was never addressed, owing to the lack of spectral resolving power. Here we report on the determination of the Jovian deuterium fraction using the rotational ground-state line of HD ($J=1-0$) at $ Employing the GREAT heterodyne spectrometer on board SOFIA, we detected the HD absorption and, thanks to the high resolving power, a weak stratospheric emission feature underneath; the former is blue-shifted with respect to the latter. The displacement is attributed to a pressure-induced line shift and reproduced by dedicated radiative-transfer modeling based on recent line-profile parameters. Using atmospheric standard models, we obtained $ D/H $, which agrees with a recent measurement in Saturn's atmosphere and with the value inferred from solar-wind measurements and meteoritic data. The result suggests that all three measurements represent bona fide protosolar D/H fractions. As a supplement and test for the consistency of the layering assumed in our model, we provide an analysis of the purely rotational $J=6-5$ line of CH$_4$ (in the vibrational ground state, at $ mu$m).

Accurate reference spectra of HD in an H2–He bath for planetary applications

Context. The hydrogen deuteride (HD) molecule is an important deuterium tracer in astrophysical studies. The atmospheres of gas giants are dominated by molecular hydrogen, and the simultaneous observation of H2 and HD lines provides reliable information on the D/H ratios on these planets. The reference spectroscopic parameters play a crucial role in such studies. Under the thermodynamic conditions encountered in these atmospheres, spectroscopic studies of HD require not only the knowledge of line intensities and positions but also accurate reference data on pressure-induced line shapes and shifts. Aims. Our aim is to provide accurate collision-induced line-shape parameters for HD lines that cover any thermodynamic conditions relevant to the atmospheres of giant planets, namely any relevant temperature, pressure, and perturbing gas composition (the H2–He mixture). Methods. We performed quantum-scattering calculations on our new, highly accurate ab initio potential energy surface (PES), and we used scattering S matrices obtained in this way to determine the collision-induced line-shape parameters. We used cavity ring-down spectroscopy to validate our theoretical methodology. Results. We report accurate collision-induced line-shape parameters for the pure rotational R(0), R(1), and R(2) lines, the most relevant HD lines for investigations of the atmospheres of the giant planets. Besides the basic Voigt-profile collisional parameters (i.e., the broadening and shift parameters), we also report their speed dependences and the complex Dicke parameter, which can influence the effective width and height of the HD lines up to almost a factor of 2 for giant planet conditions. The sub-percent-level accuracy reached in this work is a considerable improvement over previously available data. All the reported parameters (and their temperature dependences) are consistent with the HITRAN database format, hence allowing for the use of the HITRAN Application Programming Interface (HAPI) for generating the beyond-Voigt spectra of HD.

Coefficients of Carbon Dioxide Pressure-Induced Line Shift of Sulfur Dioxide at Room Temperature: The ν1 + ν3 Band

Coefficients of Carbon Dioxide Pressure-Induced Line Shift of Sulfur Dioxide at Room Temperature: The ν1 + ν3 Band

The effect of pressure on degradation kinetics of polyphenols: Impact of polyphenol structure at hyperbaric storage conditions

Understanding reaction kinetics at elevated pressures is essential for developing efficient pressure-based technologies. It is especially vital for hyperbaric storage (HS), where pressure is applied for long durations. In single and multi-component models, the influence of pressure on the degradation kinetics of different catechins and anthocyanins was studied at accelerated conditions using neutral pH at pressures up to 200 MPa (HS levels) for several hours. In the neutral baroresistant buffer, pressure enhanced the degradation of all tested flavonoids with a negative activation volume. Despite the significant structural variety and major differences in the degradation rates within each tested subgroup, no significant structure-dependent effect of pressure on the activation volume was observed, which is suggestive of a similar mechanism by which pressure accelerates the degradation. The antioxidant capacity of catechins was not affected by pressure compared to control samples when the concentration of the original catechin was similar. Industrial relevanceA better understanding of pressure effects on the degradation reaction kinetics of food components can contribute to the general understanding of mechanisms related to food component degradation under high-pressure treatments. Plant-based foods are rich in polyphenolic compounds and responsible for sensory characteristics and their related health-promoting properties. In conditions similar to HS, that are known to inhibit and even, in some cases, inactivate microorganisms, when food is exposed to high pressures for a long time, it is imperative to investigate the effect of pressure on polyphenol degradation kinetics, which can lead to differences in the polyphenol compositions during the pressurized storage. However, the impact of pressure on polyphenol degradation kinetics is often overlooked. This study provides fundamental information regarding the polyphenol structure-dependent degradation kinetics of catechins and anthocyanins under pressure while taking into account the often overlooked pressure-induced pH shifts. The presented work can promote the development of novel storage and processing technologies based on high pressure that will better preserve oxidation-liable compounds with lower energetic costs.

Fluorescence and absorption of rhodamine 6G solutions as pressure standards for a diamond-anvil cell.

The absorption and fluorescence spectra of rhodamine 6G (R6G) dissolved in water, methanol, ethanol and isopropanol have been applied to calibrate the pressure in a diamond anvil cell (DAC). Owing to the strong initially nearly linear temperature-independent bathochromic shift of 7 nm GPa-1 found in absorption and emission bands for methanol R6G solutions, they are ideal for precise pressure calibration to over 3.4 GPa, when methanol freezes. Analogous bathochromic shifts as a function of pressure are revealed for aqueous, ethanolic and isopropanolic solutions. The pressure-induced shifts are considerably reduced in the crystallized solution. Practical protocols are presented to calibrate high pressures with R6G solutions.

The Molecular Ocean

We report on progress in observing the hydrogen-bonded structure of water and sea water by deep-ocean Raman spectroscopy. In the normal ocean, the abundance of single H2O species is less than 20%. The principal form is the tetrahedral pentamer, and the (H2O)[Formula: see text] nH2O equilibrium plays a dominant role in controlling physicochemical processes and the speed of sound. The enthalpy of the H-bond in water is 2.624 kcal/mol, and in sea water 2.258 kcal/mol due to the quantity of non-HB water in the solvation shell of sea salt ions. The activation energy of viscous flow is 4.28 kcal/mol at one atmosphere pressure, consistent with the need to break hydrogen bonds and overcome the van der Waals intermolecular forces. The activation energy decreases exponentially with depth/pressure and is 10% less at 4,000 m depth. We suggest this is due to the pressure-induced shift in the water equilibrium to favor the less compressible quasi-planar pentamer, tetramer, and so on forms. We address the long-standing conclusion that microbial swimming by means of rotating flagella is only 1%–2% efficient. This neglects the need for microbes to overcome the activation energy of viscous flow; [Formula: see text]95% of the mechanical energy produced by the flagella must be used to break H-bonds and overcome intermolecular forces.

A correlation between hydroxyl vibrations under compression and anharmonicity: glaucophane as a test case

The infrared hydroxyl bands and first hydroxyl combination bands of glaucophane are characterized under pressure. In this weakly hydrogen-bonded mineral, the anharmonicity parameter, as determined from the difference between combinations and the fundamentals, is nearly constant with pressure to 15 GPa, indicating that the ambient pressure value of hydroxyl-bond anharmonicity closely reflects its value at high pressures. Given this near-constancy, the Grüneisen parameters of the hydroxyl stretching vibrations of a wide range of minerals, as derived from the pressure dependence of their O–H stretching frequencies, are correlated with the anharmonic parameter of each vibration, as determined from the ambient pressure offset of the summed frequencies of the fundamental n = 0 to 1 transitions and the frequency of the hydroxyl combination or overtone band corresponding to the n = 0 to 2 transition. This correlation is motivated by (1) the anharmonic origin of the Grüneisen parameter; and (2) the grossly similar form of the interatomic potential governing weak- and medium-strength hydrogen bonding in many minerals. This possible correlation provides a means through which the likely pressure-induced hydroxyl mode shifts of phases might be estimated from ambient pressure near-infrared measurements and emphasizes the importance of near-infrared combination/overtone band measurements. In this context, the combination/overtone bands of high-pressure hydrous phases are almost completely uncharacterized, and thus one probe of their anharmonicity has been neglected. Such information directly constrains the nature of hydrogen bonding in these phases, and hence provides possible insights into both their retention of hydrogen and its mobility. Deviations from the anharmonicity-Grüneisen parameter correlation, when observed (as may be the case in prehnite), could provide insights into anomalous effects on the hydroxyl potential well induced by bifurcated H-bonds, pressure-dependent Davydov splitting, or the influence of neighboring cations.

High-pressure response of vibrational properties of b-As x P1–x : in situ Raman studies

The structural evolution of black arsenic-phosphorous (b-As x P1–x ) alloys with varying arsenic concentrations was investigated under hydrostatic pressure using in situ Raman spectroscopy. High-pressure experiments were conducted using a diamond anvil cell, which revealed pressure-induced shifts in vibrational modes associated with P–P bonds (A 1 g , A 2 g , ), As–As bonds (A 1 g , A 2 g , ), and As–P bonds in b-As x P1–x alloys. Two distinct pressure regimes were observed. In the first regime (region I), all vibrational modes exhibited a monotonic upshift, indicating phonon hardening due to hydrostatic pressure. In the second regime (region II), As0.4P0.6 and As0.6P0.4 alloys displayed a linear blueshift (or negligible change in some modes) at a reduced rate, suggesting local structural reorganization with less compression on the bonds. Notably, the alloy with the highest As concentration, As0.8P0.2, exhibited anomalous behavior in the second pressure regime, with a downward shift observed in all As–As and As–P Raman modes (and some P–P modes). Interestingly, the emergence of new peaks corresponding to the Eg mode and A 1g mode of the gray-As phase was observed in this pressure range, indicating compressive strain-induced structural changes. The anomalous change in region II confirms the formation of a new local structure, characterized by elongation of the P–P, As–As, and As–P bonds along the zigzag direction within the b-As x P1–x phase, possibly near the grain boundary. Additionally, a gray-As phase undergoes compressive structural changes. This study underscores the significance of pressure in inducing structural transformations and exploring novel phases in two-dimensional materials, including b-As x P1–x alloys.

Control of fully heat-integrated pressure-swing distillation with strict pressure manipulation: A case study of separating a maximum-boiling azeotrope with small pressure-induced shift

Pressure-swing distillation (PSD) is an alternative configuration used to separate pressure-sensitive azeotropes and avoid product contamination(s) in extractive or heterogeneous azeotropic distillation via the entrainer(s). Full heat integration between high- and low-pressure columns (HPC and LPC) can provide significant energy savings compared to the conventional case, while it also loses the control degree of freedom, trim condenser or reboiler heat load, via the integrated condenser/reboiler exchanger. Typically, the pressure of HPC is left uncontrolled, and additional pressure-compensated control strategies are implemented, which may create safety issues. To address this, the study proposes adding an auxiliary cooling-water-driven condenser to the fully heat-integrated PSD system, providing an extra manipulated variable to regulate the pressure of HPC. Compared to the conventional PSD system, the new modified process could achieve a 26.31% reduction in total annual cost. The research uses the maximum-boiling azeotropic mixture of acetone/chloroform as a case study which makes the distillation system characterized by high reflux ratios and a large recycle flow rate, leading to the unwelcome snowball effect. To achieve effective process control, robust control structures are proposed that rigorously regulate the pressure of the column by manipulating the heat removal in the trim condenser, attenuating or eliminating potential overpressure issues. Product purity and other evaluation indicators, such as product transient deviations, offsets, integral absolute error, and oscillation degrees, are also considered. Results show that the proposed control schemes can efficiently control the pressure of HPC, weaken the snowball effect, and maintain product purity. This study highlights the importance of pressure control for fully heat-integrated PSD systems, particularly for pressure-sensitive azeotropes with small pressure-induced shifts.

Multimodal, super-sensitive luminescent manometer based on giant pressure-induced spectral shift of Cr3+ in the NIR range

The remote pressure readout is of vital application importance as it will facilitate and in many cases enable rapid diagnostics. For most of the luminescent manometers described to date, the sensitivity of the pressure readout is limited by the relatively small pressure-induced spectral shift of the emission band. In response to this limitation, in this work, we present a super-sensitive and temperature-invariant NIR emitting luminescent manometer based on LiScGeO4:Cr3+. The 4T2→4A2 emission band of Cr3+ ions undergoes in this manometer a linear spectral shift with a rate of dλ/dp = 23.63 nm/GPa, which is the highest value reported in the literature to date. In addition, by using a ratiometric approach, this manometer has a relative sensitivity exceeding 120%/GPa. Importantly, the developed optical manometer operates in the NIR spectral region, providing good light permeability in the non-transparent systems, having high absorption in the visible range. Moreover, in the case of high-pressure luminescence experiments, the use of the developed sensor will eliminate spectral overlapping issues, as the vast majority of the organic and inorganic phosphors emitting in the visible range.

Dynamics and control of electrified pressure-swing distillation for separating a maximum-boiling azeotrope featuring small pressure-induced shift

Pressure-swing distillation (PSD) is a typical thermal-driven technique for separating pressure-sensitive azeotropes. By implementing heat pump assisted distillation (HPAD) and self-heat recuperation technology (SHRT), the process can be modified as an electrical-driven one. Previous works have verified the overwhelming steady-state economic advantages of electrified PSDs over a conventional design. However, highly integrated electrified processes could jeopardize the dynamics and controllability. In light of potential dynamic control issues, a demonstrating case of a maximum-boiling acetone/chloroform azeotrope featuring a small pressure-induced shift was studied. Severe snowball effects were observed in these complicated electrified systems. To maintain process stability under throughput and composition disturbances, several robust control structures based on decentralized proportional-integral feedback controllers were developed. These control structures feature temperature controllers with no composition measurement. The results indicate that there is no conflict between the steady-state advantage and dynamic controllability. Therefore, considering the great advantages in economic and environmental aspects of electrified PSD, it is encouraged to extend process electrification measures to other distillation processes.

The rotational spectrum of HD broadened by H2 at temperatures between 100 – 296 K

Laboratory measurements of the R(0) – R(3) pure rotational transitions of hydrogen deuteride (HD) have been performed at low pressures (< 1 bar) and temperatures between 98 and 296 K. The measurements were conducted using a Fourier transform spectrometer coupled to the Soleil synchrotron far-infrared source to obtain pure HD and HD-H2 mixture spectra. The observed spectra have been fitted using a non-linear least-squares multispectral fitting program. For each transition the line position, intensity, pressure broadening, pressure-induced frequency shift, and the temperature dependencies of these quantities have been determined simultaneously. These spectroscopic line parameters are compared to previous measurements made at higher gas pressures. Notably the present, and previous, measurements of the self- and H2-broadened linewidths are smaller by a factor of five compared with those listed in the HITRAN and GEISA databases. This work is applicable to the low pressure, low temperature regimes found in the atmospheres of the giant gaseous planets.

Temperature-shift-suppression scheme for two-photon two-color rubidium vapor clocks

We propose a scheme for interrogating a warm rubidium vapor using two different clock lasers. Performance wise, this approach is distinctly different from the recently proposed two-color two-photon rubidium clocks as our scheme does not trade off the ac Stark suppression against an increased sensitivity to the cell temperature or pressure. Instead, our approach compensates both the ac Stark shift and the temperature and pressure-induced frequency shifts. The proposed scheme also makes use of the modulation transfer technique, which enables a two orders of magnitude increase in the signal-to-noise ratio compared to traditional clocks that rely on fluorescence measurements.

Temperature invariant ratiometric luminescence manometer based on Cr3+ ions emission

The dependence of the spectroscopic properties of the phosphor on the applied pressure enables the development of luminescent manomenters that allow remote readout and imaging of the pressure. Although the most widely used manometers for years have been those using pressure-induced spectral shift of the emission band, their main limitations are relatively low sensitivity for spectrally narrow emission lines or low readout precision for broadband phosphors. Taking advantage of the benefits of both these approaches, this paper proposes a ratiometric pressure-readout strategy that exploits spectral shift of the 4T2→4A2 emission band of Cr3+ ions in Li2Mg3TiO6. The luminescent manometer developed in this way is characterized by a linear dependence of LIR on pressure in the range of 0–7.75 GPa pressure range and a relative sensitivity of SR = 4.7 %/GPa. Importantly, this manometer is characterized by insensitivity to temperature changes in the 123–563 K. This novel approach will allow the development of a new group of highly sensitive luminescent manometers.

H2, He, and CO2 Pressure-induced Parameters for the HITRAN Database. II. Line Lists of CO2, N2O, CO, SO2, OH, OCS, H2CO, HCN, PH3, H2S, and GeH4

In recent years, extended efforts have been made to increase the potential for modeling and interpreting the spectra of planetary atmospheres using the HITRAN database. A significant objective is to provide broadening parameters due to the ambient pressure of He, H2, and CO2 gases. Since hydrogen and helium are the main constituents in the atmospheres of gas giants, and carbon dioxide dominates the atmospheres of many rocky planets, these spectroscopic data are essential for radiative transfer models dedicated to planetary atmospheres. In HITRAN2016, the He-, H2- and CO2-broadening parameters and their temperature dependencies, and in some cases pressure-induced shifts, were added to the line lists of CO, SO2, NH3, HF, HCl, OCS, and C2H2. This work describes a further expansion introduced in the HITRAN2020 edition. In particular, relevant data for the line lists of CO2, N2O, OH, H2CO, HCN, PH3, H2S, and GeH4 were added, while those for CO, SO2, and OCS were revised. The new data are based on the semiempirical models constructed on available and validated experimental measurements and theoretical predictions. These models strongly depend on the extent and quality of the available data. The paper explains how to use the online interface or the HITRAN Application Programming Interface (HAPI) to retrieve these data from the database. Examples of calculating a molecule’s spectra in a mixture of buffer-gases using HAPI are also provided. We also provide a set of Python codes allowing one to populate any line list of corresponding molecules with relevant broadening parameters.

Study on the local compressibility of (MnF6)2− centres in KNaSiF6: Mn4+ red phosphor material by analysing its pressure-induced spectral line shifts

The local linear compressibility of (MnF6)2− centres in KNaSiF6: Mn4+ red phosphor material is estimated by analysing its pressure-induced R-line red-shift. The result is confirmed by calculating the pressure-induced E(4T2)-line blue-shift. The evaluated local linear compressibility of (MnF6)2− impurity centres is much smaller than the linear compressibility of host KNaSiF6 crystal as a whole obtained from the theoretical calculation. The causes (i.e., the local compressibility of impurity cluster being smaller than the corresponding host one, and the local compressibility of the corresponding host cluster being also smaller than the compressibility of whole crystal) about the difference between the local compressibility of (MnF6)2− impurity centre and the compressibility of whole host KNaSiF6 crystal are discussed.

Pressure-induced shift of effective Ce valence, Fermi energy and phase boundaries in CeOs4Sb12

CeOs4Sb12, a member of the skutterudite family, has an unusual semimetallic low-temperature -phase that inhabits a wedge-like area of the field H—temperature T phase diagram. We have conducted measurements of electrical transport and megahertz conductivity on CeOs4Sb12 single crystals under pressures of up to 3 GPa and in high magnetic fields of up to 41 T to investigate the influence of pressure on the different H–T phase boundaries. While the high-temperature valence transition between the metallic -phase and the -phase is shifted to higher T by pressures of the order of 1 GPa, we observed only a marginal suppression of the -phase that is found below 1 K for pressures of up to 1.91 GPa. High-field quantum oscillations have been observed for pressures up to 3.0 GPa and the Fermi surface of the high-field side of the -phase is found to show a surprising decrease in size with increasing pressure, implying a change in electronic structure rather than a mere contraction of lattice parameters. We evaluate the field-dependence of the effective masses for different pressures and also reflect on the sample dependence of some of the properties of CeOs4Sb12 which appears to be limited to the low-field region.