Molecular Cross Sections Research Articles

The Impact of Extended H2O Cross Sections on Temperate Anoxic Planet Atmospheres: Implications for Spectral Characterization of Habitable Worlds

JWST has created a new era of terrestrial exoplanet atmospheric characterization, and with it, the possibility to detect potential biosignature gases like CH4. Our interpretation of exoplanet atmospheric spectra, and the veracity of these interpretations, will be limited by our understanding of atmospheric processes and the accuracy of input modeling data. Molecular cross sections are essential inputs to these models. The photochemistry of temperate planets depends on photolysis reactions whose rates are governed by the dissociation cross sections of key molecules. H2O is one such molecule; the photolysis of H2O produces OH, a highly reactive and efficient sink for atmospheric trace gases. We investigate the photochemical effects of improved H2O cross sections on anoxic terrestrial planets as a function of host star spectral type and CH4 surface flux. Our results show that updated H2O cross sections, extended to wavelengths >200 nm, substantially impact the predicted abundances of trace gases destroyed by OH. The differences for anoxic terrestrial planets orbiting Sun-like host stars are greatest, showing changes of up to 3 orders of magnitude in surface CO levels, and over an order of magnitude in surface CH4 levels. These differences lead to observable changes in simulated planetary spectra, especially important in the context of future direct-imaging missions. In contrast, the atmospheres of planets orbiting M-dwarf stars are substantially less affected. Our results demonstrate a pressing need for refined dissociation cross-section data for H2O, where uncertainties remain, and other key molecules, especially at mid-UV wavelengths >200 nm.

Theoretical study of a new molecular ion species BeN+: molecular states and cross sections for electronic excitation and dissociation.

We present here a theoretical study of a new molecular ion species BeN+, which has not been reported before. Using a good quality configuration interaction model, we first undertake a configuration interaction calculation of the molecular states to obtain the potential energy curves of several low lying states of BeN+ and the dipole and transition dipole moments of some of its states as a function of the internuclear distance. We find the ground state to be bound and of X 3Σ- character having a shallow minimum at Re = 2.9031a0 and several other closely spaced excited states some of which are repulsive. We have determined the spectroscopic parameters for some of these states by fitting the raw potential energy data to a 6-parameter analytical potential energy function. Subsequently, the R-matrix method is used to obtain electron collision cross sections for electronic excitation from the ground X 3Σ- state to several of its excited states at the equilibrium Re = 2.9031a0 and cross sections for electron impact dissociation. We have also reported many Feshbach resonances and their widths at the equilibrium Re = 2.9031a0, which may, in future studies, be extended to potential energy curves for neutral dissociative states. The states and cross sections obtained are of considerable significance for edge plasma chemistry in fusion devices operating with beryllium walls.

ÆSOPUS 2.0: Low-temperature Opacities with Solid Grains

Abstract In this study we compute the equation of state and Rosseland mean opacity from temperatures of T ≃ 30,000 K down to T ≃ 400 K, pushing the capabilities of the ÆSOPUS code into the regime where solid grains can form. The GGchem code is used to solve the chemistry for temperatures less than ≃3000 K. Atoms, molecules, and dust grains in thermodynamic equilibrium are all included in the equation of state. To incorporate monochromatic atomic and molecular cross sections, an optimized opacity sampling technique is used. The Mie theory is employed to calculate the opacity of 43 grain species. Tables of Rosseland mean opacities for scaled-solar compositions are provided. Based on our computing resources, opacities for other chemical patterns, as well as various grain sizes, porosities, and shapes, can be easily computed upon user request to the corresponding author.

Tiresia: A code for molecular electronic continuum states and photoionization

The Tiresia program [1] provides access to numerically accurate solutions of the one-particle Schrödinger equation for highly excited states of complex polyatomic molecules, both bound and continuum, that cannot be described by conventional Quantum Chemistry approaches. It is based on an expansion of the required solution in a local multicentric basis set, with primitive functions built as products of a radial B-spline times a real spherical harmonic. In conjunction with Density Functional Theory (DFT), it has been extensively employed in a large variety of photoionization studies, also for rather large systems. Highly excited bound states as well as wavepacket propagation can also be accurately described. In fact, the flexibility of the basis essentially allows accurate solutions of linear operator equations, like Poisson or inhomogeneous perturbative equations, which are employed in the code. The program is parallelized with standard MPI-I instructions and makes extensive use of the Scalapack linear algebra library. Ancillary programs are available for the evaluation of photoionization cross sections and angular distributions from randomly to fully oriented molecules. Program summaryProgram Title: TiresiaCPC Library link to program files:https://doi.org/10.17632/fcrjxwgjxh.1Licensing provisions: GPLv3Programming language: Fortran77, Fortran90, MPISupplementary material: Program manual documentNature of problem: Accurate solutions for highly excited and continuum electronic states in complex polyatomic molecules. Molecular photoionization cross sections and angular distributions under high energy, high-intensity radiation pulses from Synchrotron radiation and laser sources, photoelectron imaging in pump-probe experiments, basis for electronic wavepackets under ultrafast or nonperturbative excitation.Solution method: Solution of the Schrödinger and similar linear operator equations in a finite domain is obtained via basis set expansion. Flexible basis set, that may approach practical completeness within the domain, is obtained as a multicenter set of B-spline radial functions times spherical harmonics. Accurate numerical integration is employed for the evaluation of matrix elements, and conventional diagonalization for bound states, or Galerkin approach for the full multichannel solution in the continuum. Full hamiltonian and dipole matrices in the spectral basis are available for time propagation. DFT many-body description is available, and strong correlations in the bound states may be incorporated via Dyson orbitals.Additional comments including restrictions and unusual features: The code is noted for computational efficiency, which allows fast yet reasonably accurate photoionization calculations for medium-sized molecules, allowing, e.g., calculations at many molecular geometries as required to describe time-resolved photoelectron spectra in pump-probe experiments.

Molecular electronic stopping cross section for H and He beams colliding with water: projectile charge state contribution

Abstract When an ion beam impinges on a target material, electron stripping and capture processes involve different charge fraction states in the beam, such that each projectile charge state produces a different energy-loss. In this work, the energy deposition of swift hydrogen and helium ion beams colliding with a water target in the gas phase is studied. The electronic structure of the molecular target is represented in terms of core, bond, and lone pair orbital decomposition within a Harmonic Oscillator representation. In this way, the stopping cross section becomes only a function of the orbital mean excitation energy, I 0i . The ion beam charge fraction compositions colliding on water is determined from the work of Wedlund et al (2019) Astronomy & Astrophysics, 630, A36) by accounting for the electron transfer cross sections. We find that the larger the projectile charge state, the larger the electronic stopping cross section and that the beam charge fraction determines the position of the maximum of the electronic stopping curve. Also, in agreement with the experiment, evidence is given on the dominant role of the largest projectile charge state in defining the stopping cross section for high energy collisions, while for low collision energies it is the lowest charge state together with all possible charge states contributing at the maximum of the electronic stopping cross section curve. Our results are reported and compared to available experimental data showing an excellent agreement to the available literature.

Charge Transfer and Level Lifetime in Molecular Photon-Absorption upon the Quantum Impedance Lorentz Oscillator.

On the strength of the new quantum impedance Lorentz oscillator (QILO) model, a charge-transfer method in molecular photon-absorption is proposed and imaged via the numerical simulations of 1- and 2-photon-absorption (1PA and 2PA) behaviors of the organic compounds LB3 and M4 in this paper. According to the frequencies at the peaks and the full width at half-maximums (FWHMs) of the linear absorptive spectra of the two compounds, we first calculate the effective quantum numbers before and after the electronic transitions. Thus, we obtain the molecular average dipole moments, i.e., 1.8728 × 10-29 C·m (5.6145 D) for LB3 and 1.9626 × 10-29 C·m (5.8838 D) for M4 in the ground state in the tetrahydrofuran (THF) solvent. Then, the molecular 2PA cross sections corresponding to wavelength are theoretically inferred and figured out by QILO. As a result, the theoretical cross sections turn out to be in good agreement with the experimental ones. Our results reveal such a charge-transfer image in 1PA near wavelength 425 nm, where an atomic electron of LB3 jumps from the ground-state ellipse orbit with the semimajor axis ai = 1.2492 × 10-10m = 1.2492 Å and semiminor axis bi = 0.4363 Å to the excited-state circle (aj = bj = 2.5399 Å). In addition, during its 2PA process, the same transitional electron in the ground state is excited to the elliptic orbit with aj = 2.5399 Å and bj =1.3808 Å, in which the molecular dipole moment reaches as high as 3.4109 × 10-29 C·m (10.2256 D). In addition, we obtain a level-lifetime formula with the microparticle collision idea of thermal motion, which indicates that the level lifetime is proportional (not inverse) to the damping coefficient or FWHM of an absorptive spectrum. The lifetimes of the two compounds at some excited states are calculated and presented. This formula may be used as an experimental method to verify 1PA and 2PA transition selection rules. The QILO model exhibits the advantage of simplifying the calculation complexity and reducing the high cost associated with the first principle in dealing with quantum properties of optoelectronic materials.

Calculated and Empirical Values of Vibronic Transition Dipole Moments of Reactive Chemical Intermediates for Determination of Concentrations.

Absorption spectroscopy has long been known as a technique for making molecular concentration measurements and has received enhanced visibility in recent years with the advent of new techniques, like cavity ring-down spectroscopy, that have increased its sensitivity. To apply the method, it is necessary to have a known molecular absorption cross section for the species of interest, which typically is obtained by measurements of a standard sample of known concentration. However, this method fails if the species is highly reactive, and indirect means for attaining the cross section must be employed. The HO2 and alkyl peroxy radicals are examples of reactive species for which absorption cross sections have been reported. This work explores and describes for these peroxy radicals the details of an alternative approach for obtaining these cross sections using quantum chemistry methods for the calculation of the transition dipole moment upon whose square the cross section depends. Likewise, details are given for obtaining the transition moment from the experimentally measured cross sections of individual rovibronic lines in the near-IR Ã-X̃ electronic spectrum of HO2 and the peaks of the rotational contours in the corresponding electronic transitions for the alkyl (methyl, ethyl, and acetyl) peroxy radicals. In the case of the alkyl peroxy radicals, good agreement for the transition moments, ≈20%, is found between the two methods. However, rather surprisingly, the agreement is significantly poorer, ≈40%, for the HO2 radical. Possible reasons for this disagreement are discussed.

Machine Learning for Ionization Potentials and Photoionization Cross Sections of Volatile Organic Compounds.

Molecular ionization potentials (IP) and photoionization cross sections (σ) can affect the sensitivity of photoionization detectors (PIDs) and other sensors for gaseous species. This study employs several methods of machine learning (ML) to predict IP and σ values at 10.6 eV (117 nm) for a dataset of 1251 gaseous organic species. The explicitness of the treatment of the species electronic structure progressively increases among the methods. The study compares the ML predictions of the IP and σ values to those obtained by quantum chemical calculations. The ML predictions are comparable in performance to those of the quantum calculations when evaluated against measurements. Pretraining further reduces the mean absolute errors (ε) compared to the measurements. The graph-based attentive fingerprint model was most accurate, for which εIP = 0.23 ± 0.01 eV and εσ = 2.8 ± 0.2 Mb compared to measurements and computed cross sections, respectively. The ML predictions for IP correlate well with both the measured IPs (R 2 = 0.88) and with IPs computed at the level of M06-2X/aug-cc-pVTZ (R 2 = 0.82). The ML predictions for σ correlated reasonably well with computed cross sections (R 2 = 0.66). The developed ML methods for IP and σ values, representing the properties of a generalizable set of volatile organic compounds (VOCs) relevant to industrial applications and atmospheric chemistry, can be used to quantitatively describe the species-dependent sensitivity of chemical sensors that use ionizing radiation as part of the sensing mechanism, such as photoionization detectors.

Temperature Influence on the Optical Properties, Attenuation Coefficient, and Total Molecular Cross Section of Dhunge Dhara Drinking Water

This work aims to measure the different parameters of Dhunge Dhara water (DDW) such as absorbance, transmittance, mass attenuation coefficient (MAC), and molecular cross section (MCS) and experimentally compare the obtained values with those of pure water (PW) at various temperatures (5 °C to 90 °C) using a theremino spectrometer. Observation shows that the parameters vary with temperature and wavelength. The transmittance of DDW ranges from 18% to 85% and absorbance of the same ranges from 0.09 Au to 0.7 Au. Meanwhile, the transmittance of PW ranges from 40% to 98% and the absorbance of the same ranges from 0.09 Au to 0.39 Au. The MAC of PW ranges from 0.02 cm2g−1 to 0.6 cm2g−1, and that for DDW ranges from 0.2 cm2g−1 to 1.1 cm2g−1 at 30 °C. The MCS of PW ranges from to , and that of DDW ranges from to at 30 °C. In conclusion, DDW has an extremely high amount of impurities and total dissolved solids and is recommended to be filtered prior to use (drinking and cooking)

Chemical composition of gaseous products generated by coplanar barrier discharge in air and N2/O2 mixtures

Absolute densities of gaseous products generated by coplanar dielectric barrier discharge in N2/O2 mixtures and in ambient air were determined using Fourier transform infrared (FTIR) spectroscopy. A theoretical model containing up to four molecular absorption cross sections was used to split the peaks overlapping in the FTIR spectra. The product densities were determined for a wide range of applied input powers (100–400 W). Ozone (O3) and nitrogen oxides (N2O, NO, NO2 and N2O5) were identified as the stable products of the discharge in N2/O2 mixtures, HNO2, HNO3 and CO2 were steadily present in the gas coming from the discharge in ambient air. It was found that the actual product composition strongly depends on the gas temperature. At low input power with the low gas temperature, O3 density was high and the NO and NO2 densities were very low. At a specific input power (and the gas temperature) O3 disappeared, while NO density started to increase gradually and NO2 density increased steeply. N2O5 density increased at low input power but decreased suddenly at the same temperature when O3 density decreased. The influence of the gas temperature on the discharge product composition was also confirmed by the 0D chemical kinetic model and by temperature measurement. The maximal ozone density reached approximately 2.7 × 1023 m−3 for the input power below 150 W and the gas mixture N2:O2 40:60. Density of 2.6 × 1022 m−3 was obtained for NO2 in the same gas mixture above 250 W.

Photonic Impacts on Photosynthesis Phenomena Based On Crops Leaves

The objective of this work is to study the photonic force and impulses on a leaf, intensity after passing through the leaf, and molecular cross-section chlorophyll of the leaf. To study we use analytical and computational methods. The observation shows that photonic force and impulse on leaves of crops decrease with wavelength, intensity also decreases with the thickness of leaves and molecular cross-section of Chlorophyll a type is lesser than Chlorophyll b type. A study of this parameter shows the huge impact on the photosynthesis phenomena of plants which further disturbed the growth of plants in different parts of their body. With the study, it is also found that the spectrum of the visible range is suitable for the photosynthesis process because the energy gap of Chlorophyll a type and Chlorophyll b type lie in the visible spectrum region. In addition, the higher energy spectrum damages the photosynthesis process by damaging Chlorophyll a and Chlorophyll b. Hence, this study shows how the force, impulse, intensity, and molecular cross section affect the photosynthesis process and diet of plants which is related to leaves.

Molecular networking and collision cross section prediction for structural isomer and unknown compound identification in plant metabolomics: a case study applied to Zhanthoxylum heitzii extracts

Mass spectrometry-based plant metabolomics allow large-scale analysis of a wide range of compounds and the discovery of potential new active metabolites with minimal sample preparation. Despite recent tools for molecular networking, many metabolites remain unknown. Our objective is to show the complementarity of collision cross section (CCS) measurements and calculations for metabolite annotation in a real case study. Thus, a systematic and high-throughput investigation of root, bark, branch, and leaf of the Gabonese plant Zhanthoxylum heitzii was performed through ultra-high performance liquid chromatography high-resolution tandem mass spectrometry (UHPLC-QTOF/MS). A feature-based molecular network (FBMN) was employed to study the distribution of metabolites in the organs of the plants and discover potential new components. In total, 143 metabolites belonging to the family of alkaloids, lignans, polyphenols, fatty acids, and amino acids were detected and a semi-quantitative analysis in the different organs was performed. A large proportion of medical plant phytochemicals is often characterized by isomerism and, in the absence of reference compounds, an additional dimension of gas phase separation can result in improvements to both quantitation and compound annotation. The inclusion of ion mobility in the ultra-high performance liquid chromatography mass spectrometry workflow (UHPLC-IMS-MS) has been used to collect experimental CCS values in nitrogen and helium (CCSN2 and CCSHe) of Zhanthoxylum heitzii features. Due to a lack of reference data, the investigation of predicted collision cross section has enabled comparison with the experimental values, helping in dereplication and isomer identification. Moreover, in combination with mass spectra interpretation, the comparison of experimental and theoretical CCS values allowed annotation of unknown features. The study represents a practical example of the potential of modern mass spectrometry strategies in the identification of medicinal plant phytochemical components.

In Silico Collision Cross Section Calculations to Aid Metabolite Annotation

The interpretation of ion mobility coupled to mass spectrometry (IM-MS) data to predict unknown structures is challenging and depends on accurate theoretical estimates of the molecular ion collision cross section (CCS) against a buffer gas in a low or atmospheric pressure drift chamber. The sensitivity and reliability of computational prediction of CCS values depend on accurately modeling the molecular state over accessible conformations. In this work, we developed an efficient CCS computational workflow using a machine learning model in conjunction with standard DFT methods and CCS calculations. Furthermore, we have performed Traveling Wave IM-MS (TWIMS) experiments to validate the extant experimental values and assess uncertainties in experimentally measured CCS values. The developed workflow yielded accurate structural predictions and provides unique insights into the likely preferred conformation analyzed using IM-MS experiments. The complete workflow makes the computation of CCS values tractable for a large number of conformationally flexible metabolites with complex molecular structures.

Specific Ion Effects in Lanthanide-Amphiphile Structures at the Air-Water Interface and Their Implications for Selective Separation.

The use of surfactants to attract dissolved ions to water surfaces and interfaces is an essential step in both solvent-based and solvent-free separation processes. We have studied the interactions of lanthanide ions in the aqueous subphase with monolayers of dihexadecyl phosphate at air-water interfaces. With heavier lanthanides (atomic number Z ≥ 65) in the subphase, the floating layer can be compressed to an area/molecule of about half the molecular cross section, indicating bilayer formation. X-ray fluorescence and reflectivity data support this conclusion. In the presence of lighter lanthanides (Z < 65), only monolayers are observed. Subphase-concentration-dependent studies using Er3+ (heavier) and Nd3+ (lighter) lanthanides show a stepwise progression, with ions attaching to the monolayer only when the solution concentration is >3 × 10-7 M. Above ∼10-5 M, bilayers form but only in the presence of the heavier lanthanide. Grazing incidence X-ray diffraction shows evidence of lateral ion-ion correlations in the bilayer structure but not in monolayers. Explicit solvent all-atom molecular dynamics simulations confirm the elevated ion-ion correlation in the bilayer system. This bilayer structure isolates heavier lanthanides but not lighter lanthanides from an aqueous solution and is therefore a potential mechanism for the selective separation of heavier lanthanides.

Raman efficiency in the middle ultraviolet band for G‐series nerve agents and sulfur mustard

AbstractRaman spectroscopy has proven useful for chemical agent detection, but the wavelength‐dependent scattering cross section and absorption, as well as induced fluorescence, usually affects the sensitivity. Ultraviolet (UV) wavelength excitation is investigated as a method to increase the efficiency and possibly enhance the applicability for detection of contamination on surfaces from a distance, potentially including an imaging capability. With this aim, we have measured UV Raman spectra and their strength as a function of laser wavelength in a range from 210 to 330 nm using a tunable pulsed laser and a response calibrated spectroscopic system. Results from small droplets of the low volatile chemical warfare agents, GA (tabun), GF (cyclosarin), sulfur mustard (HD), and the agent simulant tributyl phosphate (TBP) applied to silicon wafer surfaces are reported. Particular emphasis is put on the radiative ratio of observed Raman scattering to laser excitation, quantified as the Raman target efficiency. Measured absorption cross sections were used to estimate the effective optical depth and molecular Raman cross sections as a function of wavelength. In addition, a secondary optical probe and spectrometer were used to monitor any induced fluorescence.

On the BET Surface Area of Nanocellulose Determined Using Volumetric, Gravimetric and Chromatographic Adsorption Methods

Volumetric N2 adsorption at −196°C is generally accepted as “gold standard” for estimating the Brunauer-Emmet-Teller (BET) surface area of nanocellulose. It is unclear however, whether the BET surface area of nanocellulose obtained at such low temperatures and pressures is meaningful at an absolute sense, as nanocellulose is used at ambient temperature and pressure. In this work, a systematic evaluation of the BET surface area of nanocellulose using highly crystalline bacterial cellulose (BC) as model nanocellulose was undertaken to achieve a comprehensive understanding of the limitations of BET method for nanocellulose. BET surface area obtained using volumetric N2 adsorption at −196°C was compared with the BET surface area acquired from gravimetric experiments based on n-octane adsorption using dynamic vapour sorption (DVS) and n-octane adsorption determined by inverse gas chromatography (iGC), both at 25°C. It was found that the BET surface area calculated from volumetric N2 adsorption data was 25% lower than that of n-octane adsorption at 25°C obtained using DVS and iGC adsorption methods. These results supported the hypothesis that the BET surface area of nanocellulose is both a molecular scale (N2vs n-octane, molecular cross section of 0.162 nm2vs 0.646 nm2) and temperature (−196°C vs 25°C) dependent property. This study also demonstrates the importance of selecting appropriate BET pressure range based on established criteria and would suggest that room temperature measurement is more relevant for many nanocellulose applications.

A database of electron-impact ionization cross sections of molecules composed of H, C, N, O, and F

Electron-impact ionization cross sections are essential parameters required in various plasma models. To provide self-consistent ionization cross sections in plasma modeling, an open database with tabular fitting parameters and an online web system are established in this work. There are 88 species composed of H, C, N, O, and F in this database. The Binary-Encounter-Bethe (BEB) model, the Deutsch-Märk (DM) model, and the combined model which consolidates the BEB and DM models are considered to obtain the atomic and molecular ionization cross sections. The input parameters of the above models for all the species are calculated according to the quantum chemical computation with the hybrid density functional theory method with the Austin–Petersson–Frisch functional including dispersion. The same methods and basis set ensure consistent ionization cross sections in the database. The average relative error between the calculated and experimental ionization potential is 1.84%. The average root-mean-square error of the fitted ionization cross sections is 1.81% with respect to the exact values predicted by the combined model. The online database can be accessed from the website http://plasma.mathboylinlin.com/db/cs/ion/.

Exploration of material characteristics of tantalum borosilicate glasses by experimental, simulation, and theoretical methods

We aimed to perform a multimethod characterization of the nuclear shielding ability of some tantalum borosilicate glasses. Accordingly, gamma-ray attenuation parameters of glasses with the nominal composition of xTa2O5-(50-x)BaO–25B2O3–15SiO2–10CaO (x = 0, 4, 8, 12, and 15 wt%) were extensively evaluated by experimental, simulation, and theoretical methods. Firstly, amorphous structures of the glasses were determined by X-ray diffraction measurements. The linear attenuation coefficients of the glasses were experimentally measured with a NaI (Tl) (7.62 cm × 7.62 cm) detector. Accordingly, the values obtained were compared with the program XCOM and the general-purpose Monte Carlo simulation code FLUKA at photon energies from 81 to 2614 keV along with gamma-ray transmission values. Furthermore, linear attenuation coefficients were used to calculate other related parameters, such as mass attenuation coefficients, half-value layers, mean free paths, effective atomic numbers and effective electron numbers, total molecular cross sections, total atomic cross sections, and radiation protection efficiency. It was found that the XCOM and FLUKA values of the shielding parameters are in satisfactory agreement with experimental values. Experimental mass attenuation coefficients at a photon energy of 662 keV were 0.075379, 0.075936, 0.076493, 0.077051, and 0.077469 cm2/g for xTa2O5-(50-x)BaO–25B2O3–15SiO2–10CaO with x = 0, 4, 8, 12, and 15 wt%, respectively, whereas effective atomic numbers were 19.27, 19.42, 19.56, 19.70, and 19.81, respectively. Among the samples examined, the highest linear attenuation coefficients, mass attenuation coefficients, and effective atomic and electron numbers, and the lowest half-value layers and mean free paths were reported for 15Ta2O5–35BaO–25B2O3–15SiO2–10CaO, with a material density of 4.610 g/cm3.

A study of dosimetric parameters of new born tissue and adult tissue of some organs

We have calculated the radiological parameters such as computerized tomography (CT) numbers effective atomic number (Zeff) and electron density (Nel) of newborn tissue and adult tissue of lung, kidney, heart and brain. Effective atomic number is computed by calculating the molecular, atomic and electronic cross section in the wide energy range of 1 keV–100 keV using WinXCOM. The new born tissue and adult tissue a very similar, but their atomic number, CT number and electron densities differs. This fact helps in the radiography and radiotherapy.

EXOPLINES: Molecular Absorption Cross-section Database for Brown Dwarf and Giant Exoplanet Atmospheres

Abstract Stellar, substellar, and planetary atmosphere models are all highly sensitive to the input opacities. Generational differences between various state-of-the-art stellar/planetary models arise primarily because of incomplete and outdated atomic/molecular line lists. Here we present a database of precomputed absorption cross sections for all isotopologues of key atmospheric molecules relevant to late-type stellar, brown dwarf, and planetary atmospheres: MgH, AlH, CaH, TiH, CrH, FeH, SiO, TiO, VO, and H2O. The pressure and temperature ranges of the computed opacities are 10−6–3000 bar and 75–4000 K, and their spectral ranges are 0.25–330 μm for many cases where possible. For cases with no pressure-broadening data, we use collision theory to bridge the gap. We also probe the effect of absorption cross sections calculated from different line lists in the context of ultrahot Jupiter and M-dwarf atmospheres. Using 1D self-consistent radiative–convective thermochemical equilibrium models, we report significant variations in the theoretical spectra and thermal profiles of substellar atmospheres. With a 2000 K representative ultrahot Jupiter, we report variations of up to 320 and 80 ppm in transmission and thermal emission spectra, respectively. For a 3000 K M-dwarf, we find differences of up to 125% in the spectra. We find that the most significant differences arise as a result of the choice of TiO line lists, primarily below 1 μm. In summary, (1) we present a database of precomputed molecular absorption cross sections, and (2) we quantify biases that arise when characterizing substellar/exoplanet atmospheres as a result of differences in the line lists, therefore highlighting the importance of correct and complete opacities for eventual applications to high-precision spectroscopy and photometry.