Spectra Of H2 Research Articles

The chemical composition of CO-rich comet C/2023 H2 (Lemmon)

We report on the composition of comet C/2023 H2 (Lemmon) (hereafter C/2023 H2) as measured with CRIRES$^+$ at VLT/ESO, under the Director Discretionary Time program: 2112.C-5015. We observed C/2023 H2 between November 24 and 27, 2023, after perihelion and during its close approach to Earth. We used three settings sampling the spectral region from approx 2.5 to 5 mu m, to search for fluorescence emission lines of H$_2$O, HCN, C$_2$H$_2$, NH$_3$, C$_2$H$_6$, H$_2$CO, CH$_3$OH, CH$_4$, and CO. C/2023 H2 spectra are dominated by signatures from hyper-volatile species, namely CO, C$_2$H$_6$, and CH$_4$, while it is particularly difficult to identify lines from less volatile species such as water or methanol. When compared to other comets, C/2023 H2 has an overall typical-to-enriched composition, with CO showing one of the highest infrared values reported so far in Solar System comets within 2 au from the Sun. In this respect, C/2023 H2 shares many similarities with C/2013 R1 (Lovejoy), C/2009 P1 (Garrad), and C/1999 T1 (McNaught-Hartley), although still being rather unique. Results from the analysis of optical spectra (approx 300 to 650 nm) obtained on November 16, 2023, using the Intermediate Dispersion Spectrograph at the Isaac Newton Telescopes are consistent with the infrared ones. Assuming that the composition of C/2023 H2 is original, this comet most likely formed in a region of the disc where CO was particularly enriched, or it could have been captured from other planetary systems forming in the Sun's birth cluster. Similarities with a few other comets suggest the existence of a sub-class of CO-enriched comets, which may be currently under-sampled. Alternatively, water sublimation may have been ineffective due to the presence of a thick dust mantle covering the nucleus surface.

Time propagation of electronic wavefunctions using nonorthogonal determinant expansions.

The use of truncated configuration interaction in real-time time-dependent simulations of electron dynamics provides a balance of computational cost and accuracy, while avoiding some of the failures associated with real-time time-dependent density functional theory. However, low-order truncated configuration interaction also has limitations, such as overestimation of polarizability in configuration interaction singles, even when perturbative doubles are included. Increasing the size of the determinant expansion may not be computationally feasible, and so, in this work, we investigate the use of nonorthogonality in the determinant expansion to establish the extent to which higher-order substitutions can be recovered, providing an improved description of electron dynamics. Model systems are investigated to quantify the extent to which different methods accurately reproduce the (hyper)polarizability, including the high-harmonic generation spectrum of H2, water, and butadiene.

Synthesis and characterization A derivative of levofloxacin and a study of its bacteriostatic activity

This study includes two newly synthesized prodrugs of Levofloxacin derivatives mono and dipeptide H2, where was the Synthesized monoPeptide as Levofloxacin-Histadine (L-H), as well as dipeptide H6 as Synthesis of diPeptide (phenylalanine- levofloxacin (GPA-L), using a Levofloxacin substituted. Spectroscopic data were studied for two derivative compounds H2 and H6 and reactivity indices were characterized using techniques FT-IR, 1H-NMR, and 13C-NMR. All the newly produced derivative compounds H2 and H6 have FT-IR spectra that share similarities in certain fingerprint-like bands and other bands. The essential functional group vibration bands. In the DMSO-d6 solvent, the compound H2, and H6 of 1H NMR spectra were studied, Typically, the fitted intensity ratio of the observed compound 1H NMR spectra gives, and the expected signals. The DMSO-d6 solvent was employed to record the 13C NMR spectra of levofloxacin derivatives H2 and H6. portrayed the 13C NMR spectra of generated compounds H1 through H6, comprised of the 13C NMR data. where done Further confirmation of the properties of the developed molecule emerged from 13C-NMR spectra. 1
 The bioactivity was studied for two derivative compounds H2 and H6 against three gram-positive and three gram-negative Bacteria. The mono and dipeptide prodrugs that are derivatives of levofloxacin have appeared to have excellent results against these Bacteria. Antibiotic susceptibility experimental findings revealed that various bacteria had taken different approaches to the tested drugs. most bacteria isolated in gram-positive and gram-negative demonstrated severe sensitivity to the generated compounds (H2 and H6). The spectral results in the FT-IR analyses as well as the nuclear magnetic resonance studies showed the high validity of the compounds formed ( H2 and H6) interaction, as well as the biological results showed a clear positive in killing bacteria of the type of Gram-negative and Gram-Positive.

Theoretical study of intramolecular effects and rotational spectra for H2–AgCl complex: A corrected intermolecular potential energy surface

An efficient model was developed by optimizing the terms of intermolecular potential and monomer rotations in the Hamiltonian, and then was applied to determine the global structures and rotational transitions of H2–AgCl complex. Based on this model, a detailed study of intramolecular effects were examined for intermolecuar vibrational modes, rotational transition frequencies, and spectroscopic parameters relative to those of rigid-rotor-approximation model. Firstly, the full-dimensional equilibrium geometry is determined to be (Re, r1e, r2e, θ1e, θ2e, φe) = (2.370 Å, 0.7785 Å, 2.2579 Å, 90.0°, 180.0°, 0.0°), and the averaged structure is determined to be (Rν, r1ν, r2ν, θ1ν, θ2ν, φν) = (2.436 Å, 0.7905 Å, 2.2604 Å, 76.4°, 172.8°, 0.0°), which are in excellent agree with the available data of experimental observations. In addition, the available transitions were accurately predicted with the maximal percentage error of 0.05%. Based on the determined spectroscopic parameters, two perpendicular bands were predicted and will be helpful to guide the further investigations in the far infrared spectral region experimentally.

A Note on Nearly Sasakian Manifolds

A class of nearly Sasakian manifolds is considered in this paper. We discuss the geometric effects of some symmetries on such manifolds and show, under a certain condition, that the class of Ricci semi-symmetric nearly Sasakian manifolds is a subclass of Einstein manifolds. We prove that a Codazzi-type Ricci nearly Sasakian space form is either a Sasakian manifold with a constant ϕ-holomorphic sectional curvature H=1 or a 5-dimensional proper nearly Sasakian manifold with a constant ϕ-holomorphic sectional curvature H>1. We also prove that the spectrum of the operator H2 generated by the nearly Sasakian space form is a set of a simple eigenvalue of 0 and an eigenvalue of multiplicity 4, and we induce that the underlying space form carries a Sasaki–Einstein structure. We show that there exist integrable distributions with totally geodesic leaves on the same manifolds, and we prove that there are no proper nearly Sasakian space forms with constant sectional curvature.

Dynamics of the H2 levels lying between the third and fourth dissociation thresholds (132 500 – 139 000 cm− 1)

The absorption spectrum of H2 at room temperature, was recorded at high resolution at the BESSY II synchrotron radiation storage ring in the 132500 – 139000 cm−1 energy range, allowing the study of the dynamics of the excited levels (npσ 1Σu+ and npπ 1Πu±) located between the H(n = 3) + H(n = 1) and H(n = 4) + H(n = 1) thresholds. Ionization anddissociation were found to compete for levels with n ≤ 8. In most cases, for the levels with n > 8, ionization is the only decay channel. The relative importance of the direct ionization, direct dissociation, autoionization and predissociation processes was evaluated for the whole energy range. From the different detected channels, and from the comparison with theoretical approaches, the main continua responsible for the predissociations were assigned to the V and to the B"B¯ states and the H(3p)/H(n = 3) ratios of the dissociation fragments from the 4pπ and 5pπ 1Πu- levels were measured. Molecular fluorescence was observed for few 1Πu- levels and the importance of its contribution is discussed.

The quasi bound spectrum of H2

We compute the radiative ro-vibrational emission spectrum of H involving quasi-bound states via a simple numerical method of resolution of the Schrödinger equation by introducing a modified effective molecular potential. The comparison of the eigenvalues obtained with our approximation and other theoretical methods based on scattering resonance properties is excellent. Electric quadrupole and magnetic dipole contributions are calculated and we confirm the previous computations of Forrey of the electric quadrupole transition Einstein coefficients. The astrophysical relevance of such quasi-bound levels is emphasized.

Latest eco-friendly avenues on hydrogen production towards a circular bioeconomy: Currents challenges, innovative insights, and future perspectives

The worldwide economic development, population expansion, and technological advancements contribute to a rise in global primary energy consumption. Since fossil fuels now provide around 85% of the energy requirement, a significant quantity of greenhouse gases is released, leading to climate change. To meet the pledges of the Paris agreement, a promising and potential alternative to fossil fuels needs to be commercialised. Therefore, numerous industries recognise hydrogen (H2) as a clean and stable energy source for decarbonisation or de-fossilisation. Around 90% of the world's H2 produced is grey in nature and produced from reforming fossil-based fuels. However, the future of H2 energy lies in its green, blue, and turquoise spectra due to the carbon capture scheme and corresponding clean and sustainable H2 production methodology. The fundamental goal of this research is to learn more about various low-carbon H2 generating systems. In comparison to fossil-based H2, green H2 is a costly option. Blue H2 offers several appealing characteristics; however, the carbon capture utilisation and storage (CCUS) technology are expensive and blue H2 is not carbon-free. The current CCUS technology can only store and catch between 80 and 95% of CO2. Further, it examines worldwide actions related to the H2 development policy. In addition, a debate based on the colour spectrum of H2 was established to classify the purity of H2 generation. Further, the existing obstacles, advancements, and future directions of low-carbon H2 production technologies, including fossil fuel-based and renewable-based H2, are explored to foster the growth of the low-carbon H2 economy.

NIR spectroscopic survey of protostellar jets in the star-forming region IC 1396N

Context. The bright-rimmed cloud IC 1396N, associated with an intermediate-mass star-forming region, hosts a number of CO, molecular hydrogen, and Herbig-Haro (HHs) outflows powered by a set of millimetre compact sources. Aims. The aim of this work is to characterise the kinematics and physical conditions of the H2 emission features spread throughout the IC 1396N region. The features appear as chains of knots with a jet-like morphology and trace different H2 outflows. We also obtain further information about (and an identification of) the driving sources. Methods. Low-resolution, long-slit near-infrared spectra were acquired with the NICS camera at the TNG telescope, using grisms KB (R ~ 1200), HK, and JH (R ~ 500). Several slit pointings and position angles were used throughout the IC 1396N region in order to sample a number of the H2 knots that were previously detected in deep H2 2.12 μm images. Results. The knots exhibit rich ro–vibrational spectra of H2, consistent with shock-excited excitation, from which radial velocities and relevant physical conditions of the IC 1396N H2 outflows were derived. These also allowed estimating extinction ranges towards several features. [Fe ii] emission was only detected towards a few knots that also display unusually high H2 1–0 S(3)/S(1) flux ratios. The obtained radial velocities confirm that most of the outflows are close to the plane of the sky. Nearby knots in the same chain often display different radial velocities, both blue–shifted and red–shifted, which we interpret as due to ubiquitous jet precession in the driving sources or the development of oblique shocks. One of the chains (strand A, i.e. knots A1 to A15) appears as a set of features trailing a leading bow-shock structure consistent with the results of 3D magneto-hydrodynamical models. The sides of the leading bow shock (A15) exhibit different radial velocities. We discuss possible explanations. Our data cannot confirm whether strands A and B have both originated in the intermediate mass young stellar object [BGE2002] BIMA 2 because a simple model of a precessing jet cannot account for their locations. Conclusions. Near-infrared spectroscopy has confirmed that most of the H2 ro-vibrational emission in IC 1396N is shock-excited rather than uv-excited in photon-dominated regions. It has shown a complex kinematical structure in most strands of emitting knots as well.

High harmonic spectra computed using time-dependent Kohn–Sham theory with Gaussian orbitals and a complex absorbing potential

High harmonic spectra for H2 and H2 + are simulated by solving the time-dependent Kohn-Sham equation in the presence of a strong laser field using an atom-centered Gaussian representation of the density and a complex absorbing potential. The latter serves to mitigate artifacts associated with the finite extent of the basis functions, including spurious reflection of the outgoing electronic wave packet. Interference between the outgoing and reflected waves manifests as peak broadening in the spectrum as well as the appearance of spurious high-energy peaks after the harmonic progression has terminated. We demonstrate that well-resolved spectra can be obtained through the use of an atom-centered absorbing potential. As compared to grid-based algorithms, the present approach is more readily extensible to larger molecules.

Threshold-ion-pair-production spectroscopy of H2S and D2S

The threshold-ion-pair-production (TIPP) spectra of H2S and D2S have been recorded in the vicinity of the and thresholds using a tunable vacuum-ultraviolet laser and cold molecular samples () in supersonic expansions. The ion-pair-production signal was found to be much stronger at the thresholds than at the thresholds. From the rotational structure of the spectra, the dominant photodissociation partial waves are determined to be those with , which indicates that dissociative Rydberg states of H2S with a linear ion core are involved in the formation of the ion-pair states. The H + +SH − ion-pair-dissociation threshold energy we derive for H2S is in excellent agreement with the value reported in an earlier TIPP-spectroscopic investigation by Shiell et al. [J. Phys. Chem. A 104 (19), 4339–4342 (2000)]. From our new values of the ion-pair-dissociation thresholds, we determine improved bond-dissociation energies and of and , respectively, where the numbers in parentheses represent an uncertainty of in units of the last digit.

Collision of protostellar jets in the star-forming region IC 1396N

Context. The bright-rimmed cloud IC 1396N is believed to host one of the few known cases where two bipolar CO outflows driven by young stellar objects collide. The CO outflows are traced by chains of knots of H2 emission, with enhanced emission at the position of the possible collision. Aims. The aim of this work is to use the proper motions of the H2 knots to confirm the collision scenario. Methods. A second-epoch H2 image was obtained, and the proper motions of the knots were determined with a time baseline of ~11 yr. We also performed differential photometry on the images to check the flux variability of the knots. Results. For each outflow (N and S), we classified the knots as pre-collision or post-collision. The axes of the pre-collision knots, the position of the possible collision point, and the axes of the post-collision knots were estimated. The difference between the proper motion direction of the post-collision knots and the position angle from the collision point was also calculated. For some of the knots, we obtained the 3D velocity using the radial velocity derived from H2 spectra. Conclusions. The velocity pattern of the H2 knots in the area of interaction (post-collision knots) shows a deviation from that of the pre-collision knots, consistent with being a consequence of the interaction between the two outflows. This favours the interpretation of the IC 1396N outflows as a true collision between two protostellar jets instead of a projection effect.

Investigation of the Characteristics of CO (1-0) Line Integrated Emission Intensity in Extragalactic Spirals

This paper aims to deal with the understanding of the properties of the molecular gas hydrogen in the extragalactic spirals sample. It is critical to make observations of CO (J = 1-0) line emission for spiral galaxies, particularly those with an energetic nucleus. In the sample of spiral galaxies compiled, a carbon monoxide CO (1-0) emission line can be observed. This sample of galaxies' gas kinematics and star-forming should be analyzed statistically utilizing appropriate atomic gas HI, molecular gas H2, infrared (1μm-1000μm), visual (at λblue-optical=4400A0), and radio spectrum (at νradio=1.4 GHz and 5GHz) databases. STATISTICA is software that allows us to perform this statistical analysis. The presence of a high scale of star formation activity in these galaxies is dependent linearly on the correlations between galactic luminosities. Our findings show that thermal radio luminosity and LFIR are closely related to CO line luminosity. Further, LCO and MH2 have a steep linear relationship, where the slope of the regression log LCO - LogMH2 equals 1. The LCO-SFR and LFIR-SFR relationship slopes are nearly linear (slope ~1), with a strong partial correlation RCO-SFR of 0.73 between LCO-SFR and a significant correlation RFIR-SFR of 0.5 between LFIR-SFR, according to the statistical analysis. The correlation between the rate of star formation (SFR) and hydrogen gas in spirals is significant in several fields of astrophysics. Hence, it is asserted that the important point of the current study is that there is a significant link between SFR and the actual amount of cold hydrogen gas (Mgas) for the simple reason that in our spiral analysis, the mean atomic cold gas amount quantity is almost 6 times greater than the molecular gaseous amount.

Room temperature measurements of the collision-induced absorption by H2+CO2 mixtures near 2.4 µm

Using a 101 m absorption path-length cell, Fourier transform spectra of H2+CO2 mixtures have been recorded at room temperature in the region around 2.4 µm. This enables to quantify the absorption induced, by collisions with CO2, in the central part of the fundamental band of H2. These measurements, which cover 39504400 cm−1 range, validate previous fully independent computations.

Absorption spectrum of H2 between the third and the fourth dissociation thresholds (132 500 – 139 000 cm−1)

Over a thousand spectral lines in the absorption spectrum of molecular hydrogen (H2) to the npσ 1Σu+ and npπ 1Πu± Rydberg levels (n ≥ 4) were measured and assigned for rotational levels with N’=0 – 4 in the spectral range between 132 500 and 139 000 cm−1. The experimental energies, the absorption cross sections, and Einstein A coefficients were compared with ab initio multi-channel quantum defect (MQDT) calculations. The assigned lines include 31P(1), 225 R(0) or P(2), 291 R(1) or P(3), 109 R(2) lines, 71 R(3) lines, and over 300 Q(1–3) lines. Transition energies were determined up to excitation energies of 139 000 cm−1 above the ground state, thereby extending earlier works and leading to several reassignments. The overall agreement between experiment and first principles calculations, without adjustable parameters, is very good in view of the multi-state interferences treated within the MQDT-framework. The line intensities in terms of Einstein A coefficients are well represented in the MQDT-framework. These line intensities follow, in general, the 1/n3 scaling behavior as characteristic in Rydberg series, but many deviations occur which are explained by MQDT. Despite the mostly very good agreement between the observations and the outcome of the MQDT calculations for both level energies and line intensities, some pronounced deviations were found which are discussed. The shortcomings of the MQDT calculations are ascribed to the treatment of the excited states in terms of a 1snp single electron configuration, therewith neglecting possible interferences with 1snf or 2s core excited states. So far, some 108 lines remained unassigned.

Simulating Raman spectra of hydrogen hydrates using first-principles path-integral ring-polymer molecular dynamics

A variant of first-principles (FP) path-integral ring-polymer molecular dynamics (RPMD) simulations was used to investigate the C0,C1, and C2 H2 hydrates at 280 K aiming at reproducing their experimental Raman spectra. We find that our implementation based on white-noise Langevin thermostat applied to the H2O sub-system only in the formulation of FP-RPMD is able to reproduce with high accuracy the characteristic features of the measured Raman spectra of H2 hydrates in all C0,C1, and C2 phases, demonstrating potential of our computational approach for investigating H-containing materials under pressure.

Rate coefficients for H2:H2 inelastic collisions in the ground vibrational state from 10 to 1000 K

Aims. In this work, we present a pruned set of state-to-state rate coefficients (STS rates) for inelastic H2:H2 collisions in the thermal range from 10 to 1000 K. The set includes all relevant rates needed for diagnostics based on the simulation of quadrupole infrared spectra of H2. Methods. The reported set was obtained from a quantum scattering close-coupling calculation employing a recent version of the MOLSCAT code, a high-level potential energy surface, and rotational energies of the H2 molecules with spectroscopic accuracy. These improvements have led to a significant increase in the accuracy with respect to previous computational results. The accuracy of the present STS rates is tested against recently reported experimental rates. Most dominant rates agree with the experiment within a 2σ uncertainty (2 to 6%). Results. In addition to the tables given in the main text, three machine-readable tables are available at the CDS. These tables include all the relevant numerical results of the paper, namely, the excitation and de-excitation STS rates for H2:H2 inelastic collisions at selected temperatures between 10 and 1000 K, and their functional description for interpolation at any intermediate temperature.

Photon-excitation photon-emission maps (PhexPhem maps) with rovibronic resolution as a data base for theory and astrophysics part I: method and first results for H2

Dispersed fluorescence of wavelengths between 75 and 180 nm has been recorded after excitation of room temperature by narrow bandwidth monochromatized synchrotron radiation. Spectra have been taken in the exciting-photon energy range between 11 and 18 eV for discrete energy steps of 2.5 meV at a bandwidth of about 10 meV. The exciting-photon energy bandwidth has been narrow enough to induce transitions between individual rovibronic states. The resolution in the dispersed fluorescence detection was partly sufficient to resolve fluorescent transitions between individual rovibronic states. The recorded intensities are presented as two-dimensional photon-excitation photon-emission (PhexPhem) maps. They give a complete overview of experimental dispersed VUV/ FUV fluorescence spectra of H2 for these excitation energies, covering excitation from to all known singly excited states. The presented proof of principle experiments show a way to generate spectroscopic reference data for theory benchmarking and the interpretation of astrophysical observations.

Role of exchange and correlation in high-harmonic generation spectra of H2, N2, and CO2: Real-time time-dependent electronic-structure approaches.

This study arises from the attempt to answer the following question: how different descriptions of electronic exchange and correlation affect the high-harmonic generation (HHG) spectroscopy of H2, N2, and CO2 molecules? We compare HHG spectra for H2, N2, and CO2 with different ab initio electronic structure methods: real-time time-dependent configuration interaction and real-time time-dependent density functional theory (RT-TDDFT) using truncated basis sets composed of correlated wave functions expanded on Gaussian basis sets. In the framework of RT-TDDFT, we employ Perdew-Burke-Ernzerhof (PBE) and long-range corrected Perdew-Burke-Ernzerhof (LC-ωPBE) functionals. We study HHG spectroscopy by disentangling the effect of electronic exchange and correlation. We first analyze the electronic exchange alone, and in the case of RT-TDDFT with LC-ωPBE, we use ω = 0.3 and ω = 0.4 to tune the percentage of long-range Hartree-Fock exchange and short-range exchange PBE. Then, we added the correlation as described by the PBE functional. All the methods give very similar HHG spectra, and they seem not to be particularly sensitive to the different description of exchange and correlation or to the correct asymptotic behavior of the Coulomb potential. Despite this general trend, some differences are found in the region connecting the cutoff and the background. Here, the harmonics can be resolved with different accuracy depending on the theoretical schemes used. We believe that the investigation of the molecular continuum and its coupling with strong fields merits further theoretical investigations in the near future.

Performance of two handheld NIR spectrometers to quantify crude protein of composite animal forage and feedstuff

<abstract> <p>Two handheld near infrared (NIR) spectrometers were used to quantify crude protein ($CP$) content of mixed forage and feedstuff composed of Sweet Bran, distiller's grains, corn silage, and corn stalk. First was a transportable spectrometer, which measured in the visible and NIR ranges (320–2500 nm) with a spectral interval of 1 nm (H1). Second was a smartphone spectrometer, which measured from 900–1700 nm with a spectral interval of 4 nm (H2). Spectral data of 147 forage and feed samples were collected by both handheld instruments and split into calibration ($n$ = 120) and validation ($n$ = 27) sets. For H1, only absorbances in the NIR region (780–2500 nm) were used in the multivariate analyses, while for H2, absorbances in the second and third overtone regions (940–1660 nm) were used. Principal component analysis (PCA) and partial least squares (PLS) regression models were developed using mean-centered data that had been preprocessed using standard normal variate (SNV) or Savitzky-Golay first derivative (SG1) or second derivative (SG2) algorithm. PCA models showed two major groups—one with Sweet Bran and distillers grains, and the other with corn silage and corn stalk. Using H1 spectra, the PLS regression model that best predicted $CP$ followed SG1 preprocessing. This model had low root mean square error of prediction ($RMSEP$ = 2.22%) and high ratio of prediction to deviation ($RPD$ = 5.24). With H2 spectra, the model best predicting $CP$ was based on SG2 preprocessing, returning $RMSEP$ = 2.05% and $RPD$ = 5.74. These values were not practically different than those of H1, indicating similar performance of the two devices despite having absorbance measurements only in the second and third overtone regions with H2. The result of this study showed that both handheld NIR instruments can accurately measure forage and feed $CP$ during screening, quality, and process control applications.</p> </abstract>