States Of Carbon Monoxide Research Articles

Electronic structure of excited states in carbon monoxide

A general theoretical approach to modeling electronic excited states based on a non-Hermitian Hamiltonian is proposed. The proposed analytical model has several advantages. Firstly, it allows all excited states to be targeted by specifying a single excitation parameter. Consequently, all states (ground or excited) are treated equally. Secondly, it allows the consideration of excitations of any nature and power. Thirdly, it provides an estimation of the lifetime of the excited states using a unified approach. We provide a theoretical investigation of the new metastable states in carbon monoxide using this approach. Finally, the electronic structure and the decay time of the excited states in carbon monoxide are discussed.

CO spectra of the ISM in the Host Galaxies of the most luminous WISE-selected AGNs

Abstract We present observations of mid-J (J = 4–3 or J = 5–4) carbon monoxide (CO) emission lines and continuum emission from a sample of ten of the most luminous (Lbol ≥ 1014 L$\rm \odot$) Hot Dust-Obscured Galaxies (Hot DOGs) discovered by the Wide-field Infrared Survey Explorer (WISE) with redshifts up to 4.6. We uncover broad spectral lines (FWHM ≥ 400 km s−1) in these objects, suggesting a turbulent molecular interstellar medium (ISM) may be ubiquitous in Hot DOGs. A halo of molecular gas, extending out to a radius of 5 kpc is observed in W2305–0039, likely supplied by 940 km s−1 molecular outflows. W0831+0140 is plausibly the host of a merger between at least two galaxies, consistent with observations made using ionized gas. These CO(4–3) observations contrast with previous CO(1–0) studies of the same sources: the CO(4–3) to CO(1–0) luminosity ratios exceed 300 in each source, suggesting that the lowest excited states of CO are underluminous. These findings show that the molecular gas in Hot DOGs is consistently turbulent, plausibly a consequence of AGN feedback, triggered by galactic mergers.

Low-energy inelastic electron scattering from carbon monoxide: Excitation and de-excitation of the X1Σ+, a3Π, a′3Σ+, A1Π, d3Δ, e3Σ−, I1Σ− and D1Δ electronic states

Cross-sections for electronic excitation and de-excitation among the ground state and lowest-lying seven electronic excited states of carbon monoxide (CO) by low-energy electron impact are computed using the R-matrix method. The excitation cross-sections from the ground state to the electronic states a3Π, a′3Σ+ and A1Π agree with previous experimental and theoretical results. In addition, the cross-sections for the I1Σ− and D1Δ states of CO, which will cascade to CO a′3Σ+ and A1Π states, are calculated. Furthermore, in contrast to the typical increase in electronic excitation cross-sections with collision energy, the de-excitation cross-sections show a negative trend with increasing energy.

An equation of state of CO for use in planetary modeling

Although carbon monoxide (CO) is an abundant molecule and may have great importance for planetary interiors, measurements of its properties are difficult due to its extreme volatility. We calculate the equation of state for CO over a range of temperature and density that is applicable to the conditions in planetary interiors. Previous experimental and theoretical studies cover only a limited temperature–density range. Our calculations match these early results well, but now cover the full range of relevance. The method of calculation is based on the general-purpose quotidian equation of state described by More et al. (1988), which is here used in order to generate a freely downloadable look-up table to be used by the community.

Laboratory Study of the Cameron Bands, the First Negative Bands, and Fourth Positive Bands in the Middle Ultraviolet 180–280 nm by Electron Impact Upon CO

AbstractWe have analyzed medium‐resolution (full width at half maximum, FWHM = 1.2 nm), Middle UltraViolet (MUV; 180–280 nm) laboratory emission spectra of carbon monoxide (CO) excited by electron impact at 15, 20, 40, 50, and 100 eV under single‐scattering conditions at 300 K. The MUV emission spectra at 100 eV contain the Cameron Bands (CB) CO(a 3Π → X 1Σ+), the fourth positive group (4PG) CO(A 1Π → X 1Σ+), and the first negative group (1NG) CO+(B 2Σ+ → X 2Σ) from direct excitation and cascading‐induced emission of an optically thin CO gas. We have determined vibrational intensities and emission cross sections for these systems, important for modeling UV observations of the atmospheres of Mars and Venus. We have also measured the CB “glow” profile about the electron beam of the long‐lived CO (a 3Π) state and determined its average metastable lifetime of 3 ± 1 ms. Optically allowed cascading from a host of triplet states has been found to be the dominant excitation process contributing to the CB emission cross section at 15 eV, most strongly by the d 3Δ and a' 3Σ+ electronic states. We normalized the CB emission cross section at 15 eV electron impact energy by multilinear regression (MLR) analysis to the blended 15 eV MUV spectrum over the spectral range of 180–280 nm, based on the 4PG emission cross section at 15 eV that we have previously measured (Ajello et al., 2019, https://doi.org/10.1029/2018ja026308). We find the CB total emission cross section at 15 eV to be 7.7 × 10−17 cm2.

Time-resolved observation of transient precursor state of CO on Ru(0001) using carbon K-edge spectroscopy.

The transient dynamics of carbon monoxide (CO) molecules on a Ru(0001) surface following femtosecond optical laser pump excitation has been studied by monitoring changes in the unoccupied electronic structure using an ultrafast X-ray free-electron laser (FEL) probe. The particular symmetry of perpendicularly chemisorbed CO on the surface is exploited to investigate how the molecular orientation changes with time by varying the polarization of the FEL pulses. The time evolution of spectral features corresponding to the desorption precursor state was well distinguished due to the narrow line-width of the C K-edge in the X-ray absorption (XA) spectrum, illustrating that CO molecules in the precursor state rotated freely and resided on the surface for several picoseconds. Most of the CO molecules trapped in the precursor state ultimately cooled back down to the chemisorbed state, while we estimate that ∼14.5 ± 4.9% of the molecules in the precursor state desorbed into the gas phase. It was also observed that chemisorbed CO molecules diffused over the metal surface from on-top sites toward highly coordinated sites. In addition, a new "vibrationally hot precursor" state was identified in the polarization-dependent XA spectra.

Strong and selective isotope effect in the vacuum ultraviolet photodissociation branching ratios of carbon monoxide

Rare isotope (13C, 17O and 18O) substitutions can substantially change absorption line positions, oscillator strengths and photodissociation rates of carbon monoxide (CO) in the vacuum ultraviolet (VUV) region, which has been well accounted for in recent photochemical models for understanding the large isotopic fractionation effects that are apparent in carbon and oxygen in the solar system and molecular clouds. Here, we demonstrate a strong isotope effect associated with the VUV photodissociation of CO by measuring the branching ratios of 12C16O and 13C16O in the Rydberg 4p(2), 5p(0) and 5s(0) complex region. The measurements show that the quantum yields of electronically excited C atoms in the photodissociation of 13C16O are dramatically different from those of 12C16O, revealing strong isotope effect. This isotope effect strongly depends on specific quantum states of CO being excited, which implies that such effect must be considered in the photochemical models on a state by state basis.

Iron(II)porphyrin-Cyclodextrin Supramolecular Complex as a Carbon Monoxide-Depleting Agent in Living Organisms.

The specific intermolecular interaction between an anionic tetraarylporphyrin and per-O-methylated β-cyclodextrin (TMe-β-CD) paved the way to produce a functional supramolecule that works as a strong carbon monoxide (CO)-depleting agent in living organisms. The supramolecular complex, hemoCD, that is composed of meso-tetrakis(4-sulfonatophenyl)porphinatoiron(II) and a TMe-β-CD dimer linked by a pyridine linker, captured internal CO from carboxyhemoglobin during its circulation in the blood of animals. HemoCD thus produced the pseudo-knockdown (loss-of-functional) state of endogenous CO in the animals. This unique property led us to investigate the biological function of endogenous CO as a gaseous signal mediator in living systems. In this paper, we introduce our recent study on the hemoCD complex as a biological CO-depleting agent.

Feedback Response to Selective Depletion of Endogenous Carbon Monoxide in the Blood.

The physiological roles of endogenous carbon monoxide (CO) have not been fully understood because of the difficulty in preparing a loss-of-function phenotype of this molecule. Here, we have utilized in vivo CO receptors, hemoCDs, which are the supramolecular 1:1 inclusion complexes of meso-tetrakis(4-sulfonatophenyl)porphinatoiron(II) with per-O-methylated β-cyclodextrin dimers. Three types of hemoCDs (hemoCD1, hemoCD2, and hemoCD3) that exhibit different CO-affinities have been tested as CO-depleting agents in vivo. Intraperitoneally administered hemoCD bound endogenous CO within the murine circulation, and was excreted in the urine along with CO in an affinity-dependent manner. The sufficient administration of hemoCD that has higher CO-affinity than hemoglobin (Hb) produced a pseudoknockdown state of CO in the mouse in which heme oxygenase-1 (HO-1) was markedly induced in the liver, causing the acceleration of endogenous CO production to maintain constant CO-Hb levels in the blood. The contents of free hemin and bilirubin in the blood plasma of the treated mice significantly increased upon removal of endogenous CO by hemoCD. Thus, a homeostatic feedback model for the CO/HO-1 system was proposed as follows: HemoCD primarily removes CO from cell-free CO-Hb. The resulting oxy-Hb is quickly oxidized to met-Hb by oxidant(s) such as hydrogen peroxide in the blood plasma. The met-Hb readily releases free hemin that directly induces HO-1 in the liver, which metabolizes the hemin into iron, biliverdin, and CO. The newly produced CO binds to ferrous Hb to form CO-Hb as an oxidation-resistant state. Overall, the present system revealed the regulatory role of CO for maintaining the ferrous/ferric balance of Hb in the blood.

State-averaged Monte Carlo configuration interaction applied to electronically excited states

We introduce state-averaging into the method of Monte Carlo configuration interaction (SA-MCCI) to allow the stable and efficient calculation of excited states. We show that excited potential curves for H3, including a crossing with the ground state, can be accurately reproduced using a small fraction of the full configuration interaction (FCI) space. A recently introduced error measure for potential curves [J. P. Coe and M. J. Paterson, J. Chem. Phys. 137, 204108 (2012)] is also shown to be a fair approach when considering potential curves for multiple states. We demonstrate that potential curves for LiF using SA-MCCI agree well with the FCI results and the avoided crossing occurs correctly. The seam of conical intersections for CH2 found by Yarkony [J. Chem. Phys. 104, 2932 (1996)] is used as a test for SA-MCCI and we compare potential curves from SA-MCCI with FCI results for this system for the first three triplet states. We then demonstrate the improvement from using SA-MCCI on the dipole of the 2 (1)A1 state of carbon monoxide. We then look at vertical excitations for small organic molecules up to the size of butadiene where the SA-MCCI energies and oscillator strengths are compared with CASPT2 values [M. Schreiber, M. R. Silva-Junior, S. P. A. Sauer, and W. Thiel, J. Chem. Phys. 128, 134110 (2008)]. We finally see if the SA-MCCI results for these excitation energies can be improved by using MCCIPT2 with approximate natural orbitals when the PT2 space is not onerously large.

Improved intraischemic perfusion and pial arteriolar dilation by transfusion of pegylated hemoglobin in the carbon monoxide state

Transfusion of chemically‐modifed, cell‐free hemoglobin (Hb) during middle cerebral artery occlusion (MCAO) can reduce infarct volume, but large amounts are typically required. We tested the concept that transfusion of Hb in the CO state would promote vasodilation during MCAO without requiring large amounts of Hb to be transfused. Transfusion of 10 ml/kg of a 4% solution of pegylated COHb (PEG‐COHb) in anesthetized rats resulted in rapid release of CO and equilibration of CO with red cell‐based Hb (2–3% COHb in whole blood and plasma). Plasma [Hb] was ~0.5 g/dL. Induction of MCAO initially produced 37±8% (±SD) dilation of pial arterioles in the MCA border region that gradually subsided to 7±7% at 2 h in controls. Transfusion of PEG‐COHb at 20 min of MCAO maintained pial arterioles in a dilated state (40±13%) at 2 h, whereas transfusion of albumin (25±13%) or PEG‐Hb without CO (22±8%) had intermediate effects. When transfusion of PEG‐COHb was delayed by 90 min, penumbral laser‐Doppler flow increased from 58% to 80% of pre‐ischemic baseline, whereas transfusion of albumin or PEG‐Hb produced no significant change. We conclude that PEG‐COHb can serve as a CO donor that effectively prevents time‐dependent loss of pial arteriolar dilation during MCAO and improves blood flow in the penumbral region to levels above the threshold typically associated with eventual infarction. (Supported by NIH NS38684).

Cross section and rate coefficient calculations for electron impact excitation of the a $^{\sf 3}{\sf \Pi}$ , a’ $^{\sf 3}{\sf \Sigma^{+}}$ , d $^{\sf 3}{\sf \Delta}$ , e $^{\sf 3}{\sf \Sigma^{-}}$ , I $^{\sf 1}{\sf \Sigma^{+}}$ and D $^{\sf 1}{\sf \Delta}$ states of CO

An efficient theoretical method for investigating the cross sections and rate coefficients of electron impact excitation processes involving carbon monoxide (CO) diatomic molecules has been applied in the temperature range 1500–15 000 K. The weighted total cross section (WTCS) theory has been used to investigate the cross sections excitation of the a 3Π, a’ 3Σ+, d 3Δ, e 3Σ-, I 1Σ+ and D 1Δ states of CO. The 300 K cross sections as a function of electron energy and one temperature rate coefficients results are presented and fitting parameters (a, b and c) are given for each reaction rate coefficient: k(θ) = a (θb) exp (-c/θ).

Ligand Migration and Cavities within Scapharca Dimeric HbI: Studies by Time-Resolved Crystallo- graphy, Xe Binding, and Computational Analysis

As in many other hemoglobins, no direct route for migration of ligands between solvent and active site is evident from crystal structures of Scapharca inaequivalvis dimeric HbI. Xenon (Xe) and organic halide binding experiments, along with computational analysis presented here, reveal protein cavities as potential ligand migration routes. Time-resolved crystallographic experiments show that photodissociated carbon monoxide (CO) docks within 5 ns at the distal pocket B site and at more remote Xe4 and Xe2 cavities. CO rebinding is not affected by the presence of dichloroethane within the major Xe4 protein cavity, demonstrating that this cavity is not on the major exit pathway. The crystal lattice has a substantial influence on ligand migration, suggesting that significant conformational rearrangements may be required for ligand exit. Taken together, these results are consistent with a distal histidine gate as one important ligand entry and exit route, despite its participation in the dimeric interface.

Excitation of theCΣ+1+cΠ3andEΠ1electronic states of carbon monoxide by electron impact

We report differential cross-section measurements for electron-impact excitation of the $C\phantom{\rule{0.2em}{0ex}}^{1}\ensuremath{\Sigma}^{+}+c\phantom{\rule{0.2em}{0ex}}^{3}\ensuremath{\Pi}$ and $E\phantom{\rule{0.2em}{0ex}}^{1}\ensuremath{\Pi}$ electronic states in carbon monoxide. The energy range of this work is $30--200\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. Where a comparison is possible, reasonable agreement is found with the earlier $20--50\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ results from Middleton et al. [J. Phys. B 26, 1743 (1993)]. A generalized oscillator strength analysis of the present differential cross-section data enables us to determine estimates of the corresponding integral cross sections, which are compared to results from the $\mathrm{BE}f$-scaling approach [Y.-K. Kim, J. Chem. Phys. 126, 064305 (2007)] calculated as a part of this study. Very good agreement between them is in general found. Finally our $100\text{\ensuremath{-}}\mathrm{eV}$ and $200\text{\ensuremath{-}}\mathrm{eV}$ generalized oscillator strength data are also employed to determine values of the respective $C\phantom{\rule{0.2em}{0ex}}^{1}\ensuremath{\Sigma}^{+}$ and $E\phantom{\rule{0.2em}{0ex}}^{1}\ensuremath{\Pi}$ optical oscillator strengths, with excellent agreement being found between them and the previous dipole $(e,e)$ results from Chan et al. [Chem. Phys. 170, 123 (1993)].

Superexcited states of carbon monoxide studied by fast-electron impact

Absolute optical oscillator strength density and double differential cross section spectra of CO below 120 eV are determined by fast electron impact. Some peaks above the first ionization threshold stand out as the momentum transfer square K2 increases. The doubly excited Rydberg states converging to C 2Σ+, D 2Π and F 2Π states of CO+, respectively, are confirmed in our spectra. Another peak at around 32 eV is assigned to the transition of (3σ)−1(2π)1 1Π← X1Σ+.

On the c3Π ( v = 0) state of carbon monoxide

A full analysis of the near infrared c 3Π– b 3Σ + (0–0) band is given and term values for both states determined. The c 3Π ( v = 0) state was jointly analysed with the perturbing k 3Π ( v = 2) state and data from the c 3Π– X 1Σ + (0–0) transition and 3 A band system were included. It is shown that the available data are consistent with the c 3Π ( v = 0) state having near Hund’s case b coupling with a spin–orbit constant of A = 0.45 ± 0.02 cm −1, a homogeneous perturbation with the k 3Π ( v = 2) state, and Λ-type doubling arising predominantly from its interaction with the j 3Σ + state. A discrepancy with a more recent report of the 3 A band system is identified and discussed. The perturbed b 3Σ + state term values are consistent with a previously reported five state interaction model.

Neutral dissociation of superexcited states in carbonmonoxide

Neutral photodissociation of CO has been investigated usingsynchrotron light in the range 19-26 eV by observing dispersedfluorescence from excited neutral C atoms. Follow-up abinitio calculations support the observed neutral carbon excitation functions, which to a large extent are associatedwith the CO Rydberg series converging to the CO+ C and Dstates.

Predissociation in the E 1Π, v=1 state of the six natural isotopomers of CO

The E 1Π, v=1 state of carbon monoxide is studied in high resolution using a tunable and narrowband laser source in the vacuum ultraviolet near 105 nm. Calibration with respect to a reference standard consisting of iodine lines in the visible range, measured by saturated absorption spectroscopy, yields an absolute accuracy of 0.003 cm−1 for the CO resonances. Transition frequencies of the E–X(1,0) band were determined for all six natural isotopomers (12C16O, C1712O, C1812O, C1613O, C1713O, and C1813O) and improved molecular constants derived. Natural lifetime broadening, caused by predissociation was investigated quantitatively for single rotational and (e)–(f ) parity levels. The accidental predissociation phenomena, giving rise to line shifts and broadening, could be explained up to the experimental accuracy in a model based on spin–orbit-coupling between E 1Π, v=1 and k 3Π, v=6 states, with a coupling constant of HE,k=1.88±0.01 cm−1 for all six isotopomers. The overall line broadening parameter ΓE for the E state, ascribed to interaction with a repulsive Π1 state, and Γk for the k state, were determined as well; the predissociation rates were found to decrease with increasing reduced mass of the isotopomers for both E 1Π, v=1 and k 3Π, v=6 states.

Angle-resolved spectator decay of vibrationally selected C 1s(2σ)−12π1 excited states in carbon monoxide

The decay of the C 1s(2σ) −1 2π 1 (ν′=0) and (ν′=1) vibrationally excited states in CO has been studied, in particular, the spectator decay region. The deexcitation spectra of the core-excited states have been recorded with both vibrational and angular resolution in order to guide in the assignment of the two-hole one-particle (2h1e) final states. Lifetime vibrational interference (LVI) influences the spectral features and LVI calculations have been employed to analyze the complicated vibrational structure of the overlapping electronic states. Also other states, which have been hitherto unobserved in the direct valence photoelectron spectra, are revealed.

The vibrationally resolved participator Auger spectra of selectively excited C 1s(2σ)−12π1 vibrational states in carbon monoxide

The fully vibrationally resolved participator Auger spectra originating from the decay of the C 1s(2σ)−12π1 resonance in CO are presented. The C 1s(2σ)−12π1 v′=0 resonance has been excited with a 75 meV monochromator bandpass, i.e., in Auger resonant Raman conditions, and the participator Auger spectrum observed. The C 1s(2σ)−12π1 v′=1 resonance is also excited and the corresponding participator Auger spectrum observed with a monochromator bandpass slightly larger than the inherent width. The results are compared to theoretical simulations using coherent lifetime-vibrational interference theory which accounts for the details of the spectrum. We have observed an interference shift on the transitions to different vibrational sublevels in the final state. A high resolution C 1s photoelectron spectrum of CO is also presented. The lifetime width of the C 1s core–hole state is determined to be 97(10) meV, whereas the C 1s(2σ)−12π1 resonance is measured to have a width of 86(10) meV.