Carbonyl Sulfide Molecule Research Articles

Vibrational resonance phenomena of the OCS isotopologues studied by resummation of high-order Rayleigh–Schrödinger perturbation theory

The high-order Rayleigh–Schrödinger perturbation theory (RSPT) can be applied for studying anharmonic vibrational problem formulated with the isomorphic Hougen Hamiltonian, but the resulting series usually possess slowly convergent or even divergent behavior. This flaw can be overcome by the resummation of such series with the multi-valued Hermite–Padé approximant (HPA) that accurately reproduces variational matrix eigenvalues provided the basis set is the same. Besides, the state-to-state juxtaposition of HPA branch points can provide an accurate quantitative description of resonance phenomena. Such resummation was earlier proven to be efficient for three- and four-atomic asymmetric top molecules, as well as for linear molecules CO2 and C2H2. In the present work, this technique was systematically applied for studying vibrational resonances of practically important isotopologues of the linear carbonyl sulfide molecule (16O12C32S, 16O12C34S, 16O13C32S, 18O12C32S, 16O12C33S, 16O13C34S). The isomorphic Hamiltonians were constructed using the ab initio equilibrium geometry and quartic PES calculated at the CCSD(T)/cc-pV(Q+d)Z level. The analysis of HPA common branch points of 125 vibrational states for each isotopologue predicted comprehensive resonance pictures. These resonances reproduced most of experimentally observed couplings and indicated a possible break down of the known polyad formula P=2v1+v2+4v3. The demonstrated efficiency of this purely ab initio approach opens a perspective of further studies of resonances phenomena of new and hardly accessible molecules.

Unveiling the Quantitative Relationships between Electron Distribution and Steric Hindrance of Organic Amines and Their Reaction Rates with Carbonyl Sulfur: A Theoretical Calculation Investigation.

The removal of carbonyl sulfide (COS) commonly contained in natural gas is of great significance but still very challenging via a widely employed absorption process due to its low reactivity and solubility in various commercial solvents. Artificial intelligence (AI) is playing an increasingly important role in the exploration of desulfurization solvents. However, practically feasible AI models still lack a thorough understanding of the reaction mechanisms. Machine learning (ML) models established on chemical mechanisms exhibit enhanced chemical interpretability and prediction performance. In this study, we constructed a series of solvent molecules with varying functional groups, including linear aliphatic amines, cyclic aliphatic amines, and aromatic amines and proposed a three-step reaction pathway to dissect the effects of charge and steric hindrance of different substituents on their reaction rates with COS. Chemical descriptors, based on electrostatic potential (ESP), average local ionization energy (ALIE) theory, Hirshfeld charges, and Fukui functions, were used to correlate and predict the electrophilic reactivity of amine groups with COS. Substituents influence the reaction rate by changing the attraction interaction of amine groups to COS molecules and the electron rearrangement in the electrophilic reaction. Furthermore, they have more pronounced steric effects on the reaction rate in the linear amines. The descriptors N_ALIE and q(N) were found to be crucial in predicting the reactivity of amine groups with COS. Present study provides a comprehensive understanding of the reaction mechanisms of COS with amine compounds, offers specific chemical principles for the development of chemistry-driven ML models, sheds light on other types of electrophilic reactions occurring on amine and phosphine groups, and guides the development of chemical solvents in gas absorption processes.

Approaches for constraining uncertainty and degeneracy in geometry reconstruction of molecules from simulated Coulomb explosion data

Coulomb explosion imaging (CEI) data, consisting of atomic ion momenta, resulting from a rapid (few fs) ionization event, is typically recorded as a first step in the generation of a single molecule geometry measurement or the production of a ‘molecular movie’ that watches the evolution of an excited state geometry in time. Deriving a reliable geometry from this data is a crucial and challenging step, as unique solutions may not exist. In this work, we start by simulating the geometries of a molecule, which is out of equilibrium, the asymmetric carbonyl sulfide (OCS) molecule. We generate momentum data resulting from six-fold ionization and investigate two methods to reconstruct geometries. The first method is a look-up table, which is simple in principle but shows limitations in terms of accuracy and ability to identify multiple ‘degenerate’ solutions. The second is a new method using nonlinear constrained optimization, which shows potential for scalability to higher dimension. We investigate the possibility of identifying problematic geometry regions where different degenerate geometries can not be distinguished.

Circularly polarized attosecond light generation from OCS molecules irradiated by the combination of linear polarized infrared and orthogonal terahertz fields.

Researching ultrafast dynamics and creating coherent light sources will both benefit significantly from the establishment of polarization control in high-order harmonic generation (HHG). By employing the time-dependent density functional theory method, we investigate HHG of carbonyl sulfide molecules using a combination of a linear polarized infrared (IR) laser and a weaker orthogonal Terahertz (THz) field. Our findings show that by adjusting the amplitude of the THz field, the movement scale of electrons in the THz direction can be tuned, thereby one can control the harmonic intensity in the IR laser direction. This method allows for the creation of near-circularly polarized attosecond pulses. Furthermore, the ellipticity of the attosecond pulse may be changed by modifying the carrier-envelope phase of the IR laser pulse.

Noncovalent chalcogen and tetrel bonding interactions: Spectroscopic study of halide–carbonyl sulfide complexes

AbstractChalcogen and tetrel intermolecular bonding interactions formed between carbonyl sulfide and halide anions have been studied utilizing a combined experimental and theoretical approach. In particular, high‐level CCSD(T) energetics and experimental anion photoelectron spectroscopy have been used in order to assign the dominant binding motif exhibited in these complexes. Halide anions solvated by multiple carbonyl sulfide molecules have also been investigated in order to ascertain the effect that additional binding partners has on the strength of the noncovalent interactions. The experimental and computational results support the main binding motif of carbonyl sulfide molecules with halide anions being chalcogen bonding, both in dimer complexes and larger solvated complexes. In addition, comparison between the noncovalent interactions formed by halides with carbon disulfide, carbonyl sulfide, and carbon dioxide allows a deeper understanding of noncovalent binding strength in relation to isoelectronic species.Key points Spectroscopic and ab initio characterization of halide–carbonyl sulfide van der Waals complexes bound through chalcogen and tetrel bonding. Detailed insight into chalcogen and tetrel bond strength in the context of changing chemical environments. Effect of increasing solvation on noncovalent binding strength.

Carbonyl sulfide and dimethyl sulfide adsorption studies on novel square-octagon antimonene sheets – A first-principles study

Using the first-principles study, we studied the structural and electronic attributes of square-octagon antimonene nanosheet (so-SbNS). Firstly, the structural and thermal stability of so-SbNS is ascertained. The energy band gap of so-SbNS is recorded as 0.814 eV. Furthermore, the so-SbNS is deployed as base material to adsorb carbonyl sulfide (COS), and dimethyl sulfide (DMS) molecules. The physical adsorption of COS and DMS molecules is noticed on so-SbNS. The so-SbNS behaves as the acceptor of electrons observed from charge transfer and electron density difference results. The band structure and projected density of states changes are noticed due to COS and DMS adsorption on so-SbNS. The results convey that so-SbNS is new material towards the detection of COS and DMS molecules emitted from solid waste.

Stronger orientation of state-selected OCS molecules with relative-delay-adjusted nanosecond two-color laser pulses.

Using the all-optical molecular orientation technique with intense nonresonant two-color laser pulses, stronger molecular orientation |⟨cos θ2D⟩| ∼ 0.34 is achieved by employing the following two strategies: (1) carbonyl sulfide molecules lying in the lower rotational states are selected using a home-built molecular deflector and (2) the rising parts of the two wavelengths of the pump pulse are adjusted by introducing a Michelson-type delay line in the optical path. The achieved degree of molecular orientation is higher than that observed in the proof-of-principle experiment [Oda et al., Phys. Rev. Lett. 104, 213901 (2010)] by about an order of magnitude and the highest ever characterized directly by Coulomb explosion imaging with appropriate probe polarization.

A novel crossed-molecular-beam experiment for investigating reactions of state- and conformationally selected strong-field-seeking molecules

ABSTRACT The structure and quantum state of the reactants have a profound impact on the kinetics and dynamics of chemical reactions. Over the past years, significant advances have been achieved in the control and manipulation of molecules with external electric and magnetic fields in molecular-beam experiments for investigations of their state-, structure- and energy-specific chemical reactivity. Whereas studies for neutrals have so far mainly focused on weak-field-seeking species, we report here progress towards investigating reactions of strong-field-seeking molecules by introducing a novel crossed-molecular-beam experiment featuring an electrostatic deflector. The new setup enables the characterisation of state- and geometry-specific effects in reactions under single-collision conditions. As a proof of principle, we present results on the chemi-ionisation reaction of metastable neon atoms with rotationally state-selected carbonyl sulfide (OCS) molecules and show that the branching ratio between the Penning and dissociative ionisation pathways strongly depends on the initial rotational state of OCS.

A Terahertz Molecular Clock on CMOS Using High-Harmonic-Order Interrogation of Rotational Transition for Medium-/Long-Term Stability Enhancement

Chip-scale molecular clocks (CSMCs) perform frequency stabilization by referencing to the rotational spectra of polar gaseous molecules. With, potentially, the “atomic” clock grade stability, cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> -level volume, and <; 100-mW dc power, CSMCs are highly attractive for the synchronization of the high-speed radio access network (RAN), precise positioning, and distributed array sensing. However, the medium-/long-term stability of CSMCs is hindered by the transmission baseline tilting due to the uneven frequency response of the spectroscopic system and the molecular cell. To enhance the medium-/long-term stability, this article presents a CSMC architecture locking to the high-odd-order dispersion curve of the 231.061-GHz rotational spectral line of carbonyl sulfide (OCS) molecules, which is selected as the clock reference. A monolithic THz transceiver generates a high-precision, wavelength-modulated probing signal. Then, the wave-molecule interaction inside the molecular cell translates the frequency error between the probing signal and the spectral line center to the periodic intensity fluctuation. Finally, the CSMC locks to the third-order dispersion curve after a phase-sensitive lock-in detection. In addition, a pair of slot array couplers is employed as an effective chip-to-molecular cell interface. It leads to not only a higher SNR but also a significantly simplified CSMC package. Implemented on a 65-nm CMOS process, the high-order CSMC presents a measured Allan deviation of 4.3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-11</sup> under an averaging time of τ = 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> s while consuming 70.4-mW dc power.

A chirped pulse Fourier transform microwave spectrometer with multi-antenna detection

The construction of a new chirped pulse Fourier transform microwave (CP-FTMW) spectrometer with multiple-antenna detection (MAD) is reported. The instrument design and execution represent a completely new approach to possibly increasing sensitivity in CP-FTMW spectroscopy as it does not involve increased sampling, power, or passes of microwaves with the molecular sample. This is particularly advantageous for experiments where only one sampling point is available. The MAD-CP-FTMW or “MAD Chirp” is demonstrated on both linear molecule carbonyl sulfide (OCS) and asymmetric-top molecule 1,3-difluorobenzene (DFBZ) with detection points at the broadcast antenna as well as in the quadrature to the traditional receiving antenna. Signal-to-noise comparisons with each sample at each detection point have been made and are reported. Experiments demonstrating the signals detected in these new positions are molecular and not an artifact of a reflection are reported. Although this represents a first step to a possible new approach to addressing CP-FTMW sensitivity, no sensitivity increase based on this method is currently reported.

Adsorption of carbonyl sulfide on Pt-doped vacancy-defected SWCNT: A DFT study

Carbonyl sulfide (COS) is a dangerous gas produced from fossil fuel combustion and petrochemical procedures, so proper adsorbent and sensors are required for removal and detection. In this work, we study by Density Functional Theory methods the COS adsorption on a Pt-decorated vacancy-defected carbon nanotube, in order to evaluate the potential of this nanostructure as gas adsorbent or sensing material. First, we analyze the most stable configuration for Pt adsorption on the defective nanotube, obtaining a more favorable binding energy for a symmetric structure with equivalent CPt bonds. Next, several configurations are studied for COS adsorption on the Pt-doped nanotube. In the most stable systems, the adsorbate interacts with the Pt decoration through its C and S atoms, with adsorption energy values of about −2.7 eV. Overlap population and bonding order studies are also performed, showing a strong affinity between COS and the Pt-doped surface. Furthermore, an important electronic transfer from nanotube to the gas molecule was detected, which would indicate chemical adsorption. Density of states analysis also show a considerable stabilization of COS molecule after adsorption. Our study suggests that a Pt-doped carbon surface could act as a promising adsorbent and chemical sensor for COS gas removal or detection purposes.

Predictions of Entropy and Gibbs Energy for Carbonyl Sulfide.

Many chemical and physical equilibrium conditions can be determined from minimizing the Gibbs free energies of the system. Efficient analytical representations of the entropy and Gibbs free energy of carbonyl sulfide remain elusive in the communality of science and engineering. Here, we report two analytical representations of the entropy and Gibbs free energy for carbonyl sulfide, and the prediction procedures only involve six molecular constants of the carbonyl sulfide molecule. In the temperature range from 300 to 6000 K, the average relative deviations of the predicted molar entropy and reduced Gibbs free energy values of carbonyl sulfide from the National Institute of Standards and Technology database are arrived at 0.150 and 0.189%, respectively.

OCS-CO2 line broadening coefficients and their temperature dependences for the Earth and Venus atmospheres

Theoretical carbon dioxide broadened line widths of carbonyl sulfide molecule are reported at the room temperature for wide ranges of rotational quantum numbers (0 ≤ J ≤ 100) requested by spectroscopic databases. To get the temperature-dependence exponents, computations with the room-temperature parameters’ values are repeated for various temperatures characteristic of the Earth and Venus atmospheres. The calculations are performed by a semi-empirical method which is based on the impact theory of broadening, and includes the correction factors whose parameters can be determined by fitting the broadening or shifting coefficients to the experimental data. This approach particularly suitable for active molecules with nonzero dipole moments, which needs only a few experimental data for model parameters fitting. Since the common power law for the temperature-dependence exponents is invalid for wide temperature ranges, two separate sets of temperature exponents are provided for Earth and Venus atmospheres applications.

Molecular movie of ultrafast coherent rotational dynamics of OCS

Recording molecular movies on ultrafast timescales has been a longstanding goal for unravelling detailed information about molecular dynamics. Here we present the direct experimental recording of very-high-resolution and -fidelity molecular movies over more than one-and-a-half periods of the laser-induced rotational dynamics of carbonylsulfide (OCS) molecules. Utilising the combination of single quantum-state selection and an optimised two-pulse sequence to create a tailored rotational wavepacket, an unprecedented degree of field-free alignment, 〈cos2θ2D〉 = 0.96 (〈cos2θ〉 = 0.94) is achieved, exceeding the theoretical limit for single-pulse alignment. The very rich experimentally observed quantum dynamics is fully recovered by the angular probability distribution obtained from solutions of the time-dependent Schrödinger equation with parameters refined against the experiment. The populations and phases of rotational states in the retrieved time-dependent three-dimensional wavepacket rationalises the observed very high degree of alignment.

Chip-Scale Terahertz Carbonyl Sulfide Clock: An Overview and Recent Studies on Long-Term Frequency Stability of OCS Transitions

This paper reviews the recent innovations of a miniature time-keeping device with high affordability: chip-scale molecular clock. It is based on the recent research progress of high-precision terahertz (THz) rotational spectrometers, especially those using CMOS integrated circuit technologies. The clock probes the rotational modes of carbonyl sulfide ( <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">16</sup> O <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> C <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">32</sup> S) molecule gas and then calibrates its MHz output according to the measured terahertz transition frequency of OCS. In contrast to cesium/rubidium atomic clocks, the THz OCS clock has fully electronic operations and, hence, a significantly simplified implementation. In particular, it is realizable on a waveguide-attached CMOS chip, which minimizes the form factor and cost. Based on a lab scale prototype with an Allan deviation in the 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-11</sup> range, this paper for the first time studies two critical metrics related to the long-term stability of THz OCS clocks. These metrics are the clock sensitivities to temperature change of the OCS gas and external magnetic field. The measured average temperature coefficient of the clock, without ovenized temperature stabilization and temperature compensation, is 9.5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-11</sup> /°C in the range of 28 °C-70 °C. Next, the measured clock shift in response to a 75 G external magnetic field is <;4 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-11</sup> , with a theoretical value near 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-13</sup> . Lastly, this paper also reviews the first reported CMOS prototype of the clock, which consumes only 66 mW dc power and achieves an Allan deviation of 3.8 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-10</sup> (τ = 1000 s). Approaches for performance improvements and potential monolithic chip implementation are discussed. These studies present the feasibility of a CMOS-based magnetic-shield/heater-free clock with high energy efficiency and sub-ppb stability over a wide range of operation condition.

Atomic-resolution imaging of carbonyl sulfide by laser-induced electron diffraction.

Measurements on the strong-field ionization of carbonyl sulfide molecules by short, intense, 2 µm wavelength laser pulses are presented from experiments where angle-resolved photoelectron distributions were recorded with a high-energy velocity map imaging spectrometer, designed to reach a maximum kinetic energy of 500 eV. The laser-field-free elastic-scattering cross section of carbonyl sulfide was extracted from the measurements and is found in good agreement with previous experiments, performed using conventional electron diffraction. By comparing our measurements to the results of calculations, based on the quantitative rescattering theory, the bond lengths and molecular geometry were extracted from the experimental differential cross sections to a precision better than ±5 pm and in agreement with the known values.

Probing the interplay between geometric and electronic-structure features via high-harmonic spectroscopy.

We present molecular-frame measurements of the recombination dipole matrix element (RDME) in CO2, N2O, and carbonyl sulfide (OCS) molecules using high-harmonic spectroscopy. Both the amplitudes and phases of the RDMEs exhibit clear imprints of a two-center interference minimum, which moves in energy with the molecular alignment angle relative to the laser polarization. We find that whereas the angle dependence of this minimum is consistent with the molecular geometry in CO2 and N2O, it behaves very differently in OCS; in particular, the phase shift which accompanies the two-center minimum changes sign for different alignment angles. Our results suggest that two interfering structural features contribute to the OCS RDME, namely, (i) the geometrical two-center minimum and (ii) a Cooper-like, electronic-structure minimum associated with the sulfur end of the molecule. We compare our results to ab initio calculations using time-dependent density functional theory and present an empirical model that captures both the two-center and the Cooper-like interferences. We also show that the yield from unaligned samples of two-center molecules is, in general, reduced at high photon energies compared to aligned samples, due to the destructive interference between molecules with different alignments.

Strong-field physics in the molecular frame

Laser-aligned carbonyl-sulfide molecules were strong-field ionized using mid-infrared light. Investigating the strong-field effects in the molecular frame allowed to add novel facets to the understanding of the intrinsic nature of strong-field physics.

Femtosecond laser induced Coulomb explosion imaging of aligned OCS oligomers inside helium nanodroplets.

Dimers and trimers of carbonyl sulfide (OCS) molecules embedded in helium nanodroplets are aligned by a linearly polarized 160 ps long moderately intense laser pulse and Coulomb exploded with an intense 40 fs long probe pulse in order to determine their structures. For the dimer, recording of 2D images of OCS+ and S+ ions and covariance analysis of the emission directions of the ions allow us to conclude that the structure is a slipped-parallel shape similar to the structure found for gas phase dimers. For the trimer, the OCS+ ion images and the corresponding covariance maps reveal the presence of a barrel-shaped structure (as in the gas phase) but also other structures not present in the gas phase, most notably a linear chain structure.

Angle dependence of strong-field single and double ionization of carbonyl sulfide

We have studied, experimentally and theoretically, the ionization probability of carbonyl sulfide (OCS) molecules in intense linearly polarized 800-nm laser pulses as a function of the angle between the molecular axis and the laser polarization. Experimentally, the molecules are exposed to two laser pulses with a relative time delay. The first, weaker pulse induces a nuclear rotational wave packet within each molecule such that the ensemble exhibits preferential alignment in the laboratory frame at specific times. The second, stronger pulse induces ionization, and the variation in single and double ionization yields is measured as a function of the delay between the two pulses. The angular dependence of the ionization yield is extracted by fitting the delay-dependent yields to a sum of delay-dependent moments of the rotational wave packet's angular distribution. We compute these same angular-dependent strong-field ionization yields for OCS using time-dependent density-functional theory (TDDFT). For the single-ionization case, our measurements agree well with TDDFT calculations and with previous experiments. Furthermore, analysis of the simulated one-body density reveals that, when averaged over a laser cycle, the resulting hole is delocalized across the molecule for light polarized perpendicular to the molecular axis and mostly localized on the sulfur for parallel polarization. This suggests that preferential molecular alignment is a key parameter for controlling charge migration dynamics initiated by strong-field ionization. For double ionization, the agreement between experiment and theory is less compelling, reflecting the substantial challenges of computing double-ionization yields using TDDFT methods.