Vibrational Relaxation of DO Induced by Collision with He: A Rigid Bender Close Coupling Study.

The vibrational relaxation of the first excited bending state of DO induced by collision with He is studied at the close coupling level and using the Rigid Bender approximation. A new 4D potential energy surface is calculated and reported for this system. It is then used to determine the low-lying bound states of the DO-He van der Waals complex and to perform scattering calculations.

Scattering resonances in the rotational excitation of HDO by Ne and -H: theory and experiment.

The rotational excitation of a singly deuterated water molecule (HDO) by a heavy atom (Ne) and a light diatomic molecule (H) is investigated theoretically and experimentally in the near-threshold regime. Crossed-molecular-beam measurements with a variable crossing angle are compared to close-coupling calculations based on high-accuracy potential energy surfaces. The two lowest rotational transitions, 0 → 1 and 0 → 1, are probed in detail and a good agreement between theory and experiment is observed for both transitions in the case of HDO + Ne, where scattering resonances are however blurred out experimentally.

Quantum study of the rovibrational relaxation of HF by collision with He on a new potential energy surface.

The HF molecule is considered the main reservoir of fluorine in the interstellar medium (ISM). Also, the interactions of this molecule with the most common atoms and molecules in the ISM have attracted great interest from the astrochemical community. Collisions between HF and helium have recently caused controversy following a study using a two-dimensional SAPT potential energy surface (PES) that exhibited large discrepancies with previous scattering calculations based on more recent potentials.

A Rigid Bender Study of the Bending Relaxation of HO and DO by Collisions with Ar.

The bending relaxation of HO and DO by collisions with Ar is studied at the Close Coupling level. Two new 4D PES are developed for these two systems. They are tested by performing rigid rotor calculations as well as by computing the DO-Ar bound states.

A Comparative Study of the Cold Collisions of HO and DO with Ne.

The present work is dedicated to the first theoretical study of the rotationally inelastic collisions of Ne with HO and its isotopologue DO in an attempt to analyze the effect on the dynamics of H substitution by deuterium. To this aim two new potential energy surfaces are developed. Their quality is tested by computing the bound states of the complexes and comparing them with those most recently reported by other teams.

Hyperthermal Dynamics and Kinetics of the C(P) + N(X) → CN(X) + N(S) Reaction.

The hyperthermal dynamics and kinetics of the title reaction, which plays an important role in hypersonic chemistry for atmospheric entry vehicles, are investigated using quasi-classical trajectory methods on a recently developed ground electronic state potential energy surface. The dynamics calculations indicated that the reaction follows a complex-forming mechanism, despite its large endoergicity. The calculated differential cross section is forward-backward symmetric, consistent with a long-lived reaction intermediate supported by the NCN potential well.

An explicitly correlated six-dimensional potential energy surface for the SiCSi + H complex.

The first six-dimensional potential energy surface (PES) for the SiCSi + H complex is presented in this work. This surface is developed from a large number of energies computed at the explicitly correlated coupled-cluster level of theory together with the augmented correlation-consistent polarized valence triple zeta basis set (CCSD(T)-F12/aug-cc-pVTZ). These energies are fitted to an analytical function through a procedure that combines spline, least-squares, and kernel-based methods.

Study of the CN(XΣ) + N(S) Reaction at High Temperatures: Potential Energy Surface and Thermal Rate Coefficients.

Reactions involving C and N play an essential role in the chemistry around the surface of a hypersonic spacecraft during its atmospheric re-entry. The collision of CN with other molecules and atoms has particular interest in aerothermodynamic modeling. This work focuses on the study of the CN + N → N + C reaction in the triplet manifold A″ of CN.

A close coupling study of the bending relaxation of HO by collision with He.

We present a close coupling study of the bending relaxation of HO by collision with He, taking explicitly into account the bending-rotation coupling within the rigid-bender close-coupling method. A 4D potential energy surface is developed based on a large grid of ab initio points calculated at the coupled-cluster single double triple level of theory. The bound states energies of the He-HO complex are computed and found to be in excellent agreement with previous theoretical calculations.

Rotational Transitions of HOC Induced by Collision with He at Low Temperatures.

The HOC molecule has for long been detected in several regions of the interstellar medium (ISM). The collisional ro-vibrational rate coefficients of this molecule with the most common colliders in the ISM are then required for applying nonlocal thermal equilibrium models. However, this molecule has a low bending frequency (249 cm), and the use of the rigid rotor approximation is therefore limited to low collision energies.

Rigid-Bender Close-Coupling Treatment of the Inelastic Collisions of HO with -H.

We present a new method taking explicitly into account the coupling between rotation and bending of a nonlinear triatomic molecule colliding with an atom. This approach based on a rigid-bender treatment of the triatomic molecule was originally developed for the case of triatomic molecule linear at equilibrium. It is here extended to the case of a colliding bent triatomic molecule at equilibrium and applied to the case of the -H + HO inelastic collision using a new HO--H adiabatically reduced 4D potential.

A benchmark for the size of the QM system required for accurate hybrid QM/MM calculations on the metal site of the protein copper, zinc superoxide dismutase.

The protein superoxide dismutase 1 (SOD1) is a copper and zinc-binding protein that has been implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS). The Zn(II) binding to SOD1 is critical for the stability of the protein, and has been by itself implicated in ALS pathogenesis. Hence, the quantum mechanical (QM) study of the Zn(II)-site of SOD1 is relevant for understanding ALS.

Quantum and quasiclassical trajectory studies of rotational relaxation in Ar-N collisions.

The collision of N with Ar is studied using quantum and classical methods. The dynamics was followed on a new potential energy surface based on ab initio energies computed at the UCCSD(T)-F12a/aug-cc-pVTZ level, using the correct analytical long range behaviour and a reproducing kernel representation. Comparison with multi-reference MRCI+Q calculations establish that UCCSD(T)-F12a is a sufficiently high level of theory for this problem.

Communication: Vibrational relaxation of CO(Σ) in collision with Ar(S) at temperatures relevant to the hypersonic flight regime.

Vibrational energy relaxation (VER) of diatomics following collisions with the surrounding medium is an important elementary process for modeling high-temperature gas flow. VER is characterized by two parameters: the vibrational relaxation time τ and the state relaxation rates. Here the vibrational relaxation of CO(ν=0←ν=1) in Ar is considered for validating a computational approach to determine the vibrational relaxation time parameter (pτ) using an accurate, fully dimensional potential energy surface.

Reactive collisions for NO(Π) + N(S) at temperatures relevant to the hypersonic flight regime.

The NO(XΠ) + N(S) reaction which occurs entirely in the triplet manifold of NO is investigated using quasiclassical trajectories and quantum simulations. Fully-dimensional potential energy surfaces for the A' and A'' states are computed at the MRCI+Q level of theory and are represented using a reproducing kernel Hilbert space. The N-exchange and N-formation channels are followed by using the multi-state adiabatic reactive molecular dynamics method.

Heavy metal levels in dune sands from Matanzas urban resorts and Varadero beach (Cuba): Assessment of contamination and ecological risks.

Concentrations of chromium (Cr), nickel (Ni), copper (Cu), zinc (Zn) and lead (Pb) in dune sands from six urban and suburban Matanzas (Cuba) resorts and Varadero beach were estimated by X-ray fluorescence analysis. Ranges of metal contents in dune sands show a strong variation across the studied locations (in mg/kg(-1)): 20-2964 for Cr, 17-183 for Ni, 17-51 for Cu, 18-88 for Zn and 5-29 for Pb. The values of contamination factors and contamination degrees how that two of the studied Matanzas's resorts (Judio and Chirry) are strongly polluted.

Rotational excitation of HCN by para- and ortho-H₂.

Rotational excitation of the hydrogen cyanide (HCN) molecule by collisions with para-H2(j = 0, 2) and ortho-H2(j = 1) is investigated at low temperatures using a quantum time independent approach. Both molecules are treated as rigid rotors. The scattering calculations are based on a highly correlated ab initio 4-dimensional (4D) potential energy surface recently published.

Rovibrational energy transfer in the He-C3 collision: potential energy surface and bound states.

We present a four-dimensional potential energy surface (PES) for the collision of C3 with He. Ab initio calculations were carried out at the coupled-cluster level with single and double excitations and a perturbative treatment of triple excitations, using a quadruple-zeta basis set and mid-bond functions. The global minimum of the potential energy is found to be -26.

A new ab initio potential energy surface for the collisional excitation of HCN by para- and ortho-H2.

We present a new four-dimensional potential energy surface for the collisional excitation of HCN by H2. Ab initio calculations of the HCN-H2 van der Waals complex, considering both molecules as rigid rotors, were carried out at the explicitly correlated coupled cluster with single, double, and perturbative triple excitations [CCSD(T)-F12a] level of theory using an augmented correlation-consistent triple zeta (aVTZ) basis set. The equilibrium structure is linear HCN-H2 with the nitrogen pointing towards H2 at an intermolecular separation of 7.

Ro-vibrational relaxation of HCN in collisions with He: rigid bender treatment of the bending-rotation interaction.

We present a new theoretical method to treat atom-rigid bender inelastic collisions at the Close Coupling (RB-CC) level in the space fixed frame. The coupling between rotation and bending is treated exactly within the rigid bender approximation and we obtain the cross section for the rotational transition between levels belonging to different bending levels. The results of this approach are compared with those obtained when using the rigid bender averaged approximation (RBAA) introduced in our previous work dedicated to this system.

The interaction of He with vibrating HCN: potential energy surface, bound states, and rotationally inelastic cross sections.

A four-dimensional potential energy surface representing the interaction between He and hydrogen cyanide (HCN) subjected to bending vibrational motion is presented. Ab initio calculations were carried out at the coupled-cluster level with single and double excitations and a perturbative treatment of triple excitations, using a quadruple-zeta basis set and mid-bond functions. The global minimum is found in the linear He-HCN configuration with the H atom pointing towards helium at the intermolecular separation of 7.

Potential energy surface and rovibrational energy levels of the H2-CS van der Waals complex.

Owing to its large dipole, astrophysicists use carbon monosulfide (CS) as a tracer of molecular gas in the interstellar medium, often in regions where H(2) is the most abundant collider. Predictions of the rovibrational energy levels of the weakly bound complex CS-H(2) (not yet observed) and also of rate coefficients for rotational transitions of CS in collision with H(2) should help to interpret the observed spectra. This paper deals with the first goal, i.

A new ab initio potential energy surface for the collisional excitation of O2 by H2.

We present a new four dimensional (4D) potential energy surface for the O(2)-H(2) system. Both molecules were treated as rigid rotors. Potential was obtained from the electronic structure calculations using a partially spin-restricted coupled cluster with the single, double and perturbative triple excitations [RCCSD(T)] method.