Long-range interactions in the ozone molecule: spectroscopic and dynamical points of view

Using the multipolar expansion of the electrostatic energy, we have characterized the asymptotic interactions between an oxygen atom O$(^3P)$ and an oxygen molecule O$_2(^3\Sigma_g^-)$, both in their electronic ground state. We have calculated the interaction energy induced by the permanent electric quadrupoles of O and O$_2$ and the van der Waals energy. On one hand we determined the 27 electronic potential energy surfaces including spin-orbit connected to the O$(^3P)$ + O$_2(^3\Sigma_g^-)$ dissociation limit of the O--O$_2$ complex. On the other hand we computed the potential energy curves characterizing the interaction between O$(^3P)$ and a O$_2(^3\Sigma_g^-)$ molecule in its lowest vibrational level and in a low rotational level. Such curves are found adiabatic to a good approximation, namely they are only weakly coupled to each other. These results represent a first step for modeling the spectroscopy of ozone bound levels close to the dissociation limit, as well as the low energy collisions between O and O$_2$ thus complementing the knowledge relevant for the ozone formation mechanism.Comment: Submitted to J. Chem. Phys. after revisio

Formation of ultracold SrYb molecules in an optical lattice by photoassociation spectroscopy: theoretical prospects

State-of-the-art {\em ab initio} techniques have been applied to compute the potential energy curves for the SrYb molecule in the Born-Oppenheimer approximation for the ground state and first fifteen excited singlet and triplet states within the coupled-cluster framework. The leading long-range coefficients describing the dispersion interactions at large interatomic distances are also reported. The electric transition dipole moments have been obtained as the first residue of the polarization propagator computed with the linear response coupled-cluster method restricted to single and double excitations. Spin-orbit coupling matrix elements have been evaluated using the multireference configuration interaction method restricted to single and double excitations with a large active space. The electronic structure data was employed to investigate the possibility of forming deeply bound ultracold SrYb molecules in an optical lattice in a photoassociation experiment using continuous-wave lasers. Photoassociation near the intercombination line transition of atomic strontium into the vibrational levels of the strongly spin-orbit mixed $b^3\Sigma^+$, $a^3\Pi$, $A^1\Pi$, and $C^1\Pi$ states with subsequent efficient stabilization into the $v^{\prime\prime}=1$ vibrational level of the electronic ground state is proposed. Ground state SrYb molecules can be accumulated by making use of collisional decay from $v^{\prime\prime}=1$ to $v^{\prime\prime}=0$. Alternatively, photoassociation and stabilization to $v^{\prime\prime}=0$ can proceed via stimulated Raman adiabatic passage provided that the trapping frequency of the optical lattice is large enough and phase coherence between the pulses can be maintained over at least tens of microseconds

Two-photon coherent control of femtosecond photoassociation

Photoassociation with short laser pulses has been proposed as a technique to create ultracold ground state molecules. A broad-band excitation seems the natural choice to drive the series of excitation and deexcitation steps required to form a molecule in its vibronic ground state from two scattering atoms. First attempts at femtosecond photoassociation were, however, hampered by the requirement to eliminate the atomic excitation leading to trap depletion. On the other hand, molecular levels very close to the atomic transition are to be excited. The broad bandwidth of a femtosecond laser then appears to be rather an obstacle. To overcome the ostensible conflict of driving a narrow transition by a broad-band laser, we suggest a two-photon photoassociation scheme. In the weak-field regime, a spectral phase pattern can be employed to eliminate the atomic line. When the excitation is carried out by more than one photon, different pathways in the field can be interfered constructively or destructively. In the strong-field regime, a temporal phase can be applied to control dynamic Stark shifts. The atomic transition is suppressed by choosing a phase which keeps the levels out of resonance. We derive analytical solutions for atomic two-photon dark states in both the weak-field and strong-field regime. Two-photon excitation may thus pave the way toward coherent control of photoassociation. Ultimately, the success of such a scheme will depend on the details of the excited electronic states and transition dipole moments. We explore the possibility of two-photon femtosecond photoassociation for alkali and alkaline-earth metal dimers and present a detailed study for the example of calcium

Global potential energy surface for the O2 + N2 interaction. Applications to the collisional, spectroscopic, and thermodynamic properties of the complex

A detailed characterization of the interaction between the most abundant molecules in air is important for the understanding of a variety of phenomena in atmospherical science. A completely {\em ab initio} global potential energy surface (PES) for the O$_2(^3\Sigma^-_g)$ + N$_2(^1\Sigma^+_g)$ interaction is reported for the first time. It has been obtained with the symmetry-adapted perturbation theory utilizing a density functional description of monomers [SAPT(DFT)] extended to treat the interaction involving high-spin open-shell complexes. The computed interaction energies of the complex are in a good agreement with those obtained by using the spin-restricted coupled cluster methodology with singles, doubles and noniterative triple excitations [RCCSD(T)]. A spherical harmonics expansion containing a large number of terms due to the anisotropy of the interaction has been built from the {\em ab initio} data. The radial coefficients of the expansion are matched in the long range with the analytical functions based on the recent {\em ab initio} calculations of the electric properties of the monomers [M. Bartolomei et al., J. Comp. Chem., {\bf 32}, 279 (2011)]. The PES is tested against the second virial coefficient $B(T)$ data and the integral cross sections measured with rotationally hot effusive beams, leading in both cases to a very good agreement. The first bound states of the complex have been computed and relevant spectroscopic features of the interacting complex are reported. A comparison with a previous experimentally derived PES is also provided

Surfaces d'énergie potentielle pour la dynamique : cas de l'interaction C(3P)+OH(X2Pi)

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Time-dependent wave packet and quasiclassical trajectory study of the C(3P)+OH(X 2)CO(X 1+)+H(2S) reaction at the state-to-state level

9 pages, 9 figures, 1 table.The first calculations of state-to-state reaction probabilities and product state-resolved integral cross sections at selected collision energies (0.05, 0.1, 0.5, and 1.0 eV) for the title reaction on the ab initio potential energy surface of [Zanchet et al. J. Phys. Chem. A 110, 12017 (2006)] with the OH reagent in selected rovibrational states (v=0–2, j=0–5) have been carried out by means of the real wave packet (RWP) and quasiclassical trajectory (QCT) methods. State-selected total reaction probabilities have been calculated for total angular momentum J=0 in a broad range of collision energies. Integral cross sections and state-specific rate coefficients have been obtained from the corresponding J=0 RWP reaction probabilities for initially selected rovibrational states by means of a capture model. The calculated RWP and QCT state-selected rate coefficients are practically temperature independent. Both RWP and QCT reaction probabilities, integral cross sections, and rate coefficients are almost independent of the initial rotational excitation. The RWP results are found to be in an overall good agreement with the corresponding QCT results. The present results have been compared with earlier wave packet calculations carried out on the same potential energy surface.Partial financial support from the Spanish Ministry of Education and Science (Project No. CTQ2008-02578/BQU) is gratefully acknowledged. A.Z., P.H., and B.B.-H. acknowledge support from the Institut du Développement des Ressources en Informatique Scientifique (IDRIS) in Orsay (France), the UTINAM laboratory for its fast cluster, and also the Pôle de Sciences Planétaires of Bourgogne Franche-Comté.Peer reviewe