95 research outputs found
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 and
an oxygen molecule O, both in their electronic ground state.
We have calculated the interaction energy induced by the permanent electric
quadrupoles of O and O and the van der Waals energy. On one hand we
determined the 27 electronic potential energy surfaces including spin-orbit
connected to the O + O dissociation limit of the
O--O complex. On the other hand we computed the potential energy curves
characterizing the interaction between O and a O
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 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 , , , and states with
subsequent efficient stabilization into the vibrational
level of the electronic ground state is proposed. Ground state SrYb molecules
can be accumulated by making use of collisional decay from
to . Alternatively, photoassociation and stabilization to
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 + N 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 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'Ă©nergie potentielle pour la dynamique : cas de l'interaction C(3P)+OH(X2Pi)
International audienc
Theoretical dynamical study of radical-radical reactions of atmospheric and astrophysical interest: OH+atom
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=0â2, j=0â5) 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 DĂ©veloppement des Ressources en
Informatique Scientifique (IDRIS) in Orsay (France), the
UTINAM laboratory for its fast cluster, and also the PĂŽle de
Sciences Planétaires of Bourgogne Franche-Comté.Peer reviewe
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