Using the quantum chemistry package MOLPRO and an adapted basis set, we have calculated the adiabatic potential energy curves of the first 20 1 + , 19 3 + , 12 1 , 9 3 , 4 1 and 2 3 electronic states of the HeH + molecular ion in CASSCF and CI approaches. The results are compared with previous works. The radial and rotational non-adiabatic coupling matrix elements as well as the dipole moments are also calculated. The asymptotic behaviour of the potential energy curves and of the various couplings between the states is also studied. Using the radial couplings, the diabatic representation is defined and we present an example of our diabatization procedure on the 1 + states.

The total and partial photodissociation cross sections of the molecular ion HeH + are computed by timedependent methods for fragmentation into the excited shells n =1,2,3 up to a photon energy of 40 eV. 1 ⌺ + and 1 ⌸ states are considered for parallel and perpendicular transitions for different initial rotational or vibrational excitations. Nonadiabatic radial and rotational couplings are taken into account. The results from coupledchannel equations are compared with the Born-Oppenheimer approximation. A time-dependent calculation with a femtosecond laser pulse is carried out to simulate a recent crossed beam photodissociation imaging experiment with vacuum ultraviolet free-electron laser ͓H. B. Pedersen et al., Phys. Rev. Lett. 98, 223202 ͑2007͔͒. The dominance of photodissociation perpendicular to the photon polarization is confirmed.

Relaxation of energetic S(1D) atoms in Xe gas: Comparison of ab initio calculations with experimental data J. Chem. Phys. 135, 024304 (2011) Ultracold O2 + O2 collisions in a magnetic field: On the role of the potential energy surface J. Chem. Phys. 134, 124310 (2011) Cold and ultracold NH-NH collisions: The field-free case J. Chem. Phys. 134, 124309 (2011) Quantum and classical study of surface characterization by three-dimensional helium atom scattering J. Chem. Phys A quantal study of the rotational excitation of nitrogen molecules by sodium atoms is carried out. We present the two-dimensional potential energy surface of the NaN 2 complex, with the N 2 molecule treated as a rigid rotor. The interaction potential is computed using the spin unrestricted coupledcluster method with single, double, and perturbative triple excitations (UCCSD(T)). The long-range part of the potential is constructed from the dynamic electric dipole polarizabilities of Na and N 2 . The total, differential, and momentum transfer cross sections for rotationally elastic and inelastic transitions are calculated using the close-coupling approach for energies between 5 cm −1 and 1500 cm −1 . The collisional and momentum transfer rate coefficients are calculated for temperatures between 100 K and 300 K, corresponding to the conditions under which Na-N 2 collisions occur in the mesosphere.

Rotational product-pair correlations have been observed, while ND3 was rotationally excited, D2 was simultaneously rotationally excited and de-excited.

Interaction of the NO 3pπ Rydberg state with Ar: Potential energy surfaces and spectroscopy J. Chem. Phys. 138, 214313 (2013) A new, four-dimensional potential energy surface for the interaction of NH 3 and ND 3 with Ar is computed using the coupled-cluster method with single, double, and perturbative triple excitations and large basis sets. The umbrella motion of the ammonia molecule is explicitly taken into account. The bound states of both NH 3 -Ar and ND 3 -Ar are calculated on this potential for total angular momentum values from J = 0 to 10, with the inclusion of Coriolis interactions. The energies and splittings of the rovibrational levels are in excellent agreement with the extensive high-resolution spectroscopic data accumulated over the years in the infrared and microwave regions for both complexes, which demonstrates the quality of the potential energy surface. © 2014 AIP Publishing LLC.