The HCO⁺-H₂ van der Waals interaction: potential energy and scattering.

We compute the rigid-body, four-dimensional interaction potential between HCO(+) and H2. The ab initio energies are obtained at the coupled-cluster single double triple level of theory, corrected for Basis Set Superposition Errors. The ab initio points are fit onto the spherical basis relevant for quantum scattering.

Ab initio characterization of C(6).

Structural and spectroscopy parameters of C(6) are determined with ab initio calculations confirming the existence of nine isomers. Those geometries with high stability (the linear, where the electronic ground state is a triplet (X(3)Sigma(g)(-)), and the slightly distorted cyclic singlet (X(1)A(1)')) are determined with CASPT2/CASSCF. The effect of the correlation energy on the isomer stability is discussed.

Ab initio characterization of C5.

In this paper, the structure and spectroscopic parameters of the C5 cluster are determined using multiconfigurational quantum chemical methods as implemented in the MOLCAS software. A number of spectroscopic properties (band center positions, l-doubling parameters, and rotational constants) have been characterized. From the new results, the assignments of previous astrophysical observations [J.

Electronic structure calculations on the C4 cluster.

The ground and the electronically excited states of the C4 radical are studied using interaction configuration methods and large basis sets. Apart from the known isomers [l-C4(X(3)Sigmag (-)) and r-C4(X(1)Ag)], it is found that the ground singlet surface has two other stationary points: s-C4(X(1)Ag) and d-C4(X(1)A1). The d-C4 form is the third isomer of this cluster.

3Sigma- -X 3Sigma- electronic transition of linear C6H+ and C8H+ in neon matrixes.

The electronic absorption spectra of linear C6H+ and C8H+ were recorded in 6 K neon matrixes following mass selective deposition. The (1) 3Sigma- -X 3Sigma- electronic transition is identified with the origin band at 515.8 and 628.