International Workshop on Atomic Interactions in Laser Fields - Abstracts
E. Czuchaj
Institute of Theoretical Physics and
Astrophysics, University of Gdansk, Wita Stwosza 57, 80-952 Gdansk,
Poland
e-mail: fizec@univ.gda.pl
The Ca+-H2 and Ca+-N2 species have recently been investigated, among others, in Paul trap experiments, since Ca+ is considered as a candidate for prospective frequency standard applications. The ion storage technique offers also a possibility to study the influence of various neutral gases on the lifetime of ionic levels.
The structures, harmonic frequencies and binding energies for the ground and several excited states of the Ca+-H2 and Ca+-N2 systems are computed at the CASSCF-MRCI (complete active space multireference configuration interaction) level of theory. The valence ab initio calculations are performed in extensive Cartesian Gaussian basis sets for the Ca, H and N atoms. The calculated potential surfaces depend on the coordinate R, the distance between the Ca+ ion and the center-of-mass of the molecule H2 (N2) and on the internuclear separation r of the two H (N) atoms. The calculations are carried out for the C∞v and C2v point groups in a wide range of R and r values and involve all the interaction potentials correlating with the Ca+ levels up to the (4p)2P state. There have been obtained the 2A1, 2B1, 2B2 and 2A2 potential surfaces for the C2v geometry and the 2Σ, 2Π and 2Δ potential surfaces for the collinear configuration. There has also been investigated the dependence of the interaction potentials on the angle γ (between the H2 (N2) axis and the line connecting the Ca+ ion with the center-of-mass of the diatomic) by performing sample calculations in Cs symmetry for some representative points. The calculations have shown that the C∞v geometry is preferential energetically in the collision dynamics for Ca+-N2, whereas the C2v symmetry is absolutely preeminent in the collision process of Ca+-H2. The calculations have revealed the existence of conical intersections between the excited state potential surfaces correlating with the (3d)2D Ca+ term and the (4s)2A1 ground state one, which is of great importance for quenching of the (3d)2D metastable state of the calcium ion. There is also analysed a possibility of stabilization of the Ca+-H2 collision complex leading to the formation of the Ca+-H2 exciplex. Details of the calculations and more results concerning the investigated complexes will be presented during the workshop.
Work supported by the University of Gdansk (Grant No. BW/5400-5-0262-9)