ISSN:
1089-7690
Quelle:
AIP Digital Archive
Thema:
Physik
,
Chemie und Pharmazie
Notizen:
The potential curves, transition energies (Te), and spectroscopic constants (Re, ωe) of several low-lying electronic states of B+2 and selected doubly excited states of B2 are given. The data have been obtained by using a multireference single- and double-excitation (MRD) configuration interaction (CI) approach and a triple-zeta plus polarization AO basis set. The B+2 ground state, which is found here to be X 2Σ+g, shows a rather shallow potential curve (Re =4.015 bohr, ωe =423 cm−1) when compared with that of X 3Σ−g of B2(Re =3.00 bohr, ωe =1051 cm−1, exptl.). The first excited state of B+2, namely 1 2Πu, lies at Te =0.30 eV. Moreover, double excitations relative to X 2Σ+g are essential for the description of a large number of excited states, such as σuσg→π2u(1 4Σ−u, 1 2Σ−u, 1 2Δu, 1 2Σ+u) and σ2u→π2u(1 4Σ−g,1 2Σ−g, 1 2Δg, 1 2Σ+g). Similarly, 2 2Πu arises from the triple excitation σ2uσg→π3u. In the same order as given above, such multiple excitations lead to a significant gain in bond strength (i.e., shorter Re, larger ωe) as a result of the simultaneous depopulation and population of strongly antibonding and bonding MOs, respectively. For neutral B2, similar features are observed for the excitation σ2u→π2u relative to X3Σ−g (leading to 3 1Σ+g) and 1 3Πu (leading to 2 3Πu). As a result of the loss of the two πu electrons, the ground state dissociation energy(De) of B+2(X 2Σ+g), with a calculated value of 1.94 eV, is about 1.12 eV smaller than the experimental De of B2 (X 3Σ−g).
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1063/1.457185
Permalink
