The A 2Π u state of [formula omitted]: Electric properties, fine and hyperfine coupling constants, and magnetic moments ( g-factors). A theoretical study

Abstract

Several properties are calculated for A 2Π u of N 2 + —the majority for the first time—including electric and magnetic moments, and fine/hyperfine structure (fs/hfs) parameters. The new results are compared with our previous ones for X 2 Σ g + and B 2 Σ u + of N 2 + [P.J. Bruna, F. Grein, J. Mol. Spectrosc. 227 (2004) 67–80]. The electric quadrupole Θ and hexadecapole Φ moments, polarizability α, and hfs constants a, b, c, d, eQq 0, eQq 2 are evaluated at the density functional theory (DFT) level [B3LYP/aug-cc-pVQZ]. The fs constants (spin–orbit coupling A Π, Λ-doubling p, q, spin-rotation γ Π), and magnetic moments ( g-factors) are obtained via 2nd-order sum-over-states expansions, using wavefunctions and matrix elements obtained with a multireference configuration interaction (MRDCI) method, and the Breit–Pauli Hamiltonian. At equilibrium, 2nd-order properties of A 2Π u are dominated by its coupling with B 2 Σ u + . For the A state, two independent components are reported for traceless tensor properties (multipoles Θ and Φ; hfs parameters c/d and q 0/ q 2) and three for traced properties (polarizability α and g-factors), i.e., one more component than for axially symmetric Σ states. The currently available experimental data on A 2 Π u ( N 2 + ) — limited to A Π, p, and q—are well reproduced by our theoretical results.