Eur. Phys. J. D (2014) 68: 293
https://doi.org/10.1140/epjd/e2014-50289-9

Regular Article

The A¹Σ_u⁺ system of Mg₂^*

QUEST and Institut für Quantenoptik, Leibniz Universität Hannover, Welfengarten 1, 30167 Hannover, Germany

^a e-mail: knoeckel@iqo.uni-hannover.de

Received: 8 April 2014
Received in final form: 25 June 2014
Published online: 14 October 2014

Abstract

The A¹Σ_u⁺-X¹Σ_g⁺ UV spectrum of Mg₂ has been investigated with high resolution employing Fourier-transform spectroscopy and laser excitation. Computer simulation and fit of line positions to the overlapping structures in the spectra yield precise transition frequencies. Starting with the well characterized ground state X¹Σ_g⁺ from former work, we derived excited energy levels and report on the evaluation of the A¹Σ_u⁺ excited state, which is found to interact with another electronic state, which we identify as the lower part of the (1)¹Π_u state. A coupled channels fit to the level energies of the upper state yields a reliable potential energy curve for the A¹Σ_u⁺ state for the range of vibrational levels 1 ≤ v′ ≤ 46. A potential energy curve for the (1)¹Π_u state is proposed, but the (1)¹Π_u state is only characterized by its coupling to the A state, and no direct transition to a level of the (1)¹Π_u state could be uniquely identified due to the overlapping spectral structures.