Ab Initio Calculations of Alkali-Alkaline Earth Molecules
Johann Potoschnig
Institute of Experimental Physics, Graz University of Technology
http://portal.tugraz.at/portal/page/portal/TU_Graz/Einrichtungen/Institute/Homepages/i5110/forschung/heliumnanodroplets/forschungsgebiet
14:50 - 15:30 Friday 22 May 2015 HS P3 PH02112

In recent years the interest in diatomic molecules consisting of an alkali atom and an alkaline earth atom has been growing due to several proposed applications. Such molecules might be formed in the ultracold temperature regime by the combination of cooled atoms and used in the simulation of quantum systems in optical lattices [1]. Another possible application is the precise measurement of fundamental physical constants [2]. So far mainly homonuclear alkali molecules were investigated in the ultracold temperature regime and more recently heteronuclear alkali molecules. While homonuclear molecules have neither a magnetic nor an electric permanent dipole moment, heteronuclear alkali molecules show a permanent electric dipole moment. If an alkali atom and an alkaline earth atom are combined an additional magnetic moment is obtained due to the unpaired electron. This additional property adds new ways to manipulate the molecule and provides more interactions to model Hamiltonians in optical lattices.
The presented work contains a combined theoretical and experimental investigation of alkali-alkaline earth molecules. The theoretical investigation mainly comprises ab initio calculations with wave function based methods. The main results were obtained with the Molpro quantum chemistry package [3]. The resulting potential energy curves and electronic properties were then used to simulate vibronic spectra, which were then compared to experimental results. The experimental results were obtained by resonance enhanced multi photon ionization time of flight spectroscopy using helium nanodroplets to form the molecules. First the molecule LiCa was investigated as a benchmark because spectroscopic information has been available from gas phase measurements. Then we investigated for the first time the excited states of RbSr and RbCa. Both molecules are promising candidates for the formation of ultracold molecules.

[1] Micheli, A.; Brennen, G. K. & Zoller, P.; A toolbox for lattice-spin models with polar molecules; Nature Physics, 2006, 2, 341-347
[2] Kajita, M.; Gopakumar, G.; Abe, M. & Hada, M.; Characterizing of variation in the proton-to-electron mass ratio via precise measurements of molecular vibrational transition frequencies; Journal of Molecular Spectroscopy, 2014, 300, 99-107
[3] Werner, H.-J.; Knowles, P. J.; Knizia, G.; Manby, F. R.; Schütz, M. & others; MOLPRO, version 2012.1, a package of ab initio programs