EGAS41 - Swansea University

41 st EGAS CP 148 Gdańsk 2009
Relativistic Jahn-Teller effects in the quartet states of K 3 and
Rb 3 : Experimental and theoretical investigations
G. Auböck 1 , A.W. Hauser 1 , C. Callegari 1 , W.E. Ernst 1,∗
1 Institute of Experimental Physics, Graz University of Technology, Petersgasse 16,
A-8010 Graz, Austria
∗ Corresponding author: wolfgang.ernst@tugraz.at,
Spectroscopy of alkali-metal complexes on helium droplets (He N , N = 1000 - 10000)
provides the unique opportunity to observe high-spin species which exhibit prominent
spin-orbit (SO) effects. In this work we present laser-induced-fluorescence and magneticcircular-dichroism
(MCD) spectra of the 2 4 E ′ - 1 4 A ′ 2 band of Rb 3 and K 3 on He N .
For Rb 3 we find a progression of four SO split bands, weakly perturbed by linear vibronic
(Jahn-Teller) coupling. The K 3 transition was previously observed, and interpreted
in terms of a linear and quadratic Jahn-Teller effect in the 2 4 E ′ state [1]. The structure
of the MCD spectrum, however, clearly reveals the importance of SO coupling also for
the K 3 transition, and suggests a different assignment with weak linear- and no significant
quadratic JT coupling [2]. The observed strong C-type MCD spectra arise from different
populations of the ground-state Zeeman sublevels. Thus a quantitative analysis allows
a determination of the spin temperature and since alkali metal complexes are situated
on the surface of the helium droplet, this corresponds to a determination of the surface
temperature. Our results from the trimer spectra are consistent with the value of 0.4K
which is found in the interior of a droplet.
In our theoretical calculations, we apply the Multireference Rayleigh Schrödinger Perturbation
Theory of second order to obtain the adiabatic potential energy surfaces of the
1 4 A ′ 2 electronic ground state and the 24 E ′ excited state of K 3 and Rb 3 . As stated above,
both trimers show a typical E×e Jahn-Teller distortion in their 2 4 E ′ state, which is analyzed
in terms of the relativistic Jahn-Teller effect theory. Linear, quadratic as well as
spin-orbit coupling terms are extracted from the ab initio results and used to obtain theoretical
spectra for a direct comparison with the laser-induced fluorescence and magnetic
circular dichroism spectra.
References
[1] J. Reho et al., J. Chem. Phys. 115, 10265 (2001)
[2] G. Auböck et al., J. Chem. Phys. 129, 114501 (2008)
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