engleski

Predictions for RbCs bands observation on helium clusters

RbCs is the heaviest heteronuclear alkali molecule which is of considerable interest for several applications. It is marked by large spin-orbit interaction stemming from both rubidium and cesium atoms. It also has appreciable permanent electric dipole moment and thus could be used in novel methods of molecular cooling. In addition to all these interesting facts, it can be formed on the surface of the nano-size helium cluster, which as a cryostat helps in forcing the molecule into the lowest vibrational state of lowest triplet or singlet electronic states. It is in principle possible to predict some of the RbCs absorption bands that can be detected in future laser excitation experiments. Laser induced fluorescence from cold RbCs can be also discussed. However, necessary transition dipole moments are not known and additional spectroscopic measurements are needed. We carried out a series of absorption measurements in very dense vapor of Rb-Cs mixture. At temperatures around 650 K we clearly observed a new band peaking at about 563 nm. Since it appeared as a single peak we deduced its triplet origin. However, at slightly higher temperatures (~700 K) another diffuse band extending from 570 till 600 nm appeared, also most probably from RbCs molecules. Resonance lines of Rb and Cs did not reveal any satellite bands as it is well known in homonuclear molecules. Theoretical treatment is very complex, but we hope that absorption measurements at high densities will help in deciding about most prominent transitions in RbCs molecule. We also plan laser induced fluorescence experiments, which will contribute to the knowledge about the structure of heteronuclear alkali molecules. This knowledge could be then applied to spectroscopy of RbCs on the helium clusters.

helium; nanodroplets; absorption; cesium; rubidium

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