SPECTRA OF ALKALI DIMERS ADSORBED ON THE HELIUM NANO CRIOSTAT
Cold nanodroplets (or clusters) of about 104 helium atoms have been shown to provide a weakly interacting, low temperature environment of 0.37 K (nano cryostat) for the formation and spectroscopy of molecules. Alkali metal atoms picked up by a beam of helium nanodroplets, remain on the helium surface where they „skate“ around and form molecules in cold collisions. After the formation of molecules with a certain large binding energy, this energy is released into the surrounding helium cluster and causes evaporation of helium atoms, one helium atom for every 5 cm-1 of energy. As a result, helium droplets loaded with weakly bound molecules are observed at larger abundance downstream in the helium cluster beam than droplets loaded with strongly bound molecules.
Due to the low temperature of the helium environment, only the lowest vibrational state is populated in each case. This enables easy quantum simulation of absorption spectra if the relevant potential curves are available. Few additional approximations lead to analytical formulas [1,2] which are suitable for the analysis of the experimental spectra. Our spectral simulations were performed by using the set of potential curves calculated in Hund’s case (a). The direct comparison with experimental observation was made for Cs2 molecule . Recently, this method was applied for heteronuclear alkali molecules KRb  and RbCs  stabilized on the cold helium droplet. The results will be shown and discussed.
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