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 [3].
Recently, this method was applied for heteronuclear alkali molecules KRb [4]
and RbCs [5] stabilized on the cold helium droplet. The results will be shown
and discussed.
1. Gislason E A 1973 J. Chem. Phys. 58 3702
2. Hüpper B and Eckhardt B 1998 Phys. Rev. A 57 1536
3. Ernst W E, Huber R, Jiang S, Beuc R, Movre M and Pichler G 2006 J. Chem. Phys. 124 024313
4.
Beuc R, Movre M, Ban T, Pichler G, Aymar M, Dulieu O
and Ernst W E,
J. Phys. B, to be published
5. Beuc R, Movre M, Vdovic S, Pichler G, Nevsesyan A, Varzhapetyan T and Sarkisyan D, J. Phys. B, in preparation