193 research outputs found
Alkali Atoms Attached to He Nanodroplets
We have experimentally studied the electronic excitation of Na
atoms attached to He droplets by means of laser-induced fluorescence as
well as beam depletion spectroscopy. From the similarities of the spectra
(width/shift of absorption lines) with these of Na on He droplets, we
conclude that sodium atoms reside in a ``dimple'' on the droplet surface and
that superfluid-related effects are negligible. The experimental results are
supported by Density Functional calculations at zero temperature, which confirm
the surface location of Na, K and Rb atoms on He droplets. In the case of
Na, the calculated shift of the excitation spectra for the two isotopes is in
good agreement with the experimental data.Comment: 6 pages, 3 figures, sent to JLT
Kilohertz laser ablation for doping helium nanodroplets
A new setup for doping helium nanodroplets by means of laser ablation at
kilohertz repetition rate is presented. The doping process is characterized and
two distinct regimes of laser ablation are identified. The setup is shown to be
efficient and stable enough to be used for spectroscopy, as demonstrated on
beam-depletion spectra of lithium atoms attached to helium nanodroplets. For
the first time, helium droplets are doped with high temperature refractory
materials such as titanium and tantalum. Doping with the non-volatile DNA basis
Guanine is found to be efficient and a number of oligomers are detected
Spectroscopy of PTCDA attached to rare gas samples: clusters vs. bulk matrices. I. Absorption spectroscopy
The interaction between PTCDA (3,4,9,10-perylene-tetracarboxylic-dianhydride)
and rare gas or para-hydrogen samples is studied by means of laser-induced
fluorescence excitation spectroscopy. The comparison between spectra of PTCDA
embedded in a neon matrix and spectra attached to large neon clusters shows
that these large organic molecules reside on the surface of the clusters when
doped by the pick-up technique. PTCDA molecules can adopt different
conformations when attached to argon, neon and para-hydrogen clusters which
implies that the surface of such clusters has a well-defined structure and has
not liquid or fluxional properties. Moreover, a precise analysis of the doping
process of these clusters reveals that the mobility of large molecules on the
cluster surface is quenched, preventing agglomeration and complex formation
High-resolution spectroscopy of triplet states of Rb2 by femtosecond pump-probe photoionization of doped helium nanodroplets
The dynamics of vibrational wave packets in triplet states of rubidium dimers
(Rb2) formed on helium nanodroplets are studied using femtosecond pump-probe
photoionization spectroscopy. Due to fast desorption of the excited Rb2
molecules off the droplets and due to their low internal temperature, wave
packet oscillations can be followed up to very long pump-probe delay times
>1.5ns. In the first excited triplet state (1)^3\Sigma_g^+, full and fractional
revivals are observed with high contrast. Fourier analysis provides
high-resolution vibrational spectra which are in excellent agreement with ab
initio calculations
Surface location of sodium atoms attached to He-3 nanodroplets
We have experimentally studied the electronic excitation of
Na atoms attached to He droplets by means of laser-induced fluorescence as
well as beam depletion spectroscopy. From the similarities of the spectra
(width/shift of absorption lines) with these of Na on He droplets, we
conclude that sodium atoms reside in a ``dimple'' on the droplet surface. The
experimental results are supported by Density Functional calculations at zero
temperature, which confirm the surface location of sodium on He droplets,
and provide a microscopic description of the ``dimple'' structure.Comment: 4 pages, 5 figure
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