Hamburg 2009 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
MO: Fachverband Molekülphysik
MO 14: Cluster
MO 14.7: Vortrag
Mittwoch, 4. März 2009, 15:45–16:00, VMP 6 HS-F
Spectroscopy of PTCDA molecules attached to large hydrogen clusters — •Oliver Bünermann, Matthieu Dvorak, and Frank Stienkemeier — Physikalisches Institut, Universität Freiburg, Hermann-Herder-Str. 3, 79104 Freiburg
Up to now, the two helium isotopes 3He, 4He are the only observed bulk superfluids. However, theoretical calculations have predicted a superfluid phase also for molecular hydrogen under certain conditions[1]. The calculated transition temperature has been calculated to lie well below the tripelpoint for solidification. Experimentalists have attempted to supercool hydrogen by different means, but so far, the phase transition has not been observed. An alternative method to supercool a gas is given by a supersonic expansion into vacuum. In our laboratory we followed this approach and formed a beam of large para-hydrogen clusters in this way. To check the state of aggregation we doped the clusters with an organic molecule and probed its electronic spectrum with laser induced fluorescence (LIF) techniques. The width and shift as well as the line shape of transitions give us information about the interaction of the molecule with the hydrogen clusters. We will present LIF spectra of PTCDA attached to hydrogen, argon and helium clusters. The measurements suggest that hydrogen clusters are solid. However, a comparison with similar measurements performed by Momose et al. [2] show peculiar differences.
[1] Maris et al., J.LowTemp.Phys 51, 471 (1983)
[2] Kuma et al., J.Chem.Phy. 127, 214301 (2007)