Volume 88, Number 2, October 2009
Article Number 26007
Number of page(s) 6
Section Condensed Matter: Structural, Mechanical and Thermal Properties
Published online 10 November 2009
EPL, 88 (2009) 26007
DOI: 10.1209/0295-5075/88/26007

Anomalously sharp phonon excitations in 3He droplets

N. Poertner, J. P. Toennies, A. F. Vilesov, G. Benedek and V. Hizhnyakov

Max-Planck-Institut für Dynamik und Selbstorganisation - Bunsenstraße 10, D-37077 Göttingen, Germany, EU

received 20 July 2009; accepted in final form 9 October 2009; published October 2009
published online 10 November 2009

The absorption spectra of the S1 $\leftarrow$ S0 electronic transition of a glyoxal molecule (C2H2O2) embedded inside a pure Fermionic 3He droplet shows a sharp zero-phonon excitation line followed by a slowly decreasing wing extending to higher frequencies. Superimposed upon the wing, a small but sharp peak is observed at $\Delta E$ = 0.99 meV. The wing is shown to be due to the continuum of particle-hole pair excitations while the sharp peak results from the excitation of localized phonons of the snowball shell of 3He atoms surrounding the chromophore molecule. The exceptional sharpness of the observed phonon peak (at least 10 times narrower than the ordinary bulk phonon peak at the same energy) is attributed to the localization associated with Friedel-like oscillations of the 3 He liquid density.

67.30.em - Exitations.
67.30.ej - Films and restricted geometries.

© EPLA 2009