Ve. Sivokon et al., THE STUDY OF PHONON-RIPPLON RESONANCES IN WIGNER CRYSTAL OVER LIQUID-HELIUM, Czechoslovak journal of Physics, 46, 1996, pp. 349-350
The positions and line widths of the phonon-ripplon resonances have be
en measured in Wigner crystal localized over superfluid helium surface
at electron density 1.3 . 10(9) cm(-2) in temperature range 0.08-0.6
K. The positions of the resonances agree with theoretical models avail
able at temperatures not far from melting point. The line width decrea
ses linearly with lowering temperature.