Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Ions and the Landau critical velocity in He II.
AU - McClintock, Peter V. E.
N1 - Proceedings of the 128th WE-Heraeus Seminar on Ions and Atoms in Superfluid Helium, Heidelberg Germany, 16-19 May 1994
PY - 1995/9
Y1 - 1995/9
N2 - Investigations of the motion of conventional negative ions (electron bubbles) in He II under pressures above 11 bar have provided the only means of measuring the Landau critical velocity for roton creation, VL, and for studying supercritical dissipation at higher velocities. Earlier work on roton creation is reviewed and it is pointed out that there is still no generally agreed explanation of the fact that the rotons seem to be emitted from the moving ion in pairs; nor is it known why the matrix element characterising the pair emission process should decrease rapidly with pressure. The possibility of studying these phenomena through use either of the "fast ion" (whose nature remains unknown), or of selected ions from the large variety of species that can be injected into He II by the recently developed technique of laser ablation, is discussed.
AB - Investigations of the motion of conventional negative ions (electron bubbles) in He II under pressures above 11 bar have provided the only means of measuring the Landau critical velocity for roton creation, VL, and for studying supercritical dissipation at higher velocities. Earlier work on roton creation is reviewed and it is pointed out that there is still no generally agreed explanation of the fact that the rotons seem to be emitted from the moving ion in pairs; nor is it known why the matrix element characterising the pair emission process should decrease rapidly with pressure. The possibility of studying these phenomena through use either of the "fast ion" (whose nature remains unknown), or of selected ions from the large variety of species that can be injected into He II by the recently developed technique of laser ablation, is discussed.
U2 - 10.1007/BF01338419
DO - 10.1007/BF01338419
M3 - Journal article
VL - 98
SP - 429
EP - 434
JO - Zeitschrift für Physik B Condensed Matter
JF - Zeitschrift für Physik B Condensed Matter
SN - 0722-3277
IS - 3
ER -