ISSN:
1573-7357
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract Superfluid 4 He is unique in having well-defined excitations (R − rotons) with momentum oppositely directed to their velocity. If a beam of R − rotons can be produced, it could be unambiguously detected by quantum evaporation because the atoms will emerge in the opposite quadrant to that for atoms evaporated by R + rotons and phonons. Previous work shows that a heated metal film which is immersed in superfluid 4 He only creates phonons and R + rotons. A sponge-like heater does appear to produce R − rotons but, because it has a long time constant, it cannot be used in time of flight studies. We have developed a source that produces fast pulses of R − rotons suitable for time of flight measurements. The method uses interactions between R + rotons to create R − rotons, so a transient high density of R + rotons in a small confined volume is needed. The source appears to operate as we expect from a model of the evolution of the R + and R − roton populations.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1022582010793
