18,872 research outputs found
Monolayers of 3He on the Surface of Bulk Superfluid 4He
We have used quantum evaporation to investigate the two-dimensional fermion
system that forms at the free surface of (initially isotopically pure) 4He when
small quantities of 3He are added to it. By measuring the first-arrival times
of the evaporated atoms, we have determined that the 3He-3He potential in this
system is V_3S/k_B=(0.23+/-0.02) K nm^2 (repulsive) and estimated a value of
m_3S=(1.53+/-0.02)m_3 for the zero-coverage effective mass. We have also
observed the predicted second layer-state which becomes occupied once the first
layer-state density exceeds about 0.6 monolayers.Comment: 2 pages, 3 figures. Submitted to Proc. LT-22 (1999) to appear in
Physica
Relative Evaporation Probabilities of 3He and 4He from the Surface of Superfluid 4He
We report a preliminary experiment which demonstrates that 3He atoms in
Andreev states are evaporated by high-energy (E/k_B ~ 10.2 K) phonons in a
quantum evaporation process similar to that which occurs in pure 4He. Under
conditions of low 3He coverage, high-energy phonons appear to evaporate 3He and
4He atoms with equal probability. However, we have not managed to detect any
3He atoms that have been evaporated by rotons, and conclude that the
probability of a roton evaporating a 3He atom is less than 2% of the
probability that it evaporates a 4He atom.Comment: 2 pages, 3 figures. Submitted to Proc. LT-22 (1999) Physica
Workshop on Moon in Transition: Apollo 14, KREEP, and Evolved Lunar Rocks
Lunar rocks provide material for analyzing lunar history and now new evaluation procedures are available for discovering new information from the Fra Mauro highlands rocks, which are different from any other lunar samples. These and other topics were discussed at this workshop, including a new evaluation of the nature and history of KREEP, granite, and other evolved lunar rock types, and ultimately a fresh evaluation of the transition of the moon from its early anorthosite-forming period to its later stages of KREEPy, granitic, and mare magmatism. The summary of presentations and discussion is based on notes taken by the respective summarizers during the workshop
Observation and Modeling of Coronal "Moss" With the EUV Imaging Spectrometer on Hinode
Observations of transition region emission in solar active regions represent
a powerful tool for determining the properties of hot coronal loops. In this
Letter we present the analysis of new observations of active region moss taken
with the Extreme Ultraviolet Imaging Spectrometer (EIS) on the \textit{Hinode}
mission. We find that the intensities predicted by steady, uniformly heated
loop models are too intense relative to the observations, consistent with
previous work. To bring the model into agreement with the observations a
filling factor of about 16% is required. Furthermore, our analysis indicates
that the filling factor in the moss is nonuniform and varies inversely with the
loop pressure
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