3,497 research outputs found
Dielectric molding apparatus Patent
Dielectric apparatus for heating, fusing, and hardening of organic matrix to form plastic material into shaped produc
Coherent, multi-heterodyne spectroscopy using stabilized optical frequency combs
The broadband, coherent nature of narrow-linewidth fiber frequency combs is
exploited to measure the full complex spectrum of a molecular gas through
multi-heterodyne spectroscopy. We measure the absorption and phase shift
experienced by each of 155,000 individual frequency comb lines, spaced by 100
MHz and spanning from 1495 nm to 1620 nm, after passing through a hydrogen
cyanide gas. The measured phase spectrum agrees with Kramers-Kronig
transformation of the absorption spectrum. This technique can provide a full
complex spectrum rapidly, over wide bandwidths, and with hertz-level accuracy.Comment: 4 pages, 3 figure
Vibrational Feshbach Resonances Mediated by Nondipole Positron-Molecule Interactions
Measurements of energy-resolved positron-molecule annihilation show the
existence of positron binding and vibrational Feshbach resonances. The existing
theory describes this phenomenon successfully for the case of infrared-active
vibrational modes which allow dipole coupling between the incident positron and
the vibrational motion. Presented here are measurements of positron-molecule
annihilation made using a recently developed cryogenic positron beam capable of
significantly improved energy resolution. The results provide evidence of
resonances associated with infrared-inactive vibrational modes, indicating that
positron-molecule bound states may be populated by nondipole interactions. The
anticipated ingredients for a theoretical description of such interactions are
discussed.Comment: 5 pages, 2 figures, Phys. Rev. Lett. (in press
Proton-Induced X-Ray Emission Spectrometry in Archaeology
Proton-induced x-ray emission (PIXE) spectrometry is fast developing a reputation as a powerful analytical tool in the study of a range of ancient materials, including bronze, iron, gold, glass, faience, and smelting slag. PIXE data allows determination of the primary constituents which would indicate their recipe of production and determine their bulk physical properties (e.g., color of a glass, brittleness in a metal), and of a wide range of trace elements which may indicate the source of raw material s from which an artifact was constituted. Over the past seven years, PIXE spectrometry\u27s primary advantage over other recognized methods now being applied in archaeological research (particularly, xrf spectrometry and SEM/EDAX) - -that protons induce very little bremsstrahlung and therefore contribute very little to spectrum background during analysis has been much enhanced through the use of various kinds of selective filters in the detection system that heavily suppress the x-ray signal of dominant element(s) in the artifact\u27s matrix (Cu in bronze, Si and Ca in glass, etc.). PIXE detection limits are kept exceptionally low (usually in the 10 ppm to 100 ppm range), because the selective filters almost entirely eliminate secondary background effects arising from response inertia in the detection system\u27s electronics. Archaeological applications of the PIXE method, as reviewed here, now cover both the Old World, the New World, ancient Asia and Polynesia, and a time-span of the 5th millennium B.C. through to the 19th century A.D
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