Results 1 - 10 of 20664
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[en] The wave nature of particles is rarely observed, in part because of their very short de Broglie wavelengths in most situations. However, even with wavelengths close to the size of their surroundings, the particles couple to their environment (for example, by gravity, Coulomb interaction, or thermal radiation). These couplings shift the wave phases, often in an uncontrolled way, and the resulting decoherence, or loss of phase integrity, is thought to be a main cause of the transition from quantum to classical behavior. How much interaction is needed to induce this transition? Here we show that a photoelectron and two protons form a minimum particle/slit system and that a single additional electron constitutes a minimum environment. Interference fringes observed in the angular distribution of a single electron are lost through its Coulomb interaction with a second electron, though the correlated momenta of the entangled electron pair continue to exhibit quantum interference
[en] We report on the first results of a search for optical-wavelength photons mixing with hypothetical hidden-sector paraphotons in the mass range between 10-5 and 10-2 electron volts for a mixing parameter greater than 10-7. This was a generation-regeneration experiment using the ''light shining through a wall'' technique in which regenerated photons are searched for downstream of an optical barrier that separates it from an upstream generation region. The new limits presented here are approximately three times more sensitive to this mixing than the best previous measurement. The present results indicate no evidence for photon-paraphoton mixing for the range of parameters investigated.
[en] We demonstrate simultaneous dual-wavelength operation in the coupled-cavity dye laser with self-seeding technique. The laser cavity can be decomposed with two grazing-incidence cavities and a standing wave cavity. The output beams are independently tunable and collinear. Operational characteristic have been investigated by changing the cavity length, incident angle, and the like. We also discuss the regenerative amplification of self-seeded dye laser.
[en] The diameter of Betelgeuse (α Orionis) has been measured at a wavelength of 11.15 μm using the Infrared Spatial Interferometer over the past 15 years. During this 1993-2009 time period the star's size has decreased systematically by 15%.
[en] The basic AB problem is to determine how an unshielded tube of magnetic flux Φ affects arbitrarily long-wavelength charged particles impinging on it. For spin 1 at almost all Φ the particles do not penetrate the tube, so the interaction essentially is periodic in Φ (AB effect). Below-threshold bound states move freely only along the tube axis, and consequent induced vacuum currents supplement rather than screen Φ. For a pure magnetic interaction the tube must be broader than the particle Compton wavelength, i.e., only the nonrelativistic spin-1 AB problem exists. copyright 1997 The American Physical Society
[en] Recent developments in the CRANK software suite for experimental phasing have led to many more structures being built automatically. For its first release in 2004, CRANK was shown to effectively detect and phase anomalous scatterers from single-wavelength anomalous diffraction data. Since then, CRANK has been significantly improved and many more structures can be built automatically with single- or multiple-wavelength anomalous diffraction or single isomorphous replacement with anomalous scattering data. Here, the new algorithms that have been developed that have led to these substantial improvements are discussed and CRANK’s performance on over 100 real data sets is shown. The latest version of CRANK is freely available for download at http://www.bfsc.leidenuniv.nl/software/crank/ and from CCP4 (http://www.ccp4.ac.uk/)
[en] The new technique of differential reflectometry was applied to study the characteristics of non-flow corrosive media on the corrosion of copper metal. Differential reflectometry is a form of modulation spectroscopy which measures the normalized difference in reflectivity between two samples, or two adjacent areas of the same sample. In this study, following results have been found. (a) The exact thickness of cuprous oxide film can not be estimated from the intensity of the differential reflectivity at a given wavelength because optical constants for cuprous oxide have not been measured yet. However, it is suggested that the film formed during 69 h of polarization is within about 50 nm thick. (b) Cuprous oxide film grows substantially with time in the first about 45 h of polarization after which the growth is slower
[en] The limiting effects to the stability of optical frequency standards has been assessed. The stability of such a standard depends critically on the spectral width of the atomic absorber. The limiting stability is explored in the absence decoherence (interrogation time limited) and in the more realistic case where optical decoherence and radiative decay are present. The role of motional decoherence in an ion trap system is also discussed. (author)
[en] The infrared (IR) atomic spectral lines that can be observed in laboratory and astrophysical spectra depend both on the atomic structure and the physical conditions in which the atoms reside. This is a brief review of IR laboratory spectroscopy, discussing which lines in the wavelength interval 1-5 μm can be expected to be seen in different astrophysical sources.
[en] Here, distributed feedback (DFB) interband cascade lasers (ICLs) with a 1st order top surface grating were designed and fabricated. Partially corrugated sidewalls were implemented to suppress high order lateral modes. The DFB ICLs have 4 mm long and 4.5 μm wide ridge waveguides and are mounted epi-up on AlN submounts. We demonstrated a continuous-wave (CW) DFB ICL, from a first wafer which has a large detuning of the gain peak from the DFB wavelength, with a side mode suppression ratio of 30 dB. With proper matching of grating feedback and the gain peak wavelength for the second wafer, a DFB ICL was demonstrated with a maximum CW output power and a maximum wall plug efficiency reaching 42 mW and 2%, respectively, at 25 °C. The lasing wavelengths of both lasers are around 3.3 μm at 25 °C.