Results 1 - 10 of 1864
Results 1 - 10 of 1864. Search took: 0.025 seconds
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[en] Wall shift limits the actual accuracy of the hydrogen maser to 10-12. After a review of the perturbation of the hydrogen atoms upon collision on the surface of teflon coated bulb, a new approach is proposed in which a teflon cylinder replaces the classical storage bulb. In this case a more reproducible wall shift is expected. (author)
[en] We present the first interferometric observations at 18.5 GHz of IRS 1 in NGC 7538. These observations include images of the nonmetastable 14NH3 (9, 6) masers with a synthesized beam of 2 arcsec and images of the continuum emission with a synthesized beam of 150 mas. Of the maser emission, the previously known feature near v LSR = -60 km s-1 is spectrally resolved into at least two components and we observe several new maser emission features near v LSR = -57 km s-1. The new maser emission near -57 km s-1 lies 250 ± 90 mas northwest of the maser emission near -60 km s-1. All of the masers are angularly unresolved indicating brightness temperatures TB > 2000 K. We are also able to conclusively associate the ammonia masers with the position of IRS 1. The excitation of these rare ammonia masers is discussed in the context of the rich maser environment of IRS 1.
[en] The reasons for the differences between extremely powerful extragalatic water masers (EPEWMs) and strong Galactic H2O masers are discussed. This model quite successfully explains many important characteristics of EPEWMs; the rapid time variations, the broad range and random velocity distribution, the extremely high luminosities, the various heights or widths of features in spectra, the strong infrared radiation from the galaxies, how an active nucleus contributes to an EPEWM, how some parts of EPEWMs producing strong features are pumped, why this pump mechanism can work, and why EPEWMs are different from strong Galactic H2O masers. Recent observations of extragalactic water masers which have extremely high luminosities raise the possibility that the stimulated emission rate in the maser emission line in these regions is much higher than in Galactic masers. It is possible that the local stimulated emission rate exceeds the local bandwidth for the radiation. In this case the standard expression relating the photon emission rate to the profile averaged mean intensity does not apply. A new expression for the photon emission rate is derived
[en] We present a catalogue of stellar objects with 1612 MHz maser emission extracted from the literature published between 1963 and 1983. A total of 442 sources were found. Some unpublished data are also included. A nearly full reference list (updated to 1987) is given. We discuss briefly the nature of the sources
[en] An average Hamiltonian, which contains pair - atomic effects, is used to develop a theory of the Micromaser. A modified master equation is derived and both a steady - state and a time - dependent solutions are found showing that the trapping conditions are disturbed by influence of two-atomic events. An approximate as well as an exact spectrum are calculated and narrowing of linewidth is demonstrated within the framework of presented theory. (Authors)
[en] A coaxial localized-defect Bragg resonator has potential applications in high-power CARM oscillators. When it operates at sub-terahertz and terahertz frequencies, a higher-order mode is always required so as to get enough large geometry size. Analysis shows that higher-order mode operation may cause undesired mode competition due to the localized defect coupling the operating mode with its neighboring modes. A simple but efficient method is presented to solve the mode competition problem, where Hamming windowing-function distribution is separately applied to both sides of the localized defect.
[en] The relativistic equation which describes the electron movement, of an annular section beam, in the electromagnetic field of a cylindrical waveguide that operates in TE sub (021) mode is numerically solved. The energy exchange processes between the beam and RF fields are investigated, calculating the electron energy into the cavity. The energy extracted by electromagnetic fields of resonance cavities is provided from crossed energy of electron rotation. (M.C.K.)
[pt]A equacao relativistica que descreve o movimento dos eletrons, de um feixe de seccao anelar, no campo eletromagnetico de um guia de onda cilindrico que opera no modo TE021 e resolvida numericamente. Calculando a energia dos eletrons ao longo da cavidade, sao investigados os processos de troca de energia entre o feixe e os campos de RF. Verifica-se que a energia extraida pelos campos eletromagneticos da cavidade ressoadora provem da energia transversal de rotacao dos eletrons. (autor)
[en] We report the first interferometric detection of 183 GHz water emission in the low-mass protostar Serpens SMM1 using the Submillimeter Array with a resolution of 3'' and rms of ∼7 Jy in a 3 km s-1 bin. Due to the small size and high brightness of more than 240 Jy beam-1, it appears to be maser emission. In total, three maser spots were detected out to ∼700 AU from the central protostar, lying along the redshifted outflow axis, outside the circumstellar disk but within the envelope region as evidenced by the continuum measurements. Two of the maser spots appear to be blueshifted by about 1-2 km s-1. No extended or compact thermal emission from a passively heated protostellar envelope was detected with a limit of 7 Jy (16 K), in agreement with recent modeling efforts. We propose that the maser spots originate within the cavity walls due to the interaction of the outflow jet with the surrounding protostellar envelope. Hydrodynamical models predict that such regions can be dense and warm enough to invert the 183 GHz water transition.