Search results for "Maser"
showing 6 items of 16 documents
Rotational excitation of mono- and doubly-deuterated water by hydrogen molecules
2011
Rate coefficients for rotational transitions in HDO and D2O induced by H2 collisions below 300 K are presented. Calculations have been performed at the close-coupling and coupledstates levels with the deuterated variants of the H2O–H2 interaction potential of Valiron et al. The HDO–H2 and D2O–H2 rate coefficients are compared to the corresponding rate coefficients for HDO–He and H2O–H2, respectively. Significant differences are observed. In particular the new HDO rate coefficients are found to be significantly larger (by up to three orders of magnitude) than the corresponding HDO–He rate coefficients. The impact of the new HDO rate coefficients is examined with the help of non-LTE radiative…
Hydrogen maser frequency shifts due to coherently excited Δm F =±1 transitions betweenF=1 levels of the atomic hydrogen ground state
1968
Hydrogen maser frequency shifts, caused by the multiple quantum transition nonlinearities of a resonant multiple frequency excitation of the atomic hydrogen four level ground state system have been investigated. The oscillation characteristics of hydrogen maser operation with simultaneously excited, low frequencyΔm F =±1 transitions between theF=1 states of the atomic hydrogen ground state have been analysed theoretically and explicit formulas for hydrogen maser frequency shifts and amplitude response have been derived for arbitrary maser oscillation amplitude and a small signal approximation for theΔm F =±1 “Zeeman” transitions. The comparison with experimentally observed hydrogen maser fr…
Towards an Understanding of the Dynamics of the Milky Way
2005
Determination of outer rotation curve using Galactic masers The rotation curve of the Galaxy is poorly determined outside the solar circle (e.g. Honma & Sofue 1997). The situation makes difficult to derive the dynamical mass of the Galaxy, which is essential for inferring the amount of Galactic dark gravitating matter. We selected Galactic masers in this study since they distributed over the whole Galaxy. Moreover, they can observed with VLBI at extremely high angular resolution, allowing a measurement of the annual parallax, and thus the source’s distance, and its proper motion due to Galactic rotation with phase referencing VLBI astrometric observation. We have already performed phase-ref…
Accumulation of entanglement in a continuous variable memory
2007
We study the accumulation of entanglement in a memory device built out of two continuous variable (CV) systems. We address the case of a qubit mediating an indirect joint interaction between the CV systems. We show that, in striking contrast with respect to registers built out of bidimensional Hilbert spaces, entanglement superior to a single ebit can be efficiently accumulated in the memory, even though no entangled resource is used. We study the protocol in an immediately implementable setup, assessing the effects of the main imperfections.
Phase Reference VLBI Astrometry for Mira-Type Stars
2003
We carried out phase reference VLBI observations at 43 GHz between SiO masers in Mira type variables and adjacent extragalactic continuum source with VLBA. Main aim of this observation is determination of spatial distribution between SiO maser spots at v = 1 and v = 2, J=l→0 transition. Although the standard calibration was successful for each source, the phase reference calibration have not been successful. However, we will determine the absolute positional difference of each SiO maser spot within about 1 milli arcsecond due to the structure effect of reference source if the phase reference VLBI is successful
The kinematics of water masers in the stellar molecular outflow source, IRAS 19134+2131
2004
Using the Very Large Array (VLA) and the Very Long Baseline Array (VLBA), we have observed water maser emission in the proto-planetary nebula candidate IRAS 19134+2131, in which the water maser spectrum has two groups of emission features separated in radial velocity by ∼100 km s^−1. The blue-shifted and red-shifted clusters of maser features are clearly separated spatially by ∼150 mas, indicative of a fast collimated flow. However, not all of the maser features are aligned along the axis of the flow, as is seen in the similar high-velocity water maser source, W43A. Comparing the VLA and VLBA maps of the water maser source, we find 4 maser features that were active for 2 years. Using only V…