46 research outputs found
Spectroscopic parameters for silacyclopropynylidene, SiC, from extensive astronomical observations toward CW Leo (IRC +10216) with the Herschel satellite
A molecular line survey has been carried out toward the carbon-rich
asymptotic giant branch star CW Leo employing the HIFI instrument on board of
the Herschel satellite. Numerous features from 480 GHz to beyond 1100 GHz could
be assigned unambiguously to the fairly floppy SiC molecule. However,
predictions from laboratory data exhibited large deviations from the observed
frequencies even after some lower frequency data from this survey were
incorporated into a fit. Therefore, we present a combined fit of all available
laboratory data together with data from radio-astronomical observations.Comment: 7 pages, 1 figure, J. Mol. Spectrosc., appeared; CDMS links corrected
(version 2; current version: 3; may be updated later this year
Astronomical identification of CN-, the smallest observed molecular anion
We present the first astronomical detection of a diatomic negative ion, the
cyanide anion CN-, as well as quantum mechanical calculations of the excitation
of this anion through collisions with para-H2. CN- is identified through the
observation of the J = 2-1 and J = 3-2 rotational transitions in the C-star
envelope IRC +10216 with the IRAM 30-m telescope. The U-shaped line profiles
indicate that CN-, like the large anion C6H-, is formed in the outer regions of
the envelope. Chemical and excitation model calculations suggest that this
species forms from the reaction of large carbon anions with N atoms, rather
than from the radiative attachment of an electron to CN, as is the case for
large molecular anions. The unexpectedly large abundance derived for CN-, 0.25
% relative to CN, makes likely its detection in other astronomical sources. A
parallel search for the small anion C2H- remains so far unconclusive, despite
the previous tentative identification of the J = 1-0 rotational transition. The
abundance of C2H- in IRC +10216 is found to be vanishingly small, < 0.0014 %
relative to C2H.Comment: 5 pages, 4 figures; accepted for publication in A&A Letter
A line confusion limited millimeter survey of Orion KL. II: Silicon-bearing species
We present a study of the Silicon-bearing species detected in a line
confusion limited survey towards Orion KL performed with the IRAM 30-m
telescope, which ranges from 80 to 280 GHz. Our aim is to derive physical and
chemical conditions for each family taking into account all observed lines from
all isotopologues of each species. We have modeled the lines of the detected
molecules using a radiative transfer code, which permit us to choose between
LVG and LTE approximations depending on the physical conditions of the gas. We
have used appropriate collisional rates for the LVG calculations. For the v=1
state of SiO we have detected the J=2-1 line and, for the first time in this
source, emission in the J=4-3 transition, both of them showing strong masering
effect. For SiO v=0, we have detected 28SiO, 29SiO, and 30SiO; in addition, we
have mapped the J = 5-4 SiO line. For SiS, we have detected the main species,
29SiS, and SiS v=1. Unlikely other species detected in Orion KL (IRc2), the
emission peak of SiS appears at a velocity of ~15.5 km s-1; a study of the 5-4
SiO line around IRc2 shows this feature as an extended component that probably
arises from the interaction of the outflow with the ambient cloud. We derive a
SiO/SiS column density ratio of ~13 in the plateau component. Besides, we
provide upper limits to the column density of several non-detected
Silicon-bearing species. The results of our chemical models show that while it
is possible to reproduce SiO in the gas phase (as well as on the grains), SiS
is a product of surface reactions, most likely involving direct reactions of S
with Si.Comment: Astronomy and Astrophysics, in pres
Machine Translation Using Bilingual Term Entries Extracted From Parallel Texts
Patent summaries are machine-translated using bilingual term entries extracted from parallel texts for evaluation. The result shows that bilingual term entries extracted from 2,000 pairs of parallel texts which share a specific domain with the input texts introduce more improvements than a technical term dictionary with 38,000 entries which covers a broader domain. The result also shows that only 10 pairs of parallel texts found by similar document retrieval have comparable effects to the technical term dictionary, suggesting that parallel texts to be used do not need to be classified into fields prior to term extraction