3,215 research outputs found
Electric Dipole Moments from Stark Effect in Supersonic Expansion: n-Propanol, n-Butanol, and n-Butyl Cyanide
The orientation and magnitude of the molecular electric dipole moment are key properties relevant to topics ranging from the nature of intermolecular interactions to the quantitative analysis of complex gas-phase mixtures, such as chemistry in astrophysical environments. Stark effect measurements on rotational spectra have been the method of choice for isolated molecules but have become less common with the practical disappearance of Stark modulation spectrometers. Their role has been taken over by supersonic expansion measurements within a Fabry-Perot resonator cavity, which introduces specific technical problems that need to be overcome. Several of the adopted solutions are described and compared. Presently, we report precise electric dipole moment determinations for the two most stable conformers of the selected molecules of confirmed or potential astrophysical relevance: n-propanol, n-butanol, and n-butyl cyanide. All dipole moment components have been precisely determined at supersonic expansion conditions by employing specially designed Stark electrodes and a computer program for fitting the measured Stark shifts, inclusive of cases with resolved nuclear quadrupole hyperfine structure. The experimental values are compared with suitable quantum chemistry computations. It is found that, among the tested levels of computation, vibrationally averaged dipole moments are the closest to the observation and the molecular values are, as in the lighter molecules in the series, largely determined by the hydroxyl or nitrile groups
Searching for Bio-Precursors and Complex Organic Molecules in Space using the GBT
Using the latest microwave receiver technology, large organic molecules with abundances as low as approx. 10(exp -11) times that of molecular hydrogen are detectable in cold interstellar clouds via their rotational emission line spectra. We report new observations to search for complex molecules, including molecules of possible pre-biotic importance, using the newly-commissioned Kband focal plane array (KFPA) of the NRAO Robert C. Byrd Green Bank Telescope. Spectra are presented of the dense molecular cloud TMC-1, showing strict upper limits on the level of emission from nitrogen-bearing rings pyrimidine, quinoline and iso-quinoline, carbon-chain oxides C60, C70, HC60 and HC70, and the carbon-chain anion C4H-. The typical RMS brightness temperature noise levels we achieved are approx. 1 mK at around 20 GHz
Laboratory Characterization and Astrophysical Detection of Vibrationally Excited States of Vinyl Cyanide in Orion-KL
New laboratory data of CHCHCN (vinyl cyanide) in its ground and
vibrationally excited states at the microwave to THz domain allow searching for
these excited state transitions in the Orion-KL line survey.
Frequency-modulated spectrometers combined into a single broadband 50-1900 GHz
spectrum provided measurements of CHCHCN covering a spectral range of
18-1893 GHz, whose assignments was confirmed by Stark modulation spectra in the
18-40 GHz region and by ab-initio anharmonic force field calculations. For
analyzing the emission lines of CHCHCN species detected in Orion-KL we used
the excitation and radiative transfer code (MADEX) at LTE conditions. The
rotational transitions of the ground state of this molecule emerge from four
cloud components of hot core nature which trace the physical and chemical
conditions of high mass star forming regions in the Orion-KL Nebula. The total
column density of CHCHCN in the ground state is (3.00.9)x10
cm. We report on the first interstellar detection of transitions in the
v10=1/(v11=1,v15=1) dyad in space, and in the v11=2 and v11=3 states in
Orion-KL. The lowest energy vibrationally excited states of vinyl cyanide such
as v11=1 (at 328.5 K), v15=1 (at 478.6 K), v11=2 (at 657.8 K), the
v10=1/(v11=1,v15=1) dyad (at 806.4/809.9 K), and v11=3 (at 987.9 K) are
populated under warm and dense conditions, so they probe the hottest parts of
the Orion-KL source. Column density and rotational and vibrational temperatures
for CHCHCN in their ground and excited states, as well as for the
isotopologues, have been constrained by means of a sample of more than 1000
lines in this survey. Moreover, we present the detection of methyl isocyanide
(CHNC) for the first time in Orion-KL and a tentative detection of vinyl
isocyanide (CHCHNC) and give column density ratios between the cyanide and
isocyanide isomers.Comment: 46 pages, 22 figures, 14 tables, 9 online table
Ethyl cyanide on Titan: Spectroscopic detection and mapping using ALMA
We report the first spectroscopic detection of ethyl cyanide (CHCN)
in Titan's atmosphere, obtained using spectrally and spatially resolved
observations of multiple emission lines with the Atacama Large
Millimeter/submillimeter array (ALMA). The presence of CHCN in Titan's
ionosphere was previously inferred from Cassini ion mass spectrometry
measurements of CHCNH. Here we report the detection of 27
rotational lines from CHCN (in 19 separate emission features detected
at confidence), in the frequency range 222-241 GHz. Simultaneous
detections of multiple emission lines from HCN, CHCN and CHCCH were
also obtained. In contrast to HCN, CHCN and CHCCH, which peak in
Titan's northern (spring) hemisphere, the emission from CHCN is found
to be concentrated in the southern (autumn) hemisphere, suggesting a distinctly
different chemistry for this species, consistent with a relatively short
chemical lifetime for CHCN. Radiative transfer models show that most of
the CHCN is concentrated at altitudes 300-600 km, suggesting production
predominantly in the mesosphere and above. Vertical column densities are found
to be in the range (2-5) cm.Comment: Published in 2015, ApJL, 800, L1
Search for the QCD Critical Point: Higher Moments of Net-proton Multiplicity Distributions
Higher moments of event-by-event net-proton multiplicity distributions have
been applied to search for the QCD critical point. Model results are used to
provide a baseline for this search. The measured moment products,
and of net-proton distributions, which are directly
connected to the thermodynamical baryon number susceptibility ratio in Lattice
QCD and Hadron Resonance Gas (HRG) model, are compared to the transport and
thermal model results. We argue that a non-monotonic dependence of and as a function of beam energy can be used to search for
the QCD critical point.Comment: 7 pages, 3 figures. CPOD 2010 Proceeding
Formation and photostability of N-heterocycles in space. I. The effect of nitrogen on the photostability of small aromatic molecules
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Taha Toros Arşivi, Dosya No: 21-Burhan Felek. Not: Gazetenin "Geçmiş Zaman Olur ki" köşesinde yayımlanmıştır
The BSUIN project
Baltic Sea Underground Innovation Network (BSUIN) is an European Union funded project that
extends capabilities of underground laboratories. The aim of the project is to join efforts in making
the underground laboratories in the Baltic Sea Region’s more accessible for innovation, business
development and science by improving the availability of information about the underground
facilities, service offerings, user experience, safety and marketing.The development of standards
for the characterization of underground laboratories will allow to compared them with each other.
This will help you choose the best places for physical measurements such as neutrino physics or
searching for dark matter. The project concerns laboratories where so far no measurements have
been made, and even undergrounds where there are no organized laboratories yet.The description
of the BSUIN project and the first results of characterization of natural radioactive background in
underground laboratories will be presented ˙ The BSUIN Project is funded by Interreg Baltic Sea
funding cooperation [2]
Interferometric Imaging of Titan's HC<sub>3</sub>N, H<sup>13</sup>CCCN, and HCCC<sup>15</sup>N
We present the first maps of cyanoacetylene isotopologues in Titan's
atmosphere, including HCCCN and HCCCN, detected in the 0.9 mm
band using the Atacama Large Millimeter/submillimeter array (ALMA) around the
time of Titan's (southern winter) solstice in May 2017. The first
high-resolution map of HCN in its vibrationally excited state is
also presented, revealing a unique snapshot of the global HCN distribution,
free from the strong optical depth effects that adversely impact the
ground-state () map. The HCN emission is found to be strongly enhanced
over Titan's south pole (by a factor of 5.7 compared to the north pole),
consistent with rapid photochemical loss of HCN from the summer hemisphere
combined with production and transport to the winter pole since the April 2015
ALMA observations. The HCCCN/HCCCN flux ratio is derived at the
southern HCN peak, and implies an HCN/HCCCN ratio of .
This represents a significant enrichment in N compared with Titan's main
molecular nitrogen reservoir, which has a N/N ratio of 167, and
confirms the importance of photochemistry in determining the nitrogen isotopic
ratio in Titan's organic inventory.Comment: Accepted for publication in ApJL, May 201
LAGUNA in Polkowice-Sieroszowice mine in Poland
The Polkowice–Sieroszowice mine in one of the seven candidates for the future pan-European underground laboratory studied in the framework of the LAGUNA project. We review the evidence that from the point of view
of geology, long-term plans for the mine and existing infrastructure, and support of the authorities this is a perfect place to host the 100 kton liquid argon detector GLACIER
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