687 research outputs found
GPRD, A Database for the Spectral Properties of Diatomic Molecules of Atmospheric Interest
A short note describing the development of a database providing factual and
numerical data on the spectral properties of diatomic molecules. This database
is available online for the overall scientific community at the following
adress: http://cfp.ist.utl.pt/radiation/Comment: 2 page
Hot methane line lists for exoplanet and brown dwarf atmospheres
We present comprehensive experimental line lists of methane (CH4) at high
temperatures obtained by recording Fourier transform infrared emission spectra.
Calibrated line lists are presented for the temperatures 300 - 1400 degC at
twelve 100 degC intervals spanning the 960 - 5000 cm-1 (2.0 - 10.4 microns)
region of the infrared. This range encompasses the dyad, pentad and octad
regions, i.e., all fundamental vibrational modes along with a number of
combination, overtone and hot bands. Using our CH4 spectra, we have estimated
empirical lower state energies (Elow in cm-1) and our values have been
incorporated into the line lists along with line positions (cm-1) and
calibrated line intensities (S' in cm molecule-1). We expect our hot CH4 line
lists to find direct application in the modeling of planetary atmospheres and
brown dwarfs.Comment: Supplementary material is provided via the Astrophysical Journal
referenc
Spectroscopic Constants and Line Positions for TiO Singlet States
consistent set of spectroscopic constants for the a1Î,d1ÎŁ+,b1Î ,c1Ί, and f1Î states of 48Ti16O has been determined from analysis of the b1Î âa1Î,b1Î âd1ÎŁ+,c1Ίâa1Î, and f1Îâa1Î systems. Three Fourier transform emission spectra have been used for the analysis. New bands of the b1Î âa1Î and c1Ίâa1Î systems have been fitted. The first analysis of the c1Ίâa1Î system using Fourier transform spectra is also provided. Extensive and improved line positions are measured. TiO is prominent in the spectra of oxygen-rich cool stellar objects and may be present in hot-Jupiter exoplanet atmospheres
Line Lists for LiF and LiCl in the X1ÎŁ+ Ground State
Vibrationârotation line lists for 6LiF, 7LiF, 6Li35Cl, 6Li37Cl, 7Li35Cl, and 7Li37Cl in the X1ÎŁ+ ground states have been prepared. The rovibrational energy levels have been calculated using potential energy surfaces determined by direct potential-fitting employing the rotational and rovibrational transition frequencies of all isotopologues, and required the inclusion of BornâOppenheimer breakdown terms. Dipole moment functions calculated ab initio at the MRCI/aug-cc-pwCV5Z level have been used for line strength calculations. Partition functions for temperatures up to 5000 K have been calculated. LiF and LiCl are predicted to be present in the atmospheres of hot rocky exoplanets, brown dwarfs, and cool stars
Pyrocumulonimbus Stratospheric Plume Injections Measured by the ACEâFTS
The Atmospheric Chemistry Experiment (ACE) is a satelliteâbased mission that probes Earth\u27s atmosphere via solar occultation. The primary instrument on board is a highâresolution infrared Fourier transform spectrometer (Atmospheric Chemistry Experiment Fourier Transform Spectrometer, ACEâFTS), providing altitudeâresolved volume mixing ratio measurements for numerous atmospheric constituents, including many biomass burning products. The ACE mission has observed the aftermath of three major pyrocumulonimbus events, in which extreme heat from intense fires created a pathway for directly injecting into the stratosphere plumes of gaseous and aerosol pollutants. These three events were associated with severe Australian bushfires from 2009 and 2019/2020, along with intense North American wildfires from summer 2017. The ACEâFTS measured stratospheric plumes containing aerosols, enhanced levels of gaseous fire products, and tropospheric air transported into the stratosphere. Infrared spectral features indicate strikingly similar aerosol composition for all three events, characteristic of oxygenated organic matter
Line Strengths of Rovibrational and Rotational Transitions in the X Ground State of OH
A new line list including positions and absolute intensities (in the form of
Einstein values and oscillator strengths) has been produced for the OH
ground X\DP\ state rovibrational (Meinel system) and pure rotational
transitions. All possible transitions are included with v\primed and
v\Dprimed up to 13, and up to between 9.5 and 59.5, depending on the
band. An updated fit to determine molecular constants has been performed, which
includes some new rotational data and a simultaneous fitting of all molecular
constants. The absolute line intensities are based on a new dipole moment
function, which is a combination of two high level ab initio calculations. The
calculations show good agreement with an experimental v=1 lifetime,
experimental values, and v=2 line intensity ratios
from an observed spectrum. To achieve this good agreement, an alteration in the
method of converting matrix elements from Hund's case (b) to (a) was made.
Partitions sums have been calculated using the new energy levels, for the
temperature range 5-6000 K, which extends the previously available (in HITRAN)
70-3000 K range. The resulting absolute intensities have been used to calculate
O abundances in the Sun, Arcturus, and two red giants in the Galactic open and
globular clusters M67 and M71. Literature data based mainly on [O I] lines are
available for the Sun and Arcturus, and excellent agreement is found.Comment: 17 pages, 8 figues. 7 supplementary files: dipole moment functions
(OH-X-DMFs.txt), equilibrium constants (OH-X-Equilibrium_Constants.txt),
partition function (OH-X-Q_5-6000K.dat), PGOPHER file with molecular
constants and transition matric elements (OH-XX.pgo), vibrational Einstein A
and f values (OH-XX-Avv_fvv.txt), line list (OH-XX-Line_list.txt), and
OH-Transformation_Equation_Extra.doc
Balloon-borne radiometer measurement of Northern Hemisphere mid-latitude stratospheric HNO3 profiles spanning 12 years
Low-resolution atmospheric thermal emission spectra collected by balloon-borne radiometers over the time span of 1990â2002 are used to retrieve vertical profiles of HNO3, CFC-11 and CFC-12 volume mixing ratios between approximately 10 and 35 km altitude. All of the data analyzed have been collected from launches from a Northern Hemisphere mid-latitude site, during late summer, when stratospheric dynamic variability is at a minimum. The retrieval technique incorporates detailed forward modeling of the instrument and the radiative properties of the atmosphere, and obtains a best fit between modeled and measured spectra through a combination of onion-peeling and global optimization steps. The retrieved HNO3 profiles are consistent over the 12-year period, and are consistent with recent measurements by the Atmospheric Chemistry Experiment-Fourier transform spectrometer satellite instrument. This suggests that, to within the errors of the 1990 measurements, there has been no significant change in the HNO3 summer mid-latitude profile
Improved Ultraviolet and Infrared Oscillator Strengths for OH+
Molecular ions are key reaction intermediates in the interstellar medium. OH+ plays a central role in the formation of more complex chemical species and for estimating the cosmic ray ionization rate in astrophysical environments. Here, we use a recent analysis of a laboratory spectrum in conjunction with ab initio methods to calculate infrared and ultraviolet oscillator strengths. These new oscillator strengths include branch dependent intensity corrections, arising from the HermanâWallis effect, that have not been included before. We estimate 10% total uncertainty in the UV and 6% total uncertainty in the IR for the oscillator strengths
Spectroscopic Constants, Abundances, and Opacities of the TiH Molecule
Using previous measurements and quantum chemical calculations to derive the
molecular properties of the TiH molecule, we obtain new values for its
ro-vibrational constants, thermochemical data, spectral line lists, line
strengths, and absorption opacities. Furthermore, we calculate the abundance of
TiH in M and L dwarf atmospheres and conclude that it is much higher than
previously thought. We find that the TiH/TiO ratio increases strongly with
decreasing metallicity, and at high temperatures can exceed unity. We suggest
that, particularly for subdwarf L and M dwarfs, spectral features of TiH near
0.52 \mic, 0.94 \mic, and in the band may be more easily measureable
than heretofore thought. The recent possible identification in the L subdwarf
2MASS J0532 of the 0.94 \mic feature of TiH is in keeping with this
expectation. We speculate that looking for TiH in other dwarfs and subdwarfs
will shed light on the distinctive titanium chemistry of the atmospheres of
substellar-mass objects and the dimmest stars.Comment: 37 pages, including 4 figures and 13 tables, accepted to the
Astrophysical Journa
CH in stellar atmospheres: an extensive linelist
The advent of high-resolution spectrographs and detailed stellar atmosphere
modelling has strengthened the need for accurate molecular data.
Carbon-enhanced metal-poor (CEMP) stars spectra are interesting objects with
which to study transitions from the CH molecule. We combine programs for
spectral analysis of molecules and stellar-radiative transfer codes to build an
extensive CH linelist, including predissociation broadening as well as newly
identified levels. We show examples of strong predissociation CH lines in CEMP
stars, and we stress the important role played by the CH features in the
Bond-Neff feature depressing the spectra of barium stars by as much as 0.2
magnitudes in the 3000 -- 5500 \AA\ range. Because of the extreme
thermodynamic conditions prevailing in stellar atmospheres (compared to the
laboratory), molecular transitions with high energy levels can be observed.
Stellar spectra can thus be used to constrain and improve molecular data.Comment: 33pages, 15 figures, accepted in A&A external data available at
http://www.astro.ulb.ac.be/~spectrotools
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