187,016 research outputs found
Astronomical Applications Of New Line Lists For Cn, C2 And Their Isotopologues
No full textFor cool stellar and substellar objects, atomic lines weaken, and detailed elemental and isotopic abundances are often derived from molecular absorption features. We have embarked on a project to provide molecular line lists by combining experimental observations for line positions with ab initio calculations for line strengths. So far we have results for MgH (A-X and B-X transitions)\footnote{E. GharibNezhad, A. Shayesteh and P. F. Bernath, Mon. Notices R. Astro. Soc. 432, 2043-2047 (2013)}\footnote{K. H. Hinkle, L. Wallace, R. S. Ram, P. F. Bernath, C. Sneden and S. Lucatello, Astrophys. J. Suppl. 207, 26 (7pp) (2013)}, C (Swan system)\footnote{J. S. A. Brooke, P. F. Bernath, T. W. Schmidt and G. B. Bacskay, J. Quant. Spectrosc. Rad. Trans. 124, 11-20 (2013)}\footnote{R. S. Ram, J. S. A. Brooke, P. F. Bernath, C. Sneden and S. Lucatello, Astrophys. J. Suppl. 211, 5 (7pp) (2014)}, CN (red and violet systems)\footnote{J. S. A. Brooke, R. S. Ram, C. M. Western, G. Li, D. W. Schwenke and P. F. Bernath, Astrophys. J. Suppl. 210, 23 (15pp) (2014)}, CP (A-X transition)\footnote{R. S. Ram, J. S. A. Brooke, C.M. Western and P. F. Bernath, J. Quant. Spectrosc. Rad. Transfer (in press)}, NH (vibration-rotation bands) and OH (Meinel system)\footnote{J. S. A. Brooke et al., this meeting, P301}. This talk will briefly describe the new line lists for the Swan system (d-a) of C and CC, and the red (A-X) and violet (B-X) systems of CN, CN and CN. Applications to the spectra of carbon-enhanced metal-poor stars, the K-giant Arcturus, the metal-rich open cluster NGC 6791, the Sun and comets will be presented.Made available in DSpace on 2014-09-17T16:56:06Z (GMT). No. of bitstreams: 3
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Previous issue date: 2014-06-17Made available in DSpace on 2015-04-14T18:36:41Z (GMT). No. of bitstreams: 4
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Previous issue date: 2014-06-1
CRIRES spectroscopy and empirical line-by-line identification of FeH molecular absorption in an M dwarf
No full textMolecular FeH provides a large number of sharp and isolated absorption lines that can be
used to measure radial velocity, rotation, or magnetic field strength with high accuracy.
Our aim is to provide an FeH atlas for M-type stars in the spectral region from 986 nm to
1077 nm (Wing-Ford band). To identify these lines in CRIRES spectra of the magnetically
inactive, slowly rotating, M5.5 dwarf GJ1002, we calculated model spectra for the selected
spectral region with theoretical FeH line data. In general this line list agrees with the
observed data, but several individual lines differ significantly in position or in line
strength. After identification of as many as possible FeH lines, we corrected the line
data for position and line strength to provide an accurate atlas of FeH absorption lines
for use in high precision spectroscopy of low mass stars. For all lines, we used a Voigt
function to obtain their positions and equivalent widths. Identification with theoretical
lines was done by hand. For confirmation of the identified lines, we used statistical
methods, cross-correlation techniques, and line intensities. Eventually, we were able to
identify FeH lines from the (0,0), (1,0), (1,1), (2,1), (2,2), (3,2), and (4,3)
vibrational bands in the observed spectra and correct the positions of the lines if
necessary. The deviations between theoretical and observed positions follow a normal
distribution approximately around zero. In order to empirically correct the line strength,
we determined Teff, instrumental broadening (rotational
broadening) and a van der Waals enhancement factor for the FeH lines in GJ1002. We also
give the scaling factors for the Einstein A values to correct the line strengths. With the
identified lines, we derived rotational temperatures from the line intensities for GJ1002.
We conclude that FeH lines can be used for a wide variety of applications in astrophysics.
With the identified lines it will be possible for example to characterize magnetically
sensitive or very temperature sensitive lines, which can be used to investigate M-type
stars
HIGH RESOLUTION FOURIER TRANSFORM INFRARED SPECTROSCOPY OF THE TRANSITION OF CP.
No full textAuthor Institution: Department of Chemistry, University of Arizona; Department of Chemistry, University of WaterlooThe near infrared emission spectrum of - transition of CP has been recorded using a Fourier transform spectrometer. The rotational structure of six new bands involving vibrational levels up to v=4 of both electronic states has been analyzed. The RKR potential energy curves for the and electronic states have also been evaluated. This extends our previous works on . R.S. Ram and P.F. Bernath, J. Mol Spectrosc 122 282 (1987)
Study of infrared emission spectroscopy for the B1∆G-A1ΠU AND B′1ΣG+-A1ΠU systems of c2
No full textRecently, we carried out the perturbation analysis of C spectra and identified forbidden singlet-triplet intersystem transitions,\footnote{W. Chen, K. Kawaguchi, P. F. Bernath, and J. Tang, \it{J. Chem. Phys.}, \bf{142}, \rm 064317 (2015).} which aroused further interest in other C spectra for the many low-lying electronic states of this fundamental molecule.
In 1988, the - and - band systems were discovered by Douay et al.,\footnote{M. Douay, R. Nietmann and P. F. Bernath, \it{J. Mol. Spectrosc.}, \bf{131}, \rm 261 (1988).} who observed eight bands of the - system with v up to 5 for the state and six bands of the - system with v up to 3 for the state in the Fourier transform infrared emission spectra of hydrocarbon discharges.
In the work presented here, we identified twenty-four bands of the two systems, among which the v = 4 and the v = 6, 7 and 8 vibrational levels involved in nine bands were studied for the first time. A direct global analysis with Dunham parameters was carried out satisfactorily for the - system except for a small perturbation in the v = 6 level. The calculated rovibrational term energies up to v = 12 showed that the level crossing between the and states is responsible for many of the prominent perturbations in the Swan system observed previously.\footnote{A. Tanabashi, T. Hirao, T. Amano and P. F. Bernath, \it{Astrophys. J. Suppl. Ser.}, \bf{169}, \rm 472 (2007).} Nineteen lines of the - forbidden transitions were identified and the off-diagonal spin-orbit interaction constant between and was derived as 8.3(1) \wn. For the - system, only individual band analyses for each vibrational level in the state could be done satisfactorily and Dunham parameters obtained from these effective parameters showed that the anharmonic vibrational constant is anomalously small (nearly zero). Inspection of the RKR potential curves for the and states revealed that an avoided crossing may occur around 30000 \wn, which is responsible for the anomalous molecular constants in these two states.\footnote{W. Chen, K. Kawaguchi, P. F. Bernath, and J. Tang, \it{J. Chem. Phys.}, \bf{144}, \rm 064301 (2016).}Made available in DSpace on 2017-01-26T21:38:48Z (GMT). No. of bitstreams: 3
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Previous issue date: 2016-06-2
HIGH RESOLUTION FOURIER TRANSFORM EMISSION SPECTROSCOPY OF CP AND PH
No full textAddress of Ram and Bernath: Department of Chemistry, University of Arizona, Tucson, Arizona 85721.Author Institution:The vibration-rotation spectrum of PH and the electronic transition of CP were recorded in the infrared with the Fourier transform spectrometer associated with the McMath Solar Telescope at Kitt Peak. CP and PH were made in a microwave discharge of vapor and . The carbon required to make CP was present as a deposit on the discharge tube walls. The 1-0, 2-1 and 3-2 and 4-3 vibration-rotation bands of the state of PH were observed and molecular constants extracted. For CP the 0-0, 1-0, 3-1, 0-1, 0-2 bands of the transition were observed from . The A-X transition of CP is analogous to the red system of CN
Stratospheric Aerosol Composition Observed By The Atmospheric Chemistry Experiment Following The 2019 Raikoke Eruption
No full textFollowing the eruption of the Raikoke volcano in 2019, infrared spectra from the Atmospheric Chemistry Experiment satellite were used to evaluate the composition of stratospheric aerosols in the Northern Hemisphere. The layer of aerosols observed after the eruption ranged from 9 to 20 km in altitude and persisted in the stratosphere for several months. This layer was composed nearly entirely of sulfate aerosols, droplets of a mixture of sulfuric acid and water. To determine the aerosol composition, the spectra were modeled using extinction values calculated with Mie scattering code and sulfuric acid optical constants. Contrary to previous reports, there is no evidence of stratospheric smoke being present in the Arctic region.
P. F. Bernath. The Atmospheric Chemistry Experiment (ACE). JQSRT 2017;186:3-16. https://doi.org/10.1016/j.jqsrt.2016.04.006
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Atlas Of Ace Spectra Of Clouds And Aerosols
No full textClouds and aerosols play a vital role in the Earth’s climate. Detecting polar mesospheric clouds, polar stratospheric clouds and aerosols is useful for monitoring climate change and atmospheric chemistry. ACE satellite data is used to provide an infrared spectral atlas of polar mesospheric clouds, three types of polar stratospheric clouds (nitric acid trihydrate, sulfuric/nitric acid ternary solutions, and ice), cirrus clouds, smoke from fires, and sulfate aerosols. Nearly all example spectra have been modeled with either Mie scattering or T-matrix codes using the appropriate optical constants.
P. F. Bernath. The Atmospheric Chemistry Experiment (ACE). JQSRT 2017;186:3-16. https://doi.org/10.1016/j.jqsrt.2016.04.006
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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