238 research outputs found
Temperature-dependence of self- and air-broadened CO line shapes in the fundamental band
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Previous issue date: 2019-06-21"We present results of an extensive analysis of the CO 10 band in 40 spectra of pure carbon monoxide and carbon monoxide mixed with air recorded at temperatures ranging between 79 K and room temperature. All spectra were recorded using the 1-m McMath-Pierce Fourier Transform spectrometer located at Kitt Peak, AZ, USA and two temperature-controlled gas cells.
The analysis was carried out using multispectrum fitting software\footnote{D.~C.~Benner,
C.~P.~Rinsland, V.~Malathy Devi, M.~A.~H.~Smith and
D.~A.~Atkins, \textit{JQSRT} \underline{\textbf{53}} (1995) 705-721.} and the Voigt, speed-dependent Voigt and Rautian line shape models. When using the Rautian model, we employed calculated narrowing parameters obtained from computed diffusion constants\footnote{J.~O.~Hirschfelder, C.~F.~Curtiss and R.~B.~Bird, \underline{Molecular theory of gases and liquids}, New York, Wiley and Sons, 1952.} for each of the absorber-perturber pairs CO-CO, CO-N and CO-O.
The experimentally retrieved temperature dependences of the line shape parameters are been compared with previous published results and with the results of calculations for CO-N.
We thank D.~Chris Benner for the Labfit software. The work of V.~M.~Devi was funded by NASA grants and contracts, and the research by M.~A.~H.~Smith was performed as part of her former employment at NASA Langley Research Center. No official endorsements are intended or implied. N.~Islam and A.~Predoi-Cross have been funded by NSERC. S.~Ivanov received financial support from the Ministry of Science and Higher Education within the State assignment FSRC ""Crystallography and Photonics"" RAS and Russian Science Foundation (Project No.18-55-16006).
The far-infrared spectrum of 12C2HD
No full textThe infrared spectrum of 12C2HD has been studied using synchrotron radiation at the far-infrared beam line, Canadian Light Source, Saskatoon, Canada. The spectra were recorded at a resolution of 0.00096 cm-1 in the 60 to 360 cm-1 range using a Bruker IFS 125 Fourier transform spectrometer. In total, 821 vibration rotation lines were observed and assigned to the P(J), Q(J) and R(J) transitions of the v 5←v4 difference band and associated hot bands with J up to 35 and (v4+v5) up to 3. These new transitions were analysed together with 4518 transitions involving bending states with (v I+v5) up to 3 available in the literature. The spectroscopic parameters obtained from the fit reproduce 4909 transitions with a standard deviation of 0.00028 cm-1. The v5←v 4 bands of 13CH12CD and 12CH 13CD were also detected and analysed. © 2011 Taylor & Francis.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Spectroscopic study of air-broadened nitrous oxide in the ν3 band
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Previous issue date: 6We present results of a recent analysis of laboratory spectra to determine line positions, intensities, _x000d_
air-broadened half-widths and pressure-induced shifts and their temperature dependences _x000d_
in the fundamental band of NO. The spectra used in this study were recorded using _x000d_
the 1-m McMath-Pierce Fourier transform spectrometer while it was located at the National Solar _x000d_
Observatory on _x000d_
Kitt Peak, AZ. Multispectrum analysis softwarefootnote{D.~C.~Benner, C.~P.~Rinsland, _x000d_
V.~Malathy Devi, M.~A.~H.~Smith, D.~Atkins, textit{JQSRT} _x000d_
textbf{53} (1995) 705-721.} was used to retrieve the line parameters using the Voigt _x000d_
and speed-dependent Voigt line profiles. The line mixing coefficients were calculated using the _x000d_
Exponential Power Gap scaling law. Comparisons with similar published results will be presented
SELF-AND -BROADENING AND SHIFT COEFFICIENTS IN THE BAND OF : REVISITED
No full textD. Chris Benner, C. P. Rinsland, V. Malathy Devi, M. A. H. Smith and D. Atkins, JQSRT 53, 705-721 (1995). V. Malathy Devi, D. Chris Benner, M. A. H. Smith, C. P. Rinsland and A. W. Mantz, JQSRT 75, 455-471 (2002).Author Institution: Department of Physics, The College of William and Mary; Department of Physics, The University of Lethbridge; Atmospheric Sciences, NASA Lang-ley Research Center; Department of Physics, Astronomy and Geophysics, Connecticut CollegeRoom temperature values for self-broadened and hydrogen-broadened Lorentz half width coefficients, and self and hydrogen pressure-induced shift coefficients have been measured for transitions with rotational quantum number index m ranging from -24 to +24 in the band of . The spectra were recorded with the McMath-Pierce Fourier transform spectrometer located at the National Solar Observatory on Kitt Peak. The analysis was performed using a multispectrum nonlinear least squares modified to constrain the Lorentz widths in the P and R branches to be identical for the same value. We have compared the present results with our previous measurements made with the same and with other measurements published recently
Physico-chemical characteristics and antimicrobial studies of silver doped hydroxyapatite
No full text"New Measurements And Assignments In The V<sub>t</sub> = 0, 1, 2 Torsional States Of <span Class=""roman"">cd</span><sub><span Class=""roman"">3</span></sub><span Class=""roman"">oh</span> And <span Class=""roman"">ch</span><sub><span Class=""roman"">3</span></sub><"
No full text"We present\footnote{This work was done under support of the Deutsche Forschungsgemeinschaft and Volkswagen foundation. The assistance of Science and Technology Center in Ukraine is acknowledged (STCU partner project P756).} the results of our new study of the torsion-rotation spectra of the two deuterated isotopologues of methanol: \chem{CD_3OH} and \chem{CH_3OD}. The new microwave measurements were carried out from the millimeter wave range (starting at 34 GHz) to the THz range (up to 1.1 THz) using spectrometers in Kharkiv and K{\""o}ln. The new measurements in the FIR range were carried out in Braunschweig for \chem{CD_3OH} from 20 to 900 \wn. In this work we significantly extend the rotational quantum number coverage for both isotopologues (from = 26 [1] to = 55 for \chem{CD_3OH} and from =21 [2] to =40 for \chem{CH_3OD}). The analysis is done using the rho axis method and the RAM36 program code. Our preliminary fits show that for both isotopologs the v = 2 torsional state is significantly affected by intervibrational interactions with non-torsional vibrational modes which propagate down through intertorsional interactions. At the same time, for \chem{CD_3OH} we were able to get a fit within experimental error for v = 0, 1 states. For \chem{CH_3OD} analysis is in progress now. In the talk the details of this new study will be discussed.
[1] A. Predoi-Cross, Li-Hong Xu, M.S. Walsh, R.M. Lees, M. Winnewisser, and H. Lichau J. Mol. Spectrosc.188, 94–101 (1998).
[2] Y.-B. Duan, I. Ozier, S. Tsunekawa, and K. Takagi, J. Mol. Spectrosc. 218 (2003) 95–107."Made available in DSpace on 2021-09-24T21:09:19Z (GMT). No. of bitstreams: 2
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Previous issue date: 2021-06-2
Quantifying progress across different CMIP phases with the ESMValTool
No full textMore than 40 model groups worldwide are participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6), providing a new and rich source of information to better understand past, present, and future climate change. Here, we use the Earth System Model Evaluation Tool (ESMValTool) to assess the performance of the CMIP6 ensemble compared to the previous generations CMIP3 and CMIP5. While CMIP5 models did not capture the observed pause in the increase in global mean surface temperature between 1998 and 2013, the historical CMIP6 simulations agree well with the observed recent temperature increase, but some models have difficulties in reproducing the observed global mean surface temperature record of the second half of the 20th century. While systematic biases in annual mean surface temperature and precipitation remain in the CMIP6 multi-model mean, individual models and high-resolution versions of the models show significant reductions in many long-standing biases. Some improvements are also found in the vertical temperature, water vapor and zonal wind speed distributions, and root mean square errors for selected fields are generally smaller with reduced inter-model spread and higher average skill in the correlation patterns relative to observations. An emerging property of the CMIP6 ensemble is a higher effective climate sensitivity with an increased range between 2.3 and 5.6 K. A possible reason for this increase in some models is improvements in cloud representation resulting in stronger shortwave cloud feedbacks than in their predecessor versions
SELF- AND AIR-BROADENED LINE SHAPE PARAMETERS OF 12CH4 : 4500-4620 CM−1
No full textAccurate knowledge of spectral line shape parameters is important for infrared transmission
and radiance calculations in the terrestrial atmosphere. We report the
self- and air-broadened Lorentz widths, shifts and line mixing coefficients
along with their temperature dependences for methane absorption lines in the 2.2 m
spectral region. For this, we obtained a series of high-resolution,
high S/N spectra of 99.99 C-enriched samples of pure methane and its
dilute mixtures in dry air
at cold temperatures down to 150 K using the Bruker IFS 125HR Fourier transform
spectrometer at JPL. The coolable absorption cell had an optical path of 20.38 cm and
was specially built to reside inside the sample compartment of the Bruker
FTS\footnote{K.~Sung, A.~W.~Mantz, L.~R.~Brown, \textit{et al.}, \textit{J. Mol. Spectrosc.}
\underline{\textbf{162}} (2010) 124-134.}. The 13 spectra used in the analysis consisted
of seven pure CH spectra at pressures from 4.5 to 169 Torr
and six air-broadened
spectra with total sample pressures of 113-300 Torr and methane volume mixing ratios
between 4 and 9.7. These 13 spectra were fit simultaneously using the
multispectrum least-squares fitting technique\footnote{D.~C.~Benner,
C.~P.~Rinsland, V.~Malathy Devi, M.~A.~H.~Smith and
D.~Atkins, \textit{JQSRT} \underline{\textbf{53}} (1995) 705-721.}. The results
will be compared to existing values reported in the literature.\footnote{Research described
in this paper was performed at Connecticut College, the College of William and Mary,
NASA Langley Research Center and the Jet Propulsion Laboratory, California
Institute of Technology, under contracts and cooperative agreements with the National
Aeronautics and Space Administration.}Made available in DSpace on 2014-09-17T16:55:06Z (GMT). No. of bitstreams: 3
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Previous issue date: 2014-06-1
Using dimers to measure biosignatures and atmospheric pressure for terrestrial exoplanets
No full textWe present a new method to probe atmospheric pressure on Earth-like planets using (O-O) dimers in the near-infrared. We also show that dimer features could be the most readily detectable biosignatures for Earth-like atmospheres and may even be detectable in transit transmission with the James Webb Space Telescope (JWST). The absorption by dimers changes more rapidly with pressure and density than that of monomers and can therefore provide additional information about atmospheric pressures. By comparing the absorption strengths of rotational and vibrational features to the absorption strengths of dimer features, we show that in some cases it may be possible to estimate the pressure at the reflecting surface of a planet. This method is demonstrated by using the O A band and the 1.06 μm dimer feature, either in transmission or reflected spectra. It works best for planets around M dwarfs with atmospheric pressures between 0.1 and 10 bar and for O volume mixing ratios above 50% of Earth's present-day level. Furthermore, unlike observations of Rayleigh scattering, this method can be used at wavelengths longer than 0.6 μm and is therefore potentially applicable, although challenging, to near-term planet characterization missions such as JWST. We also performed detectability studies for JWST transit transmission spectroscopy and found that the 1.06 and 1.27 μm dimer features could be detectable (SNR>3) for an Earth analogue orbiting an M5V star at a distance of 5 pc. The detection of these features could provide a constraint on the atmospheric pressure of an exoplanet and serve as biosignatures for oxygenic photosynthesis. We calculated the required signal-to-noise ratios to detect and characterize O monomer and dimer features in direct imaging-reflected spectra and found that signal-to-noise ratios greater than 10 at a spectral resolving power of R=100 would be required.Peer reviewe
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