IMPROVED FAR-INFRARED AMMONIA INTENSITY FROM EMPIRICAL HAMILTONIAN MODEL

In the 2016 meeting we reported our experimental linelist of NH$_3$ in 50-660 cm$^{-1}$ (See Paper FE08). The retrieved line positions and intensities were used as standards to validate HITRAN 2012 database and our empirical Hamiltonian models (Yu et al. 2010; Pearson et al. 2016). While the line position comparisons with HITRAN and our Hamiltonian models were excellent, the intensity comparisons were less satisfactory. During the past two years, we have updated our Hamiltonian model to improve the intensity prediction. In this presentation, we will report our significant improvement on intensity predictions, especially for the $\Delta K=$3 forbidden transitions. We will also report comparisons of HITRAN 2016 with our existing experimental spectra

FT-IR MEASUREMENTS OF O2 COLLISION-INDUCED ABSORPTION IN THE 565 – 700 NM REGION USING A HIGH PRESSURE GAS ABSORPTION CELL

The collision-induced absorptions (CIA) of O$_2$ and dry air were measured in the near-infrared and visible region, covering the O$_2$ B-band at 687 nm and double transitions in the 630 and 577 nm region. A newly customized 1 m pathlength high-pressure cell was developed and configured to a Fourier transform spectrometer, Bruker 125HR, at the Jet Propulsion Laboratory. A super luminous cutting-edge Laser-Driven Light Source (LDLS), was also used to improve the photon flux offered by the spectrometer. A series of spectra of pure O$_2$ and dry air were obtained at various pressures up to 131 bars at room temperature. For the CIA of O2 B-band region, the monomer resonance absorption contribution to the observed spectra has been subtracted by simulating their absorption with a speed-dependent Voigt line shape profile with line mixing effects taken into account. The remaining absorption component was interpreted as the CIA component in the region. The integrated absorption coefficient was measured to be 0.024(6)$\times$10$^{-4}$ cm$^{-1}$/Amag$^2$ for the O$_2$ B-band region, which are significantly lower than early measurements. For the two double transition bands in the 630 and 577 nm regions, however, the integrated CIA from this work were measured to be 2.50(14) and 3.17(18)$\times$10$^{-4}$ cm$^{-2}$/Amag$^2$, respectively, which are significantly higher than their corresponding early measurements. For dry air, the integrated CIA were measured to be 0.10(2) and 0.15(2)$\times$10$^{-4}$ cm$^{-2}$/Amag$^2$, respectively, for the 630 and 577 nm region, with no appreciable contribution from the O$_2$-N$_2$ pairs in this work. The results are compiled in electronic supplements.$^\&$ $^\&$ Government sponsorship acknowledged

FT-IR measurements of NH3 line intensities in the 60 – 550 CM−1 using Soleil/Ailes beamline

Ammonia (NH$_3$) has been found ubiquitous, $it{e.g.}$, in the interstellar medium, low-mass stars, Jovian planets of our solar system, and possibly in the low temperature exoplanets. Their spectroscopic line parameters are essential in the accurate interpretation of the planetary and astrophysical spectra observed with Herschel, SOFIA, ALMA, and JWST. In our previous paperfootnote{S. Yu, et al. J. Chem. Phys. (2010) 174317/1-174317/14.}, the NH$_3$ line positions in the far-IR region were studied for the ground state and $nu_2$ in an unprecedented accuracy, which revealed significant deficiencies in the NH$_3$ intensities, for instance, some weak $Delta$K = 3 lines were predicted to be ~100 times stronger. Measurement of line intensity for these lines in a consistent manner is demanded because the $Delta$K = 3 forbidden lines are only way other than collisions and $l$-doubled states to excite NH$_3$ to $K > 0$ levels. Recalling that NH$_3$ transition lines in the high $J$ and $K$ up to 18 were detected toward the galactic center in the star forming region of Sgr B$_2$, their accurate intensity measurements are critical in explaining the observed high $K$ excitation, which will provide insights into radiative-transfer $it{vs.}$ collision excitation mechanics of interstellar NH$_3$. For this, we obtained a series of spectra of $^{14}$NH$_3$ in the 50 � 550 cm$^{-1}$ using a Fourier-transform spectrometer, Bruker 125HR, and AILES beam line at Synchrotron SOLEIL, France. Line positions, intensities, and pressure-broadened half-widths have been measured using non-linear least squares spectrum fitting algorithm. In this presentation we report and discuss preliminary results of line position and intensity measurements for the inversion transitions in the ground state, $nu_2$, 2$nu_2$, $nu_4$ and for the vibration-rotation transitions of $nu_2$, 2$nu_2$, $nu_4$, 2$nu_2-nu_2$, $nu_4-nu_2$ and $nu_4-2nu_2$ in this region. Comparison of the new measurements with the current databases and {it ab initio} calculations will be discussed

MEASUREMENT AND MODELING OF COLD 13CH4 SPECTRA FROM 2.1 TO 2.7 _m

A new study of $^{13}$chem{CH_4}line positions and intensities in the Octad region between 3600 and 4800 wn will be reported. Nine spectra were recorded with two Fourier transform spectrometers (the McMath-Pierce FTS at Kitt Peak Observatory and the Bruker 125 HR FTS at the Jet Propulsion Laboratory) using $^{13}$C-enriched samples at temperatures from 299 K to 80 K. Line positions and intensities were retrieved by non-linear least squares curve-fitting procedures and analyzed using the effective Hamiltonian and the effective Dipole moment expressed in terms of irreducible tensor operators adapted to spherical top molecules. Quantum assignments were found for all the 24 sub-vibrational states of the Octad (some as high as J=10). Over 4750 experimental line positions and 3300 line intensities were fitted with RMS standard deviations of 0.004 wn and 6.9%, respectively. A new linelist of over 9600 measured positions and intensities from 3607 to 4735 wn was produced, with known quantum assignments given for 45% of the features.$^{a}$ $^{a}$ Part of the research described in this paper was performed at the Jet Propulsion Laboratory, California Institute of Technology, NASA Langley Research Center, and Connecticut College, under contracts and cooperative agreements with the National Aeronautics and Space Administration. The support of the Groupement de Recherche International SAMIA between CNRS (France) and RFBR (Russia) is acknowledged

FT-IR MEASUREMENTS OF COLLISION-INDUCED ABSORPTION OF O2(A) BAND USING A HIGH-PRESSURE GAS ABSORPTION CELL

In support of the precision atmospheric remote sensing (e.g., OCO-2, GOSAT missions), the collision-induced absorptions (CIA) of O2-O2, O2-Air, and O2-H2O have been measured in the O2(A) band region centered at 760 nm. For this, a newly developed 1 m pathlength high-pressure cell (rated up to 150 bars at an operating temperature of 315 Celcius) was configured to a Fourier transform spectrometer, Bruker 125HR, at the Jet Propulsion Laboratory, along with a super-luminant Laser-Driven Light Source (LDLS). A series of spectra of pure O2 and dry air were obtained at various pressures up to 116 bars at room temperature. For the O2-H2O CIA measurement, we collected the spectra at elevated temperatures, 500 K, to secure sufficiently high pressure of water vapor. The CIA of the O2 A-band was derived from multiple spectra in two steps; (i) First, their monomer absorptions have been simulated by using a speed-dependent Voigt line shape profile at the experimental conditions of individual observed spectra. The line mixing effects have been taken into account through both the Rosenkranz first-order approximation and the full-line mixing matrix operation, respectively. (ii) The simulated monomer absorption contribution has been subtracted from their corresponding observed spectra. The remaining absorption component was interpreted as the CIA component in the region. The results will be presented for O2-O2 and O2-Air, respectively, at the room temperatures along with the comparison with the existing data sets and discussion. The O2(A) band CIA by hot water will also be presented at 500 K for the first time

14NH3 line positions and intensities in the far-infrared: comparison of FT-IR measurements to empirical hamiltonian model predictions

We have analyzed multiple spectra of high purity (99.5\%) normal ammonia sample recorded at room temperatures using the FT-IR and AILES beamline at Synchrotron SOLEIL, France. More than 2830 line positions and intensities are measured for the inversion-rotation and rovibrational transitions in the 50 – 660 \wn region. Quantum assignments were made for 2047 transitions from eight bands including four inversion-rotation bands (gs(a-s), \nub{2}(a-s), 2\nub{2}(a-s), and \nub{4}(a-s)) and four ro-vibrational bands (\nub{2} – gs, 2\nub{2} – gs, \nub{4} – \nub{2}, and 2\nub{2} –\nub{4}), as well as covering more than 300 lines of $\Delta$K = 3 forbidden transitions. Out of the eight bands, we note that 2\nub{2} – \nub{4} has not been listed in the HITRAN 2012 database. The measured line positions for the assigned transitions are in an excellent agreement (typically better than 0.001 \wn) with the predictions from the empirical Hamiltonian model [S. Yu, J.C. Pearson, B.J. Drouin, et al.(2010)] in a wide range of J and K for all the eight bands. The comparison with the HITRAN 2012 database is also satisfactory, although systematic offsets are seen for transitions with high J and K and those from weak bands. However, differences of 20\% or so are seen in line intensities for allowed transitions between the measurements and the model predictions, depending on the bands. We have also noticed that most of the intensity outliers in the Hamiltonian model predictions belong to transitions from gs(a-s) band. We present the final results of the FT-IR measurements of line positions and intensities, and their comparisons to the model predictions and the HITRAN 2012 database.\footnote {Research described in this paper was performed at the Jet Propulsion Laboratory and California Institute of Technology, under contracts and cooperative agreements with the National Aeronautics and Space Administration.

FT-IR measurements of mid-IR propene (C3H6) cross sections for titan stratosphere

We present temperature dependent cross sections of propene (C$_3$H$_6$CH$_2$-CH-CH$_3$, propylene), which was detected in the stratosphere of Titan.\footnote{C. A. Nixon, et al., Astrophys. J. Lett., 776, L14 (2013).} For this study, a series of high-resolution (0.0022 \wn) spectra of pure and N$_2$-mixture samples were recorded at 150 – 296 K in the 650 – 1530 \wn (6.5 – 15.3 $\mu$m) at the Jet Propulsion Laboratory using a Fourier-transform spectrometer and a custom-designed cold cell\footnote{A.W. Mantz, K. Sung, et al. 65th Symposium on Molecular Spectroscopy, Columbus, OH, 2010.}\footnote{K. Sung, A.W. Mantz, et al., J. Mol. Spectrosc. 262, 122 – 134 (2010).}. The observed spectral features cover the strongest band (\nub{19}) with its outstanding Q-branch peak at 912 \wn and three other strong bands: \nub{18}, \nub{16} and \nub{7} at 990, 1442, and 1459 \wn, respectively. In addition, we have generated a HITRAN-format empirical ‘pseudoline list' consisting of line positions, intensities, and effective lower state energies, which were determined by fitting all the observed propene spectra simultaneously. A newly derived partition function was used in the analysis. The results are compared with early work from relatively warm temperatures (278 – 323 K).\footnote{Research described in this talk was performed at the Jet Propulsion Laboratory, California Institute of Technology, Connecticut College, and NASA Langley Research Center under contracts and cooperative agreements with the National Aeronautics and Space Administration.

PROGRESS ON THE FT-IR MEASUREMENTS OF WATER CONTINUUM IN THE FAR-INFRARED REGION AT 252 – 296 K

\begin{wrapfigure}{r}{0pt} \includegraphics[scale=0.25]{B0157.4b.water-cntm4.eps} \end{wrapfigure} Water is the strongest greenhouse gas in the Earth atmosphere, which plays a critical role in the energy balance of the earth atmosphere. It has long been observed particularly in the far-infrared that there is significant longwave continuum absorption due to water vapor (dimers or multimers), not attributable to the Lorentz line contribution within 25 cm$^{-1}$ from the line center for individual water vapor lines. The MT\_CKD model offers the water vapor continuum predictions, which are to be validated by a laboratory study in the far infrared. In order to directly measure this water vapor continuum absorption, we have obtained a series of spectra of water vapor broadened by Self, N$_2$, and O$_2$ in the 50 – 500 cm$^{-1}$ (200 – 20 $\mu$m) at temperatures between 251 and 296 K. For this, we used a coolable White cell system (whose optics are optimized for the far-infrared spectrometry) with passive temperature control, configured to the Fourier transform spectrometer, Bruker IFS-125HR at the Jet Propulsion Laboratory (JPL). We have been analyzing the spectra to make direct measurement of the far-infrared water continuum in two steps; (1) we obtained their transmission spectra by ratioing the sample spectrum to their corresponding background spectrum, (2) we obtained the continuum part of the transmission by dividing the measured spectrum by a synthetic spectrum of the resonant lines calculated using the HITRAN database. As shown in Figure 1, it has revealed the underlying water-water, water-O$_2$, and water-N$_2$ continua in the temperature range, depending on the spectrum type. The preliminary results from this on-going analysis are presented along with their comparison with the MT\_CKD (ver.3.5) model predictions. Temperature dependence of the water vapor continuum will be discussed as part of future work.\footnote{Government sponsorship acknowledged}

PROGRESS IN THE MEASUREMENT ON TEMPERATURE-DEPENDENCE OF H2-BROADENING OF COLD AND HOT CH4

We report preliminary measurements on the temperature dependence of H$_{2}$-broadening of CH$_{4}$ in the near infrared at temperatures between 100 and 370 K. In support of the Jovian and exoplanet atmospheric remote sensing in the near infrared, we have measured the temperature dependence of H$_{2}$-broadened half width and pressure shift coefficients of CH$_{4}$, both of which are known to be rotational quantum number dependent. We studied both cold and hot CH$_{4}$ in the atmospheric K band (~2.2 $mu$m) with the focus on a) weaker lines in the nub{2}+nub{3} band at low temperatures for cold giant planets and b) stronger lines in the nub{3}+nub{4} band at elevated temperatures for extra-solar planets (e.g., hot-Jupiters). Three custom-built gas absorption cells (two cold and one hot) were used to obtain the spectra of CH$_{4}$ and H$_{2}$ mixtures at temperatures between 100 and 370 K. We will discuss our on-going spectrum analysis for a few select {it J} manifolds and provide comparisons with published values, which are available only at room temperature

Line Parameters including Temperature Dependences of Air- and Self-broadened Line Shapes of (CO2)-C-12-O-16: 2.06-mu m Region

This study reports the results from analyzing a number of high resolution, high signal-to-noise ratio (S/N) spectra in the 2.06-μm spectral region for pure CO2 and mixtures of CO2 in dry air. A multispectrum nonlinear least squares curve fitting technique has been used to retrieve the various spectral line parameters. The dataset includes 27 spectra: ten pure CO2, two 99% 13C-enriched CO2 and fifteen spectra of mixtures of 12C-enriched CO2 in dry air. The spectra were recorded at various gas sample temperatures between 170 and 297 K. The absorption path lengths range from 0.347 to 49 m. The sample pressures for the pure CO2 spectra varied from 1.1 to 594 Torr; for the two 13CO2 spectra the pressures were ∼10 and 146 Torr. For the air-broadened spectra, the pressures of the gas mixtures varied between 200 and 711 Torr with CO2 volume mixing ratios ranging from 0.014% to 0.203%. The multispectrum fitting technique was applied to fit simultaneously all these spectra to retrieve consistent set of line positions, intensities, and line shape parameters including their temperature dependences; for this, the Voigt line shape was modified to include line mixing (via the relaxation matrix formalism) and quadratic speed dependence. The new results are compared to select published values, including recent ab initio calculations. These results are required to retrieve the column averaged dry air mole fraction (XCO2) from space-based observations, such as the Orbiting Carbon Observatory-2 (OCO-2) satellite mission that NASA launched in July 2014