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\section{IV-4. Towards New Line List of Magnetic Dipole and Electric Quadrupole Transitions in the $a^{1}\Delta_{g}$$\leftarrow$$X^{3}\Sigma^{-}_{g}$ Band of Oxygen}

\textbf{\underline{I.~E.~Gordon},$^a$ L.~S.~Rothman,$^a$ S.~Kassi,$^b$ A.~Campargue,$^b$ G.~C.~Toon$^c$}
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$^a$\textit{Harvard-Smithsonian Center for Astrophysics, Atomic and Molecular
Physics Division, Cambridge MA 02138-1516, USA}

$^b$\textit{Universit\'{e} Joseph Fourier/CNRS, Laboratoire de Spectrom\'{e}trie Physique, 38402 Saint Martin d'H\`{e}res, FRANCE}

$^c$\textit{Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA}
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The spectroscopic parameters for the $a^{1}\Delta_{g}$$\leftarrow$$X^{3}\Sigma^{-}_{g}$ band of molecular oxygen near 1.27 $\mu$m were given in HITRAN almost since the inception of the database. This band is of fundamental importance in the field of remote sensing. Although, the spectral parameters were updated several times numerous uncertainties have remained. Even the most recent update (November, 2009), that was proven to be superior to previous versions of HITRAN in the atmospheric retrievals \footnote{Washenfelder RA, Toon GC, Blavier J-F, Yang Z, Allen NT, Wennberg PO, et al. Carbon dioxide column abundances at the Wisconsin Tall Tower site. J Geophys Res D 2006;111:22305.}, leaves room for improvement. This includes not only correction of the existing parameters (for instance the J-dependence of line intensities for $^{16}$O$^{18}$O) but also accounting for electric quadrupole transitions. The addition of the $\Delta$$J$=$\pm$2 electric quadrupole transitions was recently shown to be important \footnote{Gordon IE, Kassi S, Campargue A, Toon GC. First identification of the electric quadrupole transitions of oxygen in the solar and laboratory spectra. JQSRT 2010;111:1174–-1183.}. Also one has to evaluate, the correlation between the overlapping $\Delta$$J$=$\pm$1, 0 magnetic dipole and electric quadrupole lines. The (1-1) band of $^{16}$O$_{2}$ and (0-0) band of $^{16}$O$^{17}$O have intensities similar to quadrupole transitions, and therefore the reference spectroscopic data for these species is required. In order to provide accurate input parameters for calculation of line lists the CW-Cavity Ring Down Spectroscopy (CW-CRDS) technique has been used to record the high sensitivity absorption spectrum of this band. The spectra were obtained between 7640 and 7917 cm$^{-1}$ with ``natural'' oxygen and the absolute intensities of 377  oxygen transitions were measured. They include the $a^{1}\Delta_{g}$$\leftarrow$$X^{3}\Sigma^{-}_{g}$ (0-0) bands of $^{16}$O$_{2}$, $^{16}$O$^{18}$O and $^{16}$O$^{17}$O. The (0-0) bands of $^{16}$O$_{2}$  contain electric quadrupole transitions with line intensities ranging from 1$\times$10$^{-30}$ to 1.9$\times$10$^{-28}$ cm/molecule. The lines from (1-1) band were also measured.


\index{author}{Kassi S.} \index{author}{Campargue A.} \index{author}{Gordon I. E.} \index{author}{Rothman L. S.} \index{author}{Toon G. C.} 