A computed list of H 2 16 O infrared transition frequencies and intensities is presented. The list, BT2, was produced using a discrete variable representation two-step approach for solving the rotation-vibration nuclear motions. It is the most complete water line list in existence, comprising over 500 million transitions (65 per cent more than any other list) and it is also the most accurate (over 90 per cent of all known experimental energy levels are within 0.3 cm −1 of the BT2 values). Its accuracy has been confirmed by extensive testing against astronomical and laboratory data.The line list has been used to identify individual water lines in a variety of objects including comets, sunspots, a brown dwarf and the nova-like object V838 Mon. Comparison of the observed intensities with those generated by BT2 enables water abundances and temperatures to be derived for these objects. The line list can also be used to provide an opacity for models of the atmospheres of M dwarf stars and assign previously unknown water lines in laboratory spectra.

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Ab initio semiglobal potential energy and dipole moment hypersurfaces for the isomerising HCN-HNC system are computed, using a grid of 242 points, principally at the all-electron cc-pCVQZ CCSD͑T͒ level. Several potential energy hypersurfaces ͑PES͒ are presented including one which simultaneously fits 1527 points from earlier ab initio, smaller basis CCSD͑T͒ calculations of Bowman et al. ͓J. Chem. Phys. 99, 308 ͑1993͔͒. The resulting potential is then morphed with 17 aug-cc-pCVQZ CCSD͑T͒ points calculated at HNC geometries to improve the representation of the HNC part of the surface. The PES is further adjusted to coincide with three ab initio points calculated, at the cc-pCV5Z CCSD͑T͒ level, at the critical points of the system. The final PES includes relativistic and adiabatic corrections. Vibrational band origins for HCN and HNC with energy up to 12 400 cm Ϫ1 above the HCN zero-point energy are calculated variationally with the new surfaces. Band transition dipoles for the fundamentals of HCN and HNC, and a few overtone and hot band transitions for HCN have been calculated with the new dipole surface, giving generally very good agreement with experiment. The rotational levels of ground and vibrationally excited states are reproduced to high accuracy.

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The updated 2009 edition of the spectroscopic database GEISA (Gestion et Etude des Informations Spectroscopiques Atmosphé riques; Management and Study of Atmospheric Spectroscopic Information) is described in this paper. GEISA is a computer-accessible system comprising three independent sub-databases devoted, respectively, to: line parameters, infrared and ultraviolet/visible absorption cross-sections, microphysical and optical properties of atmospheric aerosols. In this edition, 50 molecules are involved in the line parameters sub-database, including 111 isotopologues, for a total of 3,807,997 entries, in the spectral range from 10 À 6 to 35,877.031 cm À 1. The successful performances of the new generation of hyperspectral sounders depend ultimately on the accuracy to which the spectroscopic parameters of the optically active atmospheric gases are known, since they constitute an essential input to the forward radiative transfer models that are used to interpret their observations. Currently, GEISA is involved in activities related to the assessment of the capabilities of IASI (Infrared Atmospheric Sounding Interferometer; http://smsc.cnes.fr/IASI/index.htm) on board the METOP European satellite through the GEISA/IASI database derived from GEISA. Since the Metop-A (http://www.eumetsat.int) launch (19 October 2006), GEISA is the reference spectroscopic database for the validation of the level-1 IASI data. Also, GEISA is involved in planetary research, i.e., modeling of Titan's atmosphere, in the comparison with observations performed by Voyager, or by ground-based telescopes, and by the instruments on board the Cassini-Huygens mission. GEISA, continuously developed and maintained at LMD (Laboratoire de Mé té orologie Dynamique, France) since 1976, is implemented on the IPSL/CNRS (France) ''Ether'' Products and Services Centre WEB site (http://ether.ipsl.jussieu.fr), where all archived spectroscopic data can be handled through general and user friendly associated management software facilities. More than 350 researchers are registered for on line use of GEISA.