High sensitivity ICLAS of H218O in the 12,580-13,550 cm-1 transparency window

High-sensitivity Intracavity Laser Absorption Spectroscopy (ICLAS) is used to measure the high resolution absorption spectrum of (H2O)-O-18 between 12,580 and 13,550 cm(-1). This spectral region covers the 3 nu+delta polyad of very weak absorption. Four isotopologues of water ((H2O)-O-18, (H2O)-O-16, (H2O)-O-17, (HDO)-O-18) are found to contribute to the observed spectrum. Spectrum analysis is performed with the aid of variational calculations and allowed for assigning 1126 lines belonging to (H2O)-O-18, while only 160 (H2O)-O-18 lines are included in the HITRAN-2008 database. Altogether, 823 accurate energy levels of (H2O)-O-18 are determined from transitions attributed to 26 upper vibrational states, 438 of them being reported for the first time. New information includes energy levels of four newly observed vibrational states of (H2O)-O-18: (2 4 0),(1 4 1), (0 4 2) and (2 3 1) at 13,167.718,13,212.678, 13,403.71 and 15,073.975 cm(-1), (H2O)-O-18 transitions involving highly excited bending states like (1 6 0), (0 6 1), (0 7 1),(1 7 0),(09 0) and even (0 10 0) have been identified as a result of an intensity borrowing from stronger bands via high-order resonance interactions. Thirty-six new energy levels of (H2O)-O-17, present with a 2% relative concentration in our sample, could be determined. The rotational structure of the (0 2 3) state of (HDO)-O-18 at 13,245.497 cm(-1) is also reported for the first time. (C) 2010 Elsevier Ltd. All rights reserved.