Volume 122, Issue 22, 08 June 2005
Index of content:
122(2005); http://dx.doi.org/10.1063/1.1928228View Description Hide Description
The unimolecular dissociation of is investigated by exciting the molecule in the region of its band and probing the resulting OH fragments using laser-induced fluorescence. The measured OH fragment rotational and translational energies are used to determine the bond dissociation energy, which we estimate to be . Combining this value with the known heats of formation of the fragments also gives an estimate for the heat of formation of which at we determine to be . This experimental value is in good agreement with the results of ab initio calculations carried out at the CCSD(T)/complete basis set limit which finds the heat of formation of at to be .
122(2005); http://dx.doi.org/10.1063/1.1935515View Description Hide Description
The hydrogen and water molecules are ubiquitous in the Universe. Their mutual collisions drive watermasers and other line emission in various astronomical environments, notably molecular clouds and star-forming regions. We report here a full nine-dimensional interaction potential for calibrated using high-accuracy, explicitly correlated wave functions. All degrees of freedom are included using a systematic procedure transferable to other small molecules of astrophysical or atmospherical relevance. As a first application, we present rate constants for the vibrational relaxation of the bending mode of obtained from quasiclassical trajectory calculations in the temperature range of 500–4000 K. Our high-temperature results are found compatible with the single experimental value at 295 K. Our rates are also significantly larger than those currently used in the astrophysical literature and will lead to a thorough reinterpretation of vibrationally excited wateremission spectra from space.