1. Theoretical work on the water monomer and dimer Matt Barber Jonathan Tennyson University College London matt@theory.phys.ucl.ac.uk September 2009

2. Monomer line list Extended to cover 800-20000 cm -1 Now uses HITRAN 2008  The HITRAN 2008 molecular spectroscopic database Rothman, LS; Gordon, IE; Barbe, A, et al. JQSRT 110/9-10 pp533-572, 2009 Includes calculated line profile data IUPAC group: Recommends not using Voigt profiles – introduce speed-dependent widths

3. Band intensities Look at purely vibrational structure, ignoring rotation. Can be calculated from line lists HITRAN, BT2, etc. Model using dipole and potential surface. Calculate by allowing “forbidden” J=0 to 0 transition. Effects of dimer structure for changes in intensities and shifts of band origins.

4. Experimental Band intensities Need to go back to HITRAN 92  Not a particularly useful model  Superceded by rovibrational modelling However, can be calculated from newer databases Makes a useful benchmark for ab initio models

5. Ab initio calculations DVR software suite  Go back to 1992 version for DIPJ0 program  Requires transformation to Eckart co-ordinates Start with monomer Potential energy surface  Spectroscopically determined potential energy surfaces of the (H2O)-O-16, (H2O)- O-17, and (H2O)-O-18 isotopologues of water Shirin, SV; Polyansky, OL; Zobov, NF, et al. JOURNAL OF MOLECULAR SPECTROSCOPY 236/2, 2006 CVR Dipole surface  A new ab initio ground-state dipole moment surface for the water molecule, Lodi, L; Tolchenov, RN; Tennyson, J, et al. JOURNAL OF CHEMICAL PHYSICS 128/4, 2008

7. Moving to the Dimer New dimer dipole surface One molecule in ground state, the other in excited state Large r (100 a.u.) to compare with monomer Apply correction from monomer Move to equilibrium configuration  (and others in due course)

11. Band intensities to spectra Band origins  From Ross’s work Band profiles  Good approximation at low T  More work needed at room temperature What resolution is required?

13. Future plans Adapt wavefunctions by adjusting the potential surface Extend spectral region  Greater than 10000 cm -1 requires more computation, but possible Regions for more careful analysis?