Abstract book - Prof. Per Jensen, Ph.D. - Bergische Universität ...

194 Poster session, J31Joint Ro-Vibrational Analysis of Vibrational States of CH 2 D 2up to 9000 cm -1 and “Experimental” Determination of r e and InternalForce Field Methane ParametersO. N. Ulenikov 1, 2 , E. S. Bekhtereva 1, 2 , S. Albert 1 , H. Hollenstein 1 and M. Quack 11 Physical Chemistry Laboratory, ETH-Zürich, CH-8093, Zürich, Switzerland; 2 TomskState University, Physics Department, 634050, Tomsk, RussiaUlenikov O.N.Bekhtereva E.S.Albert S.Hollenstein H.Quack M.Methane is an important prototype for intramolecular dynamics 1 and of relevance in avariety of spectroscopic contexts. We report here results of the first joint rovibrationalanalysis of a set of vibrational bands located below 9000 cm -1 . The number ofvibrational states included is about 550; ro-vibrational structures were quantum stateresolved and assigned for 114 vibrational levels. 2 The other bands are considered as”dark”.The ro-vibrational analysis was made on the basis of the”Global Fit” method. 3 Allspectroscopic parameters (band centers, rotational and centrifugal distortion parameters,different kinds of both the Fermi- and Coriolis-type parameters) were expressed asfunctions of more fundamental properties of the molecule. Ideally, we can describe therotational structure of all vibrational states of the ground electronic state of CH 2 D 2 . Useof operator perturbation theory allowed us to express many of the ”more fundamentalparameters” as functions of the equilibrium CH bond length, r e , and other parameters ofthe methane intramolecular potential function, F i..j .The main advantages of our model are (1) the possibility of joint consideration of alarge number of vibrational states, (2) the possibility to correctly take into account”dark” states, and (3) a considerable reduction of the number of free (fitted) parametersin comparison with the traditional effective Hamiltonian model.In particular, in our study we were able to reproduce about 6000 ro-vibrational energies(more than 17000 line positions) of the 114 vibrational states (d rms better than 0.02 cm -1 )with less than 350 fitted parameters. The r e value, cubic and some of the quartic forcefield parameters of the methane were obtained as well.References[1] R. Marquardt and M. Quack, J. Chem. Phys., 109, 10628-10643, 1998.J. Phys. Chem., A 108, 3166-3181, 2004, (and references cited therein);and in Handbook of High Resolution Spectroscopy, M. Quack and F. Merkt eds.,Wiley, Chichester 2011.[2] O. N. Ulenikov, E. S. Bekhtereva, S. Albert, S. Bauerecker, H. Hollenstein,and M. Quack, J. Phys. Chem., A 113, 2218-2231, 2009.[3] O. N. Ulenikov, A.-W. Liu, E. S. Bekhtereva, G. A. Onopenko, O. V. Gromova, L.Wan, S.-M. Hu, and J.-M. Flaud, J. Mol. Spectrosc., 240, 32-44, 2006.