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

Contributed Lectures, N2 223Two- dimension study of methanol internal rotation in argon matrix.Gleb G. Pitsevich 1 , George A. Pitsevich 2 .1 Belarusian State University, Belarus, pitsevich@bsu.by; 2 Belarusian State University,Belarus, gapitsevich@gmail.comPitsevich G.G.Pitsevich G.A.As demonstrated by the recent studies 1 , the matrix affects to the height of the internalrotation barriers of methanol isolated in the solid matrix. That is reflected by changes insplitting of the torsional states. This splitting has been considered as one of the possiblemechanisms responsible for the appearance of a multiplet structure of some absorptionbands in low temperature FTIR spectra of CH 3 OH. Since the FTIR spectra show nosigns of overall molecule rotation and at the same time there are bands due to internalrotation, we assumed that the axis of rotation (C-O) is fixed relative to the argon atoms.For estimation of argon matrix effect on internal motion in methanol, the configurationincluding a molecule of methanol and eight argon atoms, initially positioned at thevertices of the cube, was optimized. Then the argon atoms were space-fixed and rotationof methyl and hydroxyl groups with respect to the argon lattice was simulated. In thecase of a methyl group rotation by steps of 20º the hydroxyl group position wasadditionally fixed relative to the matrix, and vice versa. Besides, all other internalparameters of СН 3 ОН were optimized. It was computed 64 points on potentialsurface U U( OH, CH) U( 2 , 2 / 3)3OH k CH n .3We were looking for potential surface in the form:i( k OH 3 n CH ) (1)3U (OH,CH) A3k , ne where nk , 3. Then we introduced the following new coordinates:s ;CH3OHIIt I I I ICH3OHCH3CH3 OH CH3 OHwhere ICH 3, IOH- inertial parameters of CH 3 and hydroxyl groups with respect to C-Obond. Substituting (2) in (1) the potential surface in new coordinates ( U U( s, t)) wasobtained. The Schrodinger equation for st , takes the form:where2 2 C D U ( s, t) E 02 2stI IC D ;2 I ( I I ) 2( I I )OH CH3; Ireduce;reduce CH3 OHWe represented potential function as: U( s, t) US( s) UT ( t) UST ( s, t), whereUS( s) U( s,0); UT ( t) U(0, t); UST ( s, t) U( s, t) U( s,0) U(0, t). So we solve the(3) using this representation for potential energy and perturbation theory methods. Thepositions of torsional energy levels, wave functions and transition probabilities werefound.kn ,CH3OHOH(2)(3)(4)References[1] Y.P. Lee, Y.J. Wu, R.M. Lees, L.H. Xu, J.T. Hougen, Science. 311, 365, 2006