Methane, vibrational modes

The thermochemistry parameters are some of the most useful results of quantum computation. The important features of the overall architecture of a molecule include the connectivity or topology, flexibility, vibration modes and frequencies, shape, moments of inertia, rotational energies and frequencies, and the overall symmetry. The shape of a molecule plays an important part in many of its properties. Some of the most interesting and easy to describe are the long and narrow rod-like eicosane, C20H44, the disk-shaped coronene, C24H12, and the sphere-shaped methane, CH4, adamantine, C10H16, and buckminsterfullerene, C6o-... 

Figures (a) Raman spectra with corresponding photomicrographs and (b) pressure dependence of Raman frequency shifts for the C-H symmetric stretching vibration mode of methane hydrate at 296 K. Crystals in photomicrographs are methane hydrate and surroundings are water at 0.12 GPa, 0.94 GPa, and 1.36 GPa and ice-VI at 1.83 GPa.

Because shells are principally determined by the central ion it is possible to utilize the almost one-to-one ion-ligand relation to reveal the properties of the core ion through studies of the properties of attached molecules [61]. Examples include the IR spectra of CH3 (H2)n cations that have been applied to the study of the structure of protonated methane. The frequencies of the CHs core are sensitive to a number of hydrogen molecules coordinated to this cation. The different possibilities for the occupation of shells are visible as complications in the observed infra-read bands. The statistical occupation of shells, due to many energetically possible isomers, leads to broad and complicated bands. TTie stretching modes of the H2 ligand clearly display the shell structure of complexes. Both experimental and theoretical IR frequencies (Table 5) indicate the well separated vibration modes [45,61]. 

Methane molecules do not possess a permanent dipole moment, and also the quadrupole moment is zero. CH4 exhibits four fundamental vibration modes, the modes Vj and V2, which are in the gas phase IR-forbidden and only Raman-allowed, and the IR- and Raman-active V3 and V4 modes. The corresponding wavenumbers are Vi,V2> 3 and V4,i.e., 2914,1526,3020 and 1306 cm respectively. In fact, V2 of adsorbed CH4 was never observed, most probably because the intensity is too low. The spectra after adsorption on Na-A shown in Fig. 40 were taken at 203-273 K (cf. [216,642). 

As a first demonstration of the FT-Raman technique we present experimental data on the Q-branch of the vj-vibrational mode of methane. Using the supersonic expansion the temperature of CH is effectively lowered leading to a reduced number and width of lines in the Q-band. In pur measurements a 1 2 mixture of CH4 with argon buffer gas was expanded at approximate ... 

Beck R, Maroni P, Papageorgopoulos DC, Dang TT, Schmid MP, Rizzo TR (2003) Vibrational mode-spedflc reaction of methane on a nickel surface. Science 302 98-100... 

We will also discuss first progress in the quantum dynamical treatment of polyatomic molecules (methane) reacting on surfaces, which has come possible, thanks to the development of reduced dimensionality models treating at least one vibrational mode of the molecule, and modeling the surface motion. 

Nave S, Jackson B (2010) Vibrational mode-selective chemistry Methane dissociation on Ni(lOO). Phys Rev B 81 233408... 

Methane, CH4, has only two IR-active vibrational modes. Comment on the expected number of IR-active vibrational modes of CH3D, where one hydrogen atom is replaced by a deuterium. 

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