Molecular vibration excitation

Coherent control of molecular vibrational excitation and subsequent dissociation [1] ... 

In the case of vibrational excitation of NH3 at a metal surface a very different dependence has been observed [119]. In this case, the vibrational excitation could be attributed to mechanical excitation of the NH3 umbrella mode in the collision with the surface. Finally, it is worth mentioning that at much higher energies, way into the domain of tens of eV s, mechanical excitation will lead to molecular vibrational excitation and dissociation for all molecules, see e.g. [120]. 

The next natural step is the discussion of Fermi resonance effects in molecular crystals. Let molecules having Fermi resonance between intramolecular vibrations form a molecular crystal due to weak (van der Waals) forces. Then the individual molecular vibrational excitations discussed above become coupled to each other and form collective Fermi resonance bands. We shall consider here a simple two-layer ID model with intermolecular interaction only between nearest neighbors (see Fig. 9.6). 

Quasi-elastic neutron scattering (QENS) is related to stochastic particle motions. Because the displacements are random, the diffusive motion of particles in liquids caimot be quantized, and the energies are continuously distributed. Unlike the case of cooperative motions like phonons in solids or molecular vibrational excitations, in the dynamic scattering function S(Q,(o), there are no 5-functions at finite momentum and energy transfers. Instead, the dynamic scattering function is centered at zero-energy transfer with a characteristic quasielastic line width proportional to the diffusivity of the particles. 

On the basis of the dressed photon theory and the important role of electric dipole-forbidden molecular vibrational excitations, recent theoretical studies have proposed a simple model to describe atom or atom-cluster desorption due to the dressed photons from a nanometric particle deposited on a substrate [49]. Assuming an anharmonic potential for each atomic binding, an effective atom-nanodot potential was evaluated to determine the desorption energy and the stabilized dot size. The model shows that electric dipole-forbidden molecular vibrational excitations play an important role in the phonon-assisted process, which could potentially lead to a novel fabrication method, in addition to controlling the size and position of nanostructures [51]. 

Unstable species such as O, FI and N atoms, molecular radicals and vibrationally excited diatomics can be injected by passmg the appropriate gas tluough a microwave discharge. In a SIFT, the chemistry is usually straightforward since there is only one reactant ion and one neutral present in the flow tube. 

Conventional spontaneous Raman scattering is the oldest and most widely used of the Raman based spectroscopic methods. It has served as a standard teclmique for the study of molecular vibrational and rotational levels in gases, and for both intra- and inter-molecular excitations in liquids and solids. (For example, a high resolution study of the vibrons and phonons at low temperatures in crystalline benzene has just appeared [38].)... 

EELS Electron energy loss spectroscopy The loss of energy of low-energy electrons due to excitation of lattice vibrations. Molecular vibrations, reaction mechanism... 

Vaccaro P H 1995 Resonant four-wave mixing spectroscopy a new probe for vibrationally-excited species Molecular Dynamics and Spectroscopy by Stimulated Emission Pumping (Advances in Chemistry Series) vol 7, ed H-L Dai and R W Field (Singapore World Scientific) p 1... 

A) During the luultiphoton excitation of molecular vibrations witli IR lasers, many (typically 10-50) photons are absorbed in a quasi-resonant stepwise process until the absorbed energy is suflFicient to initiate a unimolecular reaction, dissociation, or isomerization, usually in the electronic ground state. 

The photoelectron spectrum of nitrogen (N2) has several peaks, a pattern indicating that electrons can be found in several energy levels in the molecule. Each main group of lines corresponds to the energy of a molecular orbital. The additional "fine structure" on some of the groups of lines is due to the excitation of molecular vibration when an electron is expelled. 

When an excited state is converted by ejection of an atomic electron, a high positive charge can be produced through subsequent Auger electron emission. Within the period of molecular vibration this charge is spread throughout the molecule to all atoms, and a Coulomb explosion results. This primary phenomenon occurs, of course, not only as a result of [ decay, but must be taken into account in all cases of nuclear reaction when deexcitation by inner electron conversion occurs... 

The use of supercomputers has allowed us to test the sensitivity of accurate quantal molecular energy transfer probabilities in diatom-diatom collisions to the choice of potential energy surface, even at total energies great enough to allow both diatoms to be vibrationally excited. 

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