Vibrational excitation energy, molecular

The loss of vibrational excitation energy by a molecular entity through energy transfer to the environment due to collisions. 

Mazevet, S., Morrison, M.A., Boydstun, O. and Nesbet, R.K. (1999). Inclusion of nonadiabatic effects in calculations on vibrational excitation of molecular hydrogen by low-energy electron impact, Phys. Rev. A 59, 477 189. 

Figure 2.2d shows the simplest type of nondissociative electron capture into discrete states of AB- that will occur between energies E1 and Ei, resulting in a vibrationally excited AB- molecular ion. If the capture process remains an isolated event, the electron will be ejected by autodetachment (Auger process) within a time comparable with a vibration time. 

Molecular fluorescence is caused by irradiation of molecules in solution or in the gas phase. As shown in Figure 6-24a, absorption of radiation promotes the molecules into any of the several vibrational levels associated with the two excited electronic levels. The lifetimes of these excited vibrational states are, however, only on the order of 10" s, which is much smaller than the lifetimes of the excited electronic states (10 s). Therefore, on the average, vibrational relaxation occurs before electronic relaxation. As a consequence, the energy of the emitted radiation is smaller than that of the absorbed by an amount equal to the vibrational excitation energy. For example, for the absorption labeled 3 in Figure 6-24a, the absorbed energy is equal to ( 2 0 + Co), whereas the energy of... 

The mean energy of vibrational excitation of molecular ions can, in principle, be evaluated and the characteristic ion decomposition times estimated using the mass spectral data on electron impact and the statistical theory of decomposition. 

Equation 2.35 shows that the allowed vibrational energies are equally spaced and separated by hv. The amount of the latter is specific to the nuclei and the strength of their coupling. The number v is called the vibrational quantum number. It denotes the amount of vibrational excitation energy in the respective molecular state. 

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. 

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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