Vibrationally excited molecular

A term in photochemistry and photophysics describing an isoenergetic radiationless transition between two electronic states having different multiphcities. Such a process often results in the formation of a vibrationally excited molecular entity, at the lower electronic state, which then usually deactivates to its lowest vibrational energy level. See also Internal Conversion Fluorescence... 

Internal conversion A photophysical process. Isoenergetic radiationless transition between two electronic states of the same multiplicity. When the transition results in a vibrationally excited molecular entity in the lower electronic state, this usually undergoes deactivation to its lowest vibrational level, provided the final state is not unstable to dissociation. 

Nonlinear Raman scattering spectroscopy is a multiphoton spectroscopy that enables access to vibrationally excited molecular levels. Through nonlinear optical processes, this technique allows us to study rich molecular information which cannot be reached by linear optical method. 

Vibrationally excited species also may give up their energy to a suitable catalytic probe. Morgan et al report calorimetric studies of vibrationally excited molecular nitrogen, and compare the results obtained with those from mass spectrometric investigations. 

After giving an overview and interpretative treatment of a wide variety of metastable systems, this paper treats in somewhat more detail a class of highly vibrationally excited molecular anions which undergo electron ejection at rates determined by the strength of vibration-electronic coupling present in the anion. The findings of theoretical simulations of the electron ejection process as well as the experimental relevance of such temporary anions are discussed. 

E14.11 (b) F is formed when F2 loses an antibonding electron, so we would expect Fj" to have a shorter bond than F2, The difference in equilibrium bond length between the ground state (Fi) and excited state (F, + e ) of the photoionization experiment leads us to expect some vibrational excitation in the upper state. The vertical transition of the photoionization will leave the molecular ion with a stretched bond relative to its equilibrium bond length. A stretched bond means a vibrationally excited molecular ion, hence a stronger transition to a vibrationally excited state than to the vibrational ground state of the cation. 

SURFACE EFFECTS IN VIBRATIONALLY EXCITED MOLECULAR BEAM SCATTERING... 

Because of the low collision rate in the high vacuum environment of a Fourier transform mass spectrometer (FTMS), vibrationally excited molecular ions cool predominantly by IR fluorescence. For typical IR transition dipole moments and frequencies in the mid-IR, spontaneous emission is expected to occur at a rate in the range of 1-100 s To energize an ion efficiently using IR multiple-photon excitation (MPE), the rate of photon absorption - the product of absorption cross section and photon flux - should exceed the emission rate. From such a back-of-an-envelope estimate, one finds that radiation sources producing several Watts/cm are required to induce efficient dissociation [141], Note that the demands on laser power may further increase because of the limited residence time of the ions in the laser field, collisional deactivation in traps at higher pressures, limited spectral overlap between molecular absorption and laser emission profiles, etc. 

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