Collision-induced decay

Overall Collision-Induced Decay Rate, k. Expressed in Units of 10 s torr and as Probability per Hard Sphere Collision (parentheses)... 

The investigation of fast processes, such as electron motions in atoms or molecules, radiative or collision-induced decays of excited levels, isomerization of excited molecules, or the relaxation of an optically pumped system toward thermal equilibrium, opens the way to study in detail the dynamic properties of excited atoms and molecules. A thorough knowledge of dynamical processes is of fundamental importance for many branches of physics, chemistry, or biology. Examples are predissociation rates of excited molecules, femtosecond chemistry, or the understanding of the visual process and its different steps from the photoexcitation ofrhodopsin molecules in the retina cells to the arrival of electrical nerve pulses in the brain. 

There are, however, two relaxation processes that prevent the original state, as prepared just after the first 7r/2-pulse ait = 0, from being completely reestablished at the echo time t = 2T. Because of spontaneous or collision-induced decay, the... 

The quantum yield of fluorescence is about 0.18 so that about 80% of the relaxation from the thermal vibrational levels is by nonradiative channels. Evidence in this section indicates that at least most of that nonradiative relaxation is intersystem crossing to the triplet state. The quantum yield of triplet formation is about 0.7, and within the uncertainties of the data, this combined with the small but finite collision-induced decay may account for all nonradiative decay. Triplet formation also occurs in CgDe, and the data again suggest that it may account for essentially all of the nonradiative decay. 

Fig. 2.16. Fluorescence- and collision-induced decay channels of an excited level /)...

The lithium-controlled hierarchical assanbly of the helicates, the monomer-dimer equilibrium, and the dynamic processes can be investigated as crystals or in solution. Gas phase studies can be performed by electrospray ionization mass spectrometry (ESI MS). The measurements help explain the solution behaviors of the compounds. However, gas phase reactivity can be studied as well by collision-induced decay (CID) experiments. ESI MS revealed the following findings. 

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