Collisions of the first kind

The Montroll-Shuler equation can also predict how fast a molecule which is created in a highly excited vibrational state will decay to the equilibrium state. This is of interest in connection with chemiluminescence phenomena. In certain cases one finds experimentally that this relaxation is much faster than what one would expect from the master equation of Montroll and Shuler and improved versions of this equation. One possible mechanism for this fast relaxation is that although most of the collisions in which the diatomic molecule participates are between the diatomic molecule and an inert gas atom, there will also be some collisions between diatomic molecules. In the latter case we have the situation where two diatomic molecules in quantum state n collide producing, with fairly high probability, molecules in quantum states n I and n + 1, respectively. The number of such collisions is, of course quite small compared to the number of collisions of the first kind, but since they are so extremely efficient they may still be of importance. This mechanism, we believe, was first suggested in connection with chemiluminescence by Norrish in a Faraday Society discussion.5 The equations describing this relaxation had, however, been discussed several years earlier by Shuler6 and Osipov.7... 

Collisions where atoms are excited to a higher level by collision with energetic neutrals (collisions of the first kind)... 

Thus each process is in equilibrium with the inverse process and the Boltzmann distribution of each state is maintained by collisions of the first and the second kind, including the ones with electrons, and there are no losses of energy through the emission of radiation or any absorption of radiation from an external source. 

In both cases, large amounts of heat are liberated at the early stages of the spUl. Examples of the first kind of spill are a capsized barge with all the hatches wide open and a gradual leak from a ship in a collision underwater. The second kind involves a spill of fuming sulfuric acid or oleum over water surfaces and shallow surface water. The heat released as a result... 

I here are four sources of line broadening (I) (he uncertainty eCfecl> (2) the Doppler effect. (. ) pressure effects due to collisions between atoms of the same kind and with foreign atoms, and (4) electric and magnetic field effects. We consider only the first three of these phenomena here. The magnetic field effect will be discussed in Section 9C -I in connection with the /eeman effect. 

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