Krypton, excited, reactions

The equation shows that uranium-235 absorbs a neutron. After absorbing the neutron, the excited uranium nucleus splits and forms barium-141, krypton-92, and three neutrons. Energy is also produced in the reaction. This reaction is only one of a number of different ways that U-235 may split. Several hundred different isotopes have been identified when U-235 undergoes fission. 

The rare gas excimers readily transfer energy to various additives. Rates for transfer to nitrogen and hydrogen in krypton are known at 1 atm. Because excimer species have strong absorptions in the visible region, it is necessary to quench them when studying reactions of other intermediates by absorption spectroscopy. Ethane has been shown to be convenient for this purpose. The rate constant for excitation transfer from excimers to ethane in xenon was measured by the pulse-probe technique to be 3.4 x 10 ° molal s at pressures near 50 bar. Thus, addition of a small concentration of ethane can be used to reduce the absorption due to excimers to a small level at nanosecond times. 

Lxciiner lasers contain a gaseous mixture of helium, fluorine, and one of the rare gases argon, krypton, or xenon. The rare gas Is clecironically exciled by a current followed by reaction with fluorine to form excited species such as Arl. KrI, or which arc... 

In the three-body reaction (Reaction [13.5]), the Ne acts as a buffer. Given that the krypton fluoride so produced is electronically excited and has a short lifetime (about 2.5 ns), it rapidly decays by photon emission to the lower energy state as shown in Fig. 13.5. Because this is an unbound state in which the force between the atoms is always repulsive, the exciplex molecule then immediately dissociates into its constituent atoms. As a result, this state never attains a large population, and a population inversion therefore exists between it and the higher energy bound exciplex state. The decay transition can therefore be efficiently stimulated to produce laser emission. One noteworthy characteristic of this particular laser system is that it represents a rare example of a truly two-level laser. 

Homonuclear associative ionization reactions have also been observed in studies in which the ionic abundances in gas discharges are determined mass spectrometrically as functions of pressure, discharge current, and gas composition. Reaction identification is difficult in such studies because of the complexity of the multitude of excitation, ionization, neutralization, and radiative processes occurring simultaneously. Nevertheless homonuclear associative ionization reactions have been reported in dc discharges in helium, neon, 63-65) argon, 65-68) krypton, and xenon. Associative ionization reactions have also been reported in rf discharges in helium, argon, and xenon. ... 

The active medium of the KrF laser is a mixture of krypton, molecular fluorine F2, and helium or argon as buffer gas. The whole gas system can be operated in a closed cycle where the gas is pumped from a reservoir through the laser channel. In the fast discharge, excited Kr and Ar atoms and ions are formed by electron impact. The excimers are formed by several reactions, for example. 

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