Photolysis in gas phase

Such techniques imply analysis of chemical products of photolysis. Application of mass-spectrometers of various types is often hampered by a number of circumstances. These difficulties will be discussed later on. The EPR method, which is currently the most extensively employed technique, features low sensitivity and is usually used for analysis of primary fragments of photolysis. For this purpose, the radicals produced are frozen on the walls of a quartz pin and are thus accumulated inside the device. On one hand, this approach allows one to overcome the sensitivity threshold of the device. However, on the other hand, this excludes the possibility of direct kinetic measurements. The SS technique permits the use of weak light sources for detecting active particles under 

As an example of application of semiconductor sensors for this purpose, we consider photolysis of simplest olefines (ethylene, propylene, acetylene, etc.) occurring in the range of vacuum ultraviolet. It is well-known (e.g., see [11]) that photolysis of ethylene may result in detachment of either hydrogen molecules (detached in one act) or hydrogen atoms. Hydrogen atoms subsequently associate into molecules or interact with ethylene molecules. In what follows, we consider how this problem can be solved with the help of sensors. 

It is well-known that hydrogen is detached from an ethylene molecule through the following reactions 

These reactions yield acetylene and hydrogen. However, it is evident that these processes result in the following secondary reactions 

To monitor a possible influence of molecular products of photolysis of ethylene (acetylene, ethane, and butane) on the sensor, a second sensor was positioned at a distance of 50 cm from the photolysis zone. The second sensor was designed to introduce corrections into the readings of the movable sensor. The specified distance was chosen so that atoms and radicals produced in the lower part of the vessel could not reach the 

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