I. Quenching of beta induced excited states in argon, helium and nitrogen II. Thermal electron attachment to strained molecules

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1967

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The first part of this work is concerned, with the study of the fluorescence and quenching of beta induced excited states in nitrogen, argon, and helium. The emission from nitrogen comes from N[lowered 2]([raised 3][pi][lowered g]) while in argon the emission comes from two different excited species, argon and probably water. The emission in helium is found to come from small impurities of nitrogen and the emitting species in N[lowered 2]([raised 2][sum][lowered u, raised +]). The quenching-concentration relationship is linear for the nitrogen system but non-linear for the argon and helium systems. A kinetic model has been proposed to explain the non-linear relationship through a simultaneous quenching of two excited species. In the case of the helium system this is He[lowered 2, raised +] and N[lowered 2, raised +]([raised 2][sum][lowered u, raised +]). The exact nature of the excited states in the argon system are not known. The nitrogen system follows a simple Stern-Volmer equation. The quenching rate constant for helium is 10[raised 3] to 10[raised 4] times greater than for nitrogen, which is explained as a difference between an ion molecule reaction and a molecule-molecule reaction. The relative quenching rates do not vary significantly for different compounds and for the helium system appears to be related to the polarizability and dipole moment. The system shows promise as a non-selective and non-destructive gas chromatographic detector. In the second part of the study the effect of strain on the electron affinity is discussed. Certain strained molecules in addition to having an abnormally high electron affinity exhibit an activation energy for thermal electron attachment. A high electron affinity for the strained molecules is explained as additional energy gained due to the release of strain in the negative ion. The activation energy can he accounted for hy assuming that either the electron adds to the non-planar configuration which must undergo a molecular distortion before going to the negative ion or the electron adds to an activated molecule which is distorted in the shape of the resultant negative species.

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