Date of Award


Publication Type

Master Thesis

Degree Name





William McConkey




A crossed electron-molecular beam system connected to a spectrometer was used to investigate the dissociative excitation of thymine and adenine following electron impact. The emission spectrum for these molecules was measured from 80 nm to 150 nm with a 100 eV electron beam to identify the excited atomic fragments that resulted from these electron collisions. For each molecule, the hydrogen Lyman series was dominant in spectrum measurements. Relative emission cross sections were measured with respect to Lyman-alpha for each the Lyman features present in the spectrum for each molecule. The probability of obtaining other atomic fragments from the parent molecules was concluded to be insignificant. Excitation studies were also performed to measure the relative emission cross sections for electron impact energies up to 430 eV. During thymine studies, this excitation study was performed for Lyman-alpha in which the threshold energy for this feature was measured to be 23 eV. During adenine studies, excitation studies were also performed for Lyman-alpha and Lyman-beta and their thresholds were determined to be 23 eV and 18 eV, respectively. The possible excitation and dissociation mechanisms from the parent molecules that may contribute to these studied features are also discussed.