Dunning, F. B.2009-06-042009-06-041993Ling, Xuezhen. "A study of ultra-low-energy electron-molecule collisions using very-high-n Rydberg atoms." (1993) Diss., Rice University. <a href="https://hdl.handle.net/1911/16644">https://hdl.handle.net/1911/16644</a>.https://hdl.handle.net/1911/16644In the present work very-high-n Rydberg-atoms $(n \sim 100 - n \sim 400)$ are used to probe electron-molecule collisions at ultra-low electron energies. Based on the essentially-free-electron model, for sufficiently high n, Rydberg atom-molecule collisions can be described in terms of a binary interaction between the target molecule and the essentially-free Rydberg electron. Since the average kinetic energy of the Rydberg electron is ultra-low $\rm({\sim}85\mu eV - {\sim}1.4meV),$ analysis of the very-high-n Rydberg-atom collision data can provide information on electron-molecule scattering at electron energies corresponding to electron temperatures of only $\sim$1$\sp\circ$K, which are far below those accessible using any alternate approach. Rate constants for destruction of very-high-n Rydberg atoms in collisions with various target molecules have been measured. This study focuses on Rydberg electron transfer to an electron-attaching molecule which results in negative ion formation via the reactions $$\rm K({\it np\/}) + XY \to K\sp+ + (XY)\sp{-*}\ or\ \to K\sp+ + X\sp- + Y\eqno(1)$$and on rotational energy transfer from polar molecules which leads to Rydberg atom ionization $$\rm K({\it np\/}) + XY({\it J\/}) \to K\sp+ + {\it e}\sp- + XY({\it J\/}-1)\eqno(2)$$ The n dependence of the rate constants for Rydberg-atom destruction depends on the reactions involved. In reaction (1) the rate constant is independent of n whereas in reaction (2) it increases nearly linearly with n. When both reactions are possible, the measured n dependence can be explained in terms of contributions from each process. The essentially-free-electron model suggests that the n dependence of the rate constants for Rydberg-atom destruction reflects the energy dependence of the cross sections of the corresponding free electron-molecule collision processes which are $$\eqalignno{&e\sp- + \rm XY \to (XY)\sp{-*}\ or\ \to X\sp- + Y&(1\sp\prime)\cr &e\sp- + \rm XY({\it J\/}) \to {\it e}\sp- + XY({\it J\/}-1)&(2\sp\prime)\cr}$$Analysis of the data therefore provides the behavior of cross sections for these processes at ultra-low electron energies.92 p.application/pdfengCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.Atomic physicsMolecular physicsThesisThesis Sp. Sci. 1993 Ling